Breastfeeding

Research www.AJOG.org

OBSTETRICS

Association between parity and breastfeedingwith maternal high blood pressureSamantha J. Lupton, BMedRes; Christine L. Chiu, PhD; Sanja Lujic, MBiostat;Annemarie Hennessy, MBBS, PhD; Joanne M. Lind, PhD

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OBJECTIVE: The objective of this study was to determine how parityand breastfeeding were associated with maternal high blood pressure,and how age modifies this association.

STUDY DESIGN: Baseline data for 74,785 women were sourcedfrom the 45 and Up Study, Australia. These women were 45 years ofage or older, had an intact uterus, and had not been diagnosed withhigh blood pressure before pregnancy. Odds ratios (ORs) and 99%confidence intervals (CIs) for the association between giving birth,breastfeeding, lifetime breastfeeding duration, and average breast-feeding per child with high blood pressure were estimated using lo-gistic regression.

RESULTS: The combination of parity and breastfeeding was associatedwith lower odds of having high blood pressure (adjusted OR, 0.89; 99%

2013;208:454.e1-7.

tween breastfeeding andContents

454.e1 American Journal of Obstetrics & Gynecology JUNE 2013

hereas there was no significant difference between mothers who didot breastfeed and nulliparous women (adjusted OR, 1.06; 99% CI,.95–1.18; P � .20). Women who breastfed for longer than 6 months

n their lifetime, or greater than 3 months per child, on average, hadignificantly lower odds of having high blood pressure when comparedith parous women who never breastfed. The odds were lower with lon-er breastfeeding durations and were no longer significant in the major-

ty of women over the age of 64 years.

CONCLUSION: Women should be encouraged to breastfeed for as longas possible and a woman’s breastfeeding history should be taken intoaccount when assessing her likelihood of high blood pressure in laterlife.

Key words: breastfeeding, cardiovascular disease, high blood
pressure, parity, women CI, 0.82–0.97; P � .001), compared with nulliparous women,
Cite this article as: Lupton SJ, Chiu CL, Lujic S, et al. Association between parity and breastfeeding with maternal high blood pressure. Am J Obstet Gynecol

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Pregnancy and breastfeeding are asso-ciated with large changes to the female

hormonal profile. A correlation betweenthese events and a woman’s risk of cardio-vascular disease has been reported sincethe 1950s1 with more recent large cohortstudies showing breastfeeding is beneficialto maternal cardiovascular health.2-5

Cardiovascular diseases are the lead-ing cause of death among women in de-

From the University of Western Sydney, Schoolof Medicine, Campbelltown, NSW, Australia.

Received Sept. 12, 2012; revised Dec. 19,2012; accepted Feb. 5, 2013.

The authors report no conflict of interest.

Presented orally at the 24th Annual ScientificMeeting of the International Society ofHypertension, Sept. 30-Oct. 4, 2012, Sydney,NSW, Australia.

Reprints not available from the authors.

0002-9378/free© 2013 Mosby, Inc. All rights reserved.http://dx.doi.org/10.1016/j.ajog.2013.02.014

For Editors’ Commentary, see

veloped countries. Hypertension is oneof the most prevalent cardiovascular dis-eases and is a strong predictor of othercardiovascular diseases including ath-erosclerosis, myocardial infarction, andstroke. Age is a powerful predictor of hy-pertension, with increasing age associ-ated with increasing rates of hyperten-sion in industrialized countries.6

The association between pregnancy andhypertension in later life remains unclear.Early work within the field found an associa-tionbetweenincreasingnumberofpregnan-cies and lower odds of hypertension,7

whereas other studies have shown no associ-ation between parity and blood pressure.8,9

These studies had relatively small samplesizes in comparison to the large cohorts thathave since been established.

Breastfeeding has been reported to confermany benefits upon the newborn, includingreduced levels of childhood obesity,10 hyper-tension,11-13 and hyperlipidemia.14,15 Morerecent studies have found an association be-

a lower risk of ma-

ternal hypertension. This was first reportedin 2005 by the Korean Women’s Cohort(KWC) Study2 and has since been reported

y the Study of Women’s Health Across theation (SWAN),3 the Women’s Health Ini-

tiative (WHI) Study,4 and the US Nurses’ealth Study II.5 No studies have examinedhether the combined effect of parity andreastfeeding is associated with high bloodressure, and how age modifies the associa-ion between breastfeeding and high bloodressure.The present study aimed to determine:

a) the association between the event ofiving birth with high blood pressure inater life, using observational data from the5 and Up Study, Australia, (b) whether theombination of giving birth and breast-eeding is associated with high blood pres-ure in later life, and (c) if the duration ofreastfeeding was associated with highlood pressure in later life, and how thisssociation is modified as women age.

MATERIALS AND METHODSThis study obtained data from women
participating in the 45 and Up Study, a
http://dx.doi.org/10.1016/j.ajog.2013.02.014

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www.AJOG.org Obstetrics Research

large scale cohort study of 267,153 menand women aged 45 and over in NewSouth Wales, Australia. Participantswere randomly selected from the Austra-lian Medicare Database, which providesnear complete coverage of the popula-tion, and they were enrolled into thestudy by completing a baseline question-naire (available at www.45andUp.org.au) and providing a signed consent form.People aged 80 years and over, and resi-dents of rural and remote areas were over-sampled. Study recruitment commencedin 2006 and was completed in 2009. The

FIGURE 1Participants included in the study

Flow chart of participant inclusion.Lupton. Parity, breastfeeding, and high blood pressure. Am J

methods for the 45 and Up Study have been

described elsewhere.16 The 45 and Uptudy received ethics approval from theniversity of NSW Human Ethics Com-ittee, and the current study was ap-

roved by the University of Western Syd-ey Human Research Ethics Committee.xposure-outcome relationships estima-

ed from the 45 and Up Study data haveeen shown to be consistent with another

arge study of the same population, regard-ess of the underlying response rate or

ode of questionnaire administration.17

All of the data used in this study wereacquired from the 45 and Up Study base-

et Gynecol 2013.

line questionnaire. Women were in-

JUNE 2013 Americ

cluded in this study if: they were age 45years or more; had never given birth orhad given birth after 18 years of age andbefore 45 years of age; had not had a hys-terectomy or both ovaries removed; andhad responded “No” to the question“Has a doctor ever told you that youhave: high blood pressure–when preg-nant?” (Figure 1).

Women were defined as having highblood pressure if they answered “Yes” tothe question “In the last month have youbeen treated for: high blood pressure.”Women were excluded if: they answered“Yes” to the question “Has a doctor evertold you that you have: high blood pres-sure – when not pregnant?” and the “Agewhen condition was first found” wasyounger than, the age reported on thequestion “How old were you when yougave birth to your FIRST child?”; an-swered “Yes” to “Has a doctor ever toldyou that you have: high blood pressure –when not pregnant?”, but were not beingtreated for high blood pressure; theyfailed to provide an age of onset for highblood pressure; they provided invaliddata for family history; or they providedinvalid data for the number of childrenthey had given birth to in their specifiedage range (Figure 1). Classification of de-mographic and lifestyle characteristicshave been described elsewhere.18

Women were classified as never hav-ing given birth if they answered “0’ to thequestion “How many children have yougiven birth to?”, with the further instruc-tion to “please include stillbirths but donot include miscarriages, please write ‘0’if you have not had any children.” Totalbreastfeeding duration was obtainedfrom the response to the question “Forhow many months, in total, have youbreastfed?”. Average breastfeeding dura-tion was obtained by dividing the totalbreastfeeding duration by the reportednumber of children for each woman.

Odds ratios (ORs) and 99% confi-dence intervals (CIs) for the associationbetween giving birth, breastfeeding, life-time breastfeeding duration, and averagebreastfeeding per child with high bloodpressure were estimated using logistic re-gression. For the analysis of whether giv-ing birth is associated with having high

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blood pressure, women who had never

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given birth were the reference group.Analysis of lifetime breastfeeding andbreastfeeding duration included onlywomen who had given birth, withwomen who had never breastfed as thereference group. Both crude and ad-justed OR were calculated and descrip-tions refer to adjusted OR unless other-wise specified. OR were adjusted fordemographic and lifestyle factors usingthe categories in Table 1, with an addi-tional category for missing values. Therewas a significant interaction betweenwhether a woman breastfed and currentage, with having high blood pressure. Asa result, women were stratified accordingto current age and divided into 3 groups(45 to �54 years, 54 to �64 years, 64years or older) when testing the associa-tion between lifetime breastfeeding andbreastfeeding duration with high bloodpressure status. All statistical tests were2-sided, using a significance level of P �01 to partially account for multiple test-ng issues.19,20 All statistical analysesere carried out using SPSS software

version 20; SPSS, Inc, Chicago, IL).

RESULTSA total of 74,785 women aged 45 andover were included in the analysis ofwhich 64,199 gave birth (85.8%), and12,456 (16.7%) reported current treat-ment for high blood pressure. Of thewomen who had given birth, 57,097(88.9%) reported they had breastfed,with the youngest women in the cohort(45 to �54 year olds) having the highest

revalence of breastfeeding (92.7%)Figure 1).

Demographic and lifestyle character-stics of women who had given birth arehown in Table 1. Women who wereorn in Australia, had an income greaterhan $30,000, consumed greater than 1lcoholic drink per week, never smoked,ad sufficient physical activity levels andad a current body mass index (BMI) of

ess than 25, had higher odds of havingreastfed. Increasing number of childrenas also associated with increased oddsf having breastfed.There was an association between par-

ty and high blood pressure, with women
ho had given birth having significantly t
454.e3 American Journal of Obstetrics & Gynecolo

lower odds of high blood pressure whencompared with women who had nevergiven birth (adjusted OR, 0.91; 99% CI,0.84 – 0.99; P � .004). Further analysis,tratifying mothers according to whether

TABLE 1Sociodemographic factors associat

Characteristics Groups

Current age, y 45 to �54...............................................

54 to �64...............................................

64�...................................................................................................................

Country of origin Australia...............................................

Other...................................................................................................................

Income �$30K...............................................

$30–$70K...............................................

$70K�...............................................

Not disclosed...................................................................................................................

Family history of HBP No...............................................

Yes...................................................................................................................

BMI �25...............................................

25-30...............................................

30�...................................................................................................................

Smoking status Never...............................................

Past...............................................

Current...................................................................................................................

Alcohol (drinks/wk) �1...............................................

1-5...............................................

6-10...............................................

11�...................................................................................................................

Physical activity Insufficient...............................................

Sufficient...................................................................................................................

Oral contraceptiveuse

Never...............................................

Ever...................................................................................................................

HRT use Never...............................................

Ever...................................................................................................................

Number of children 1...............................................

2...............................................

3...............................................

4�...................................................................................................................

BF, breastfed; BMI, body mass index; CI, confidence interval; HOR, odds ratio.a Percentages do not consistently total to 100% because of m

having breastfed; c Analysis adjusted for current age, countryalcohol consumption, physical activity, oral contraceptive us

Lupton. Parity, breastfeeding, and high blood pressure. Am

hey had breastfed, found mothers who

gy JUNE 2013

reastfed had significantly lower odds ofaving high blood pressure, comparedith women who had never given birth

adjusted OR, 0.89; 99% CI, 0.82– 0.97;� .001), whereas the odds of having

with past breastfeeding behavior

esa

column) % BFa ORc (99% CI)

361 (35) 93 1.00..................................................................................................................

454 (33) 87 0.58 (0.53–0.64)d..................................................................................................................

384 (32) 87 0.60 (0.54–0.66)d..................................................................................................................

291 (75) 90 1.00..................................................................................................................

368 (24) 86 0.78 (0.72–0.84)d..................................................................................................................

416 (26) 86 1.00..................................................................................................................

984 (25) 90 1.29 (1.17–1.42)d..................................................................................................................

472 (24) 94 2.09 (1.86–2.35)d..................................................................................................................

327 (25) 86 0.94 (0.86–1.02)..................................................................................................................

098 (48) 89 1.00..................................................................................................................

101 (52) 89 1.01 (0.94–1.08)..................................................................................................................

344 (46) 90 1.00..................................................................................................................

868 (29) 89 0.88 (0.81–0.95)d..................................................................................................................

839 (17) 86 0.69 (0.63–0.75)d..................................................................................................................

733 (65) 90 1.00..................................................................................................................

909 (28) 89 0.86 (0.80–0.93)d..................................................................................................................

272 (7) 83 0.57 (0.50–0.64)d..................................................................................................................

191 (38) 86 1.00..................................................................................................................

760 (28) 91 1.55 (1.42–1.69)d..................................................................................................................

990 (20) 91 1.52 (1.37–1.67)d..................................................................................................................

963 (12) 90 1.36 (1.22–1.53)d..................................................................................................................

792 (31) 87 1.00..................................................................................................................

407 (69) 90 1.19 (1.11–1.28)d..................................................................................................................

277 (18) 87 1.00..................................................................................................................

964 (81) 90 1.02 (0.93–1.12)..................................................................................................................

261 (69) 90 1.00..................................................................................................................

674 (29) 87 0.93 (0.87–1.01)..................................................................................................................

908 (11) 79 1.00..................................................................................................................

371 (41) 88 1.90 (1.73–2.09)d..................................................................................................................

078 (30) 92 2.94 (2.65–3.27)d..................................................................................................................

842 (18) 92 3.66 (3.24–4.13)d..................................................................................................................

high blood pressure; HRT, hormone replacement therapy;

ng values;bThe percentage of women who responded yes toigin, income level, family history of HBP, BMI, smoking status,T use, and number of children; d P � .01.

bstet Gynecol 2013.

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Cas(%

22,.........

21,.........

20,.........

48,.........

15,.........

16,.........

15,.........

15,.........

16,.........

31,.........

33,.........

29,.........

18,.........

10,.........

41,.........

17,.........

4.........

24,.........

17,.........

12,.........

7.........

19,.........

44,.........

11,.........

51,.........

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not breastfeed were not significantly dif-ferent from women who had never givenbirth (adjusted OR, 1.06; 99% CI, 0.95–1.18; P � .195) (Table 2).

Analysis including only women whohad given birth, stratified by current age,found no association between the num-ber of children a woman gave birth toand having high blood pressure. Therewas a significant association betweenlifetime breastfeeding duration and hav-ing high blood pressure. Lifetime breast-feeding duration of 6 months or greaterwas associated with lower odds of havinghigh blood pressure in women aged 45 to�64 years, when compared with parouswomen who did not breastfeed. Theodds of having high blood pressure de-creased with longer durations of breast-feeding. The lowest odds were observedin women aged 45 to �54 years whoselifetime breastfeeding duration was 24months or greater (adjusted OR, 0.58;99% CI, 0.44 – 0.77; P � .001). No signif-cant association between lifetimereastfeeding duration and high bloodressure was observed in women aged 64ears and over (Figure 2).The average breastfeeding duration

er child was also associated with havingigh blood pressure, with 3 months orore breastfeeding per child associatedith lower odds of having high bloodressure, in women aged 45 to �64ears, when compared with parous

TABLE 2Parity, breastfeeding history, and t

Variable Cases, n

Given birth..........................................................................................................

No 10,586..........................................................................................................

Yes 64,199...................................................................................................................

Given birth stratified bybreastfeeding

..........................................................................................................

No 10,586..........................................................................................................

Yes, never breastfed 7102..........................................................................................................

Yes, breastfed 57,097...................................................................................................................

CI, confidence interval; OR, odds rstio.a Analysis adjusted for current age, country of origin, incom

physical activity, family history of high blood pressure, hisment therapy use; b P � .01.


omen who never breastfed. The odds of

aving high blood pressure within theseomen decreased with longer durationsf breastfeeding per child. Within the 64ears and over age group, there was a sig-ificant association between averagereastfeeding duration per child andaving high blood pressure, only foromen who had breastfed for 18 monthsr more per child (adjusted OR, 0.38;9% CI, 0.17– 0.84; P � .002), comparedith parous women who did not breast-

eed (Figure 3).A final analysis including only partici-

ants with a family history of high bloodressure, stratified by age, found thatreastfeeding is significantly associatedith reduced odds of having high bloodressure in women aged 45 to 64 yearsTable 3).

COMMENTThis study showed the combination ofgiving birth and breastfeeding was asso-ciated with lower odds of having highblood pressure in later life, comparedwith women who had never given birth.There was no significant difference inodds of having high blood pressure inwomen who had given birth and did notbreastfeed, compared with women whohad never given birth. We also showedthat within parous women, the numberof children a woman gave birth to wasnot associated with her odds of having

odds of having high blood pressure

CrudeOR (99% CI)

AdjustedOR (99% CI)a

..................................................................................................................

1.00 (reference)..................................................................................................................

1.00 (0.93–1.07) 0.91 (0.84–0.99)b..................................................................................................................

..................................................................................................................

1.00 (reference)..................................................................................................................

1.31 (1.18–1.45)b 1.06 (0.95–1.18)..................................................................................................................

0.96 (0.89–1.03) 0.89 (0.82–0.97)b..................................................................................................................

el, body mass index, smoking status, alcohol consumption,of oral contraceptive use, and history of hormone replace-

bstet Gynecol 2013.

high blood pressure. In addition, 6

JUNE 2013 Americ

months or more lifetime breastfeedingduration, and 3 months or more averagebreastfeeding per child, were associatedwith significantly lower odds of havinghigh blood pressure in later life. The as-sociation between breastfeeding dura-tion and high blood pressure diminishedwith increasing age, demonstrating ageas a significant predictor for having highblood pressure.

Previous studies examining the associ-ation between parity and high bloodpressure have been inconclusive, withsome studies showing no association8,9

and others showing decreased odds ofhaving high blood pressure with increas-ing numbers of pregnancies.7 Our largecohort study, which included 74,785women, showed that the number of chil-dren a woman gave birth to was not as-sociated with having high blood pres-sure. Previous studies did not accountfor breastfeeding duration among themothers when examining the associationbetween parity and high blood pressureand this may explain the inconsistent re-sults between studies, because of varyingrates of breastfeeding in different popu-lations. Our study had a breastfeedingrate of 88.9% with women born outsideAustralia having lower odds of havingbreastfed (adjusted OR, 0.78; 99% CI,0.72– 0.84; P � .001) compared withwomen born in Australia. Only parouswomen who breastfed had significantlylower odds of having high blood pres-sure, when compared with nulliparouswomen. The reduced odds of havinghigh blood pressure in these women aretherefore more likely to be a result ofbreastfeeding, rather than parity alone.

Breastfeeding may modify the risk ofhaving high blood pressure through al-terations in vessel structure or in the ma-ternal hormonal and lipid profiles. Thesealterations may induce changes in thematernal cardiovascular system becauseof the repeated oxytocin exposure pro-duced by each feeding.21 Exposure to

xytocin has an inhibitory effect on ad-enocorticotropic hormones and corti-ol secretion, reducing sympathetic ner-ous system stimulation and reducinglood pressure.22 Within rats there is ev-

idence that repeated oxytocin exposure

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creasing sympathetic nervous systemdrive on both the heart and arteries, low-ering blood pressure.23 The positive so-cial interactions and emotions inducedin the mother by breastfeeding, includ-ing the touching sensation and warmthcreated by the offspring, may also havelong-term benefits to the mother’s car-diovascular health because of the psy-chologic antistress effects produced bybreastfeeding.21

The relationship between breastfeed-ing duration and blood pressure hasbeen reported in 4 large cohort studies todate.2-5 All studies have found an associ-ation between breastfeeding and mater-nal high blood pressure, with increaseddurations of breastfeeding associatedwith reduced likelihood of having highblood pressure. The WHI study was theonly study to include women over 60years of age,4 and reported that the asso-ciation between increased duration ofbreastfeeding and reduced cardiovascu-lar risk diminished as women aged. TheWHI study did not specifically examinethe interaction between age and highblood pressure. Our study supports theabove mentioned studies, and extendsthe research by showing that the associ-ation between breastfeeding duration(both lifetime and per child) and havinghigh blood pressure is only significant inwomen up to 64 years of age. The 1 ex-ception being women aged 64 years andover had significantly lower odds of hav-ing high blood pressure if they breastfedeach child for an average of 18 months ormore (OR, 0.38; 99% CI, 0.17– 0.84; P �002), compared with parous women ofhe same age who never breastfed. Theer child breastfeeding duration is re-orted in the present paper to make theesults more accessible for physiciansnd midwifes when discussing the bene-ts of breastfeeding to a mother after aingle pregnancy. A recommendation oft least 3 months of breastfeeding perhild is advocated by the authors and isore meaningful to a mother than a rec-

mmendation about how long shehould breastfeed in her lifetime.

A family history of high blood pres-ure is known to increase an individu-l’s risk of having high blood pressure,
ossibly because of the inheritance of a

umber of genetic polymorphisms thatake the individual susceptible to high

lood pressure.24 We showed thatbreastfeeding significantly reduces theodds of having high blood pressure in

FIGURE 2Association of lifetime breastfeedin

, 45 to �54 years of age, B, 54 to �64 yearsupton. Parity, breastfeeding, and high blood pressure. Am J

women with a family history of high

gy JUNE 2013

blood pressure (Table 3), up to 64 yearsof age. Women who have a family his-tory of high blood pressure could beencouraged to breastfeed their chil-dren to help delay the onset of high

with high blood pressure

ge, C, 64 or more years of age.et Gynecol 2013.

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Ageing is the single largest risk factor forhigh blood pressure because of the stiffeningof elastane in the internal lamina of arteriesandcalcificationofthearterialintima.25Both

f these factors cause an increase in periph-ral resistance, leading to an increase in theressure wave reflection and a rise in systolic

FIGURE 3Breastfeeding per child associated

A, 45 to �54 years of age, B, 54 to �64 yearsLupton. Parity, breastfeeding, and high blood pressure. Am J

lood pressure as individuals age.25,26 Our c

esults show that the benefits afforded to theardiovascular system by breastfeeding areo longer present in the majority of olderomen.The current WHO recommendations

or breastfeeding encourage breastfeed-ng for a minimum of 6 months per

ith high blood pressure

age, C, 64 or more years of age.et Gynecol 2013.

hild.27 This study provides further sup- m

JUNE 2013 Americ

ort for these recommendations, as bothhe lifetime and per child durations ofreastfeeding were associated with sig-ificant reduction in the odds of futureaternal high blood pressure. Our study

howed that 3 months or more of breast-eeding per child, and 6 months or moreifetime breastfeeding, significantly de-reased a woman’s odds of having highlood pressure, and the odds continuedo lower with longer breastfeeding dura-ions. Women should therefore be en-ouraged to breastfeed for as long as pos-ible to reduce the likelihood of highlood pressure before 64 years of age. Aoman’s breastfeeding history is also

mportant when assessing her likelihoodf having high blood pressure in later

ife.The key strength of this study is the

arge cohort size, which enabled us to ex-mine the duration of breastfeeding inifferent age groups. This study usedelf-reported data, which is prone to re-all bias, and may have led to under- orverreporting of breastfeeding duration.t has been reported in the literature thatomen who breastfeed are more likely toave a healthy BMI28 and are less likely tomoke.29 Our study showed that womenho currently had a lower BMI, hadever smoked, had sufficient levels of ex-rcise, and had a higher income wereore likely to have breastfed. Womenho breastfeed may therefore representhealthier cohort. From our data it is notossible to determine whether womenho breastfed were a healthier cohorturing their childbearing years, orhether breastfeeding results in health-

er behaviors beyond a woman’s child-earing years. Either way, there is no dif-erence in odds of having high bloodressure in women over 64 years of agehen comparing women who breastfedith women who never breastfed.In conclusion, women who breastfed

heir children had significantly reduceddds of having high blood pressure, com-ared with women who had never givenirth and varying rates of breastfeeding inifferent populations may account for in-onsistent reporting of the association be-ween parity and high blood pressure.

omen who breastfed for longer than 6

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months per child, had significantly lowerodds of having high blood pressure whencompared with parous women who hadnever breastfed. This held true in womenwith a family history of high blood pressure.The odds were lower with longer breastfeed-ingdurationsandtheassociationdiminishedin women over 64 years of age. Womenshould be encouraged to breastfeed for aslong as possible, and a woman’s breastfeed-ing history should be taken into accountwhen assessing her likelihood of high bloodpressure in later life. f

ACKNOWLEDGMENTSThe 45 and Up Study is managed by the SaxInstitute in collaboration with major partnerCancer Council New South Wales; and partnersthe National Heart Foundation of Australia(NSW Division); NSW Ministry of Health; beyon-dblue: the national depression initiative; Ageing,Disability and Home Care, NSW Family andCommunity Services; and Australian Red CrossBlood Service. We thank the many thousandsof people participating in the 45 and Up Study.J.M.L. is supported by a National Health andMedical Research Council - Australian Biomed-ical Fellowship. S.J.L. is the recipient of a Uni-versity of Western Sydney Postgraduate Re-search Award and an Ingham Health ResearchInstitute scholarship.

REFERENCES1. Winkelstein W Jr, Stenchever MA, LilienfeldAM. Occurrence of pregnancy, abortion, andartificial menopause among women with coro-nary artery disease: a preliminary study.J Chronic Dis 1958;7:273-86.2. Lee SY, Kim MT, Jee SH, Yang HP. Doeslong-term lactation protect premenopausalwomen against hypertension risk? A Koreanwomen’s cohort study. Prev Med 2005;41:

TABLE 3Breastfeeding history and high bloreported family history of blood pre

Age group, y Cases, n

45 to �54 12,730...................................................................................................................

54 to �64 11,721...................................................................................................................

64� 8650...................................................................................................................

CI, confidence interval; OR, odds ratio.a Odds ratios refer to the odds of high blood pressure among br

country of origin, income level, body mass index, smokincontraceptive use, history of hormone replacement therapy


433-8.


3. Ram KT, Bobby P, Hailpern SM, et al. Durationof lactation is associated with lower prevalence ofthe metabolic syndrome in midlife—SWAN, thestudy of women’s health across the nation. Am JObstet Gynecol 2008;198:268.e1-6.4. Schwarz EB, Ray RM, Stuebe AM, et al. Du-ration of lactation and risk factors for maternal car-diovascular disease. Obstet Gynecol 2009;113:974-82.5. Stuebe AM, Schwarz EB, Grewen K, et al.Duration of lactation and incidence of maternalhypertension: a longitudinal cohort study. Am JEpidemiol 2011;174:1147-58.6. Franklin SS, Gustin Wt, Wong ND, et al. He-modynamic patterns of age-related changes inblood pressure. The Framingham Heart Study.Circulation 1997;96:308-15.7. Ness RB, Kramer RA, Flegal KM. Gravidity,blood pressure, and hypertension among whitewomen in the Second National Health and Nu-trition Examination Survey. Epidemiology 1993;4:303-9.8. Lawlor DA, Emberson JR, Ebrahim S, et al. Isthe association between parity and coronaryheart disease due to biological effects of preg-nancy or adverse lifestyle risk factors associ-ated with child-rearing? Findings from the Brit-ish Women’s Heart and Health Study and theBritish Regional Heart Study. Circulation 2003;107:1260-4.9. Ness RB, Harris T, Cobb J, et al. Number ofpregnancies and the subsequent risk of cardio-vascular disease. N Engl J Med 1993;328:1528-33.10. Kramer MS. Do breast-feeding and delayedintroduction of solid foods protect against sub-sequent obesity? J Pediatr 1981;98:883-7.11. Martin RM, Gunnell D, Smith GD. Breast-feeding in infancy and blood pressure in laterlife: systematic review and meta-analysis. Am JEpidemiol 2005;161:15-26.12. Singhal A, Cole TJ, Lucas A. Early nutritionin preterm infants and later blood pressure: twocohorts after randomised trials. Lancet 2001;357:413-9.13. Taittonen L, Nuutinen M, Turtinen J, Uhari

pressure among women withure, stratified by age

rudeR (99% CI)

AdjustedOR (99% CI)a

.59 (0.46–0.76)b 0.68 (0.52–0.89)b..................................................................................................................

.69 (0.59–0.82)b 0.80 (0.67–0.95)b..................................................................................................................

.00 (0.84–1.18) 1.00 (0.84–1.18)..................................................................................................................

feeding compared with nonbreastfeeding women, adjusted fortus, alcohol consumption, physical activity, history of oral

and number of children; b P � .01.

bstet Gynecol 2013.

M. Prenatal and postnatal factors in predicting

gy JUNE 2013

later blood pressure among children: car-diovascular risk in young Finns. Pediatr Res1996;40:627-32.14. Owen CG, Whincup PH, Odoki K, Gilg JA,Cook DG. Infant feeding and blood cholesterol:a study in adolescents and a systematic review.Pediatrics 2002;110:597-608.15. Kark JD, Troya G, Friedlander Y, Slater PE,Stein Y. Validity of maternal reporting of breastfeeding history and the association with bloodlipids in 17 year olds in Jerusalem. J EpidemiolCommunity Health 1984;38:218-25.16. Banks E, Redman S, Jorm L, et al. Cohortprofile: the 45 and Up Study. Int J Epidemiol2008;37:941-7.17. Mealing NM, Banks E, Jorm LR, Steel DG,Clements MS, Rogers KD. Investigation of rel-ative risk estimates from studies of the samepopulation with contrasting response rates anddesigns. BMC Med Res Methodol 2010;10:26.18. Chiu CL, Lujic S, Thornton C, et al. Meno-pausal hormone therapy is associated with hav-ing high blood pressure in postmenopausalwomen: observational cohort study. PLoS ONE2012;7:e40260.19. Rothman KJ. No adjustments are needed formultiple comparisons. Epidemiology 1990;1:43-6.20. Geissinger JD. Letter: medical treatment ofsubdural hematomas challenged. Arch Neurol1975;32:69.21. Uvnas-Moberg K. Oxytocin may mediate thebenefits of positive social interaction and emotions.Psychoneuroendocrinology 1998;23:819-35.22. Amico JA, Johnston JM, Vagnucci AH.Suckling-induced attenuation of plasma cortisolconcentrations in postpartum lactating women.Endocr Res 1994;20:79-87.23. Petersson M, Alster P, Lundeberg T, Uv-nas-Moberg K. Oxytocin causes a long-termdecrease of blood pressure in female and malerats. Physiol Behav 1996;60:1311-5.24. Lupton SJ, Chiu CL, Lind JM. A hyperten-sion gene: are we there yet? Twin Res HumGenet 2011;14:295-304.25. Mitchell GF, Parise H, Benjamin EJ, et al.Changes in arterial stiffness and wave reflectionwith advancing age in healthy men and women:the Framingham Heart Study. Hypertension2004;43:1239-45.26. O’Rourke MF, Nichols WW. Aortic diame-ter, aortic stiffness, and wave reflection increasewith age and isolated systolic hypertension. Hy-pertension 2005;45:652-8.27. Feig C. Exclusive breastfeeding for six monthsbest for babies everywhere. World Health Organi-sation Online 2011.28. Lepe M, Bacardi Gascon M, Castaneda-Gonzalez LM, Perez Morales ME, Jimenez CruzA. Effect of maternal obesity on lactation: sys-tematic review. Nutr Hosp 2011;26:1266-9.29. Gerd AT, Bergman S, Dahlgren J, RoswallJ, Alm B. Factors associated with discontinua-tion of breastfeeding before 1 month of age.

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