Prenatal Development

What are some early signs of pregnancy?

From Conception to BirthPeriod of the Zygote Period of the EmbryoPeriod of the Fetus

Period of the ZygoteBegins when egg is fertilized in the fallopian tube.

Period of rapid cell divisionEnds 2 weeks later when the zygote is implanted in the wall of the uterus

Period of the Zygote

Period of the EmbryoFrom 3 to 8 weeks after conceptionBody parts are formed during this period

Embryo rests in the amnion filled with amniotic fluid

Umbilical cord joins embryo to placenta

Prenatal Structures

Period of the FetusFrom 9 weeks after conception to birth

Increase in size and systems begin to function

Age of viability: 22 to 28 weeks

First MonthBy the end of the

first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

First Month

Two MonthsThe embryo is about

1 inch long and has distinct, slightly webbed fingers. Veins are clearly visible. The heart has divided into right and left chambers.

Two Months

Three MonthsBy now the fetus is 2 1/2

to 3 inches long and is fully formed. He has begun swallowing and kicking. All organs and muscles have formed and are beginning to function.

Four MonthsYour baby is

covered with a layer of thick, downy hair called lanugo. His heartbeat can be heard clearly. This is when you may feel your baby's first kick.

4 months

Five Months A protective coating

called vernix caseosa begins to form on baby's skin. By the end of this month, your baby will be nearly 8 inches long and weigh almost a pound.

Six MonthsEyebrows and

eyelids are visible. Your baby's lungs are filled with amniotic fluid, and he has started breathing motions. If you talk or sing, he can hear you.

6 Months

Seven MonthsBy the end of the

seventh month, your baby weighs about 3 1/2 pounds and is about 12 inches long. His body is well-formed. Fingernails cover his fingertips

Eight MonthsYour baby is gaining

about half a pound per week, and layers of fat are piling on. He has probably turned head-down in preparation for birth. He weighs between 4 and 6 pounds.

Nine MonthsYour baby is a hefty

6 to 9 pounds and measures between 19 and 22 inches. As he becomes more crowded, you may feel him move around less.

Influences on Prenatal DevelopmentGeneral Risk FactorsTeratogens: Diseases, Drugs, and Environmental Hazards

How Teratogens Influence Prenatal Development

Prenatal Diagnosis and Treatment

General Risk FactorsNutrition: adequate amount of food, protein, vitamins, & minerals

Stress: decreases oxygen to fetus and weakens mother’s immune system

Mother’s Age: neither too young, nor too old

Teratogens: Diseases, Drugs, and Environmental Hazards

• Many diseases pass through the placenta directly and attack the fetus

• Potentially dangerous drugs not limited to cocaine but include alcohol and caffeine

• Environmental hazards are treacherous because we’re often unaware of their presence

How Teratogens Influence Prenatal Development

Not universally harmfulHarm particular structures at a particular point in development in particular animals

Effects of Teratogens

Prenatal Diagnosis and Treatment

Diagnosis: ultrasound, amniocentesis, and chorionic villus sampling can detect physical deformities and genetic disorders

Treatment: fetal medicine and genetic engineering are experimental

Prenatal Diagnosis

Amniocentesis Chorionic Villus Sampling

Labor and DeliveryStage 1: starts when the muscles of the uterus contract and ends when the cervix is fully enlarged (about 10 cm)

Stage 2: baby is pushed down the birth canal

Stage 3: placenta is expelled

Three Stages of Labor

Approaches to Childbirth• Childbirth classes

provide information about pregnancy and childbirth

• Childbirth classes teach pain control through deep breathing, imagery, and supportive coaching

• Mothers who attend classes use less medication during labor and feel more positive about labor and birth

Birth Complications• Lack of oxygen (anoxia): Often leads to surgical removal of the fetus (C-section)

• Premature and Small-for-date infants

• Prematurity is less serious than small-for-date

The Newborn• Assessing the

newborn: Apgar to assess newborns’ health; NBAS for a comprehensive assessment of infants

• 4 primary states: alert inactivity, waking activity, crying, sleeping

• Half of newborns’ sleep is REM (deep sleep)

• Putting the baby to sleep on their back may prevent SIDS

Postpartum DepressionHalf of all new moms feel some irritation, resentment, and crying

10-15% feel more severe postpartum depression

Postpartum depression affects warmth and enthusiasm of mothering

Happy Birthday!!!