In the name of God

DR. MojibinaObstetrician & Gynecologist

• Preparation to scan:

1-Orientation2-Magnification

3-Gain

•First trimester overview

•11 weeks-13weeks+6days

Or•CRL 45 -84 mm

THE 18-23 WEEKS SCAN

• Ideally all women should be routinely offered a scan at 18

– 23 weeks of gestation.

• Prior to starting the scan, confirm if the patient has had Down syndrome screening. If screening declined, discuss

with the patient if they wish to be notified about the presence

of markers of aneuploidy.

Objectives of the scan

• To confirm fetal growth (and gestational age)

• To check for major structural anomalies • To check for markers of chromosomal

abnormality • To determine the risk of preterm labour

(cervical length) • Number of fetuses, fetal presentation, fetal

heart action • Placental localisation, amniotic fluid volume,

number of cord vessels

Measurements: • Biparietal diameter (BPD) • Occipito frontal diameter (OFD) • Posterior horn of lateral ventricle • Transverse cerebellar diameter (TCD) • Cisterna magna (CM) • Nuchal fold thickness • Nasal bone length • Abdominal circumference (AC) • Femur length • Humerus length

•The following views of the

fetus should be obtained:

•Head & Brain

• BPD view to demonstrate the septum cavum

pellucidum (otherwise suspect absent corpus callosum) and examine both lateral ventricles

• Sub-occipitobregmatic view to examine cerebellum and

vermis

Face• Mid-sagittal view of face (profile) to

confirm presence of the nasal bone and exclude micrognathia

• Transverse view of the orbits to exclude microphthalmia

• Transverse view of the upper lip with anterior palate to exclude cleft lip Mid-sagittal view of face (profile) to confirm presence of the nasal bone and exclude micrognathia

Spine•Views of spine: sagittal, coronal and transverse (all vertebrae)

Thorax• Transverse sweep through chest and down to fetal stomach to exclude mediastinal

• shift and cystic lung lesions and establish situs of heart and stomach

Heart• Sweep through heart in transverse plane to include 4-chamber view, outflow tracts,

• 3-vessel view

Abdomen• Transverse view of the abdomen

to demonstrate normal stomach • Longitudinal view of the abdomen

to examine the cord insertion and demonstrate the bladder

• Transverse view of the abdomen with spine up to demonstrate both kidneys and renal pelvises

Extremities• Upper limbs – follow both limbs from shoulder to hand noting length and normality of long bones and digits. At least one hand should be seen unclenched and middle

• phalanx of 5th digit seen

Extremities• Lower limbs – again follow both limbs

from hips to feet to confirm symmetry in long

• bone length and joint positions. A coronal or sagittal view of both ankles should be

• seen to exclude talipes. A ‘sole-print’ view of each foot should be obtained.

placenta If the placenta covers the

internal cervical os or the lower border of the placenta is within 2 cm of the os the placental position should be determined transvaginally at

32 weeks.

Two vessel cord

• If this is an isolated finding reassure parents that this is found in 1 in 200 normal pregnancies. In about 10% of cases there is poor fetal growth in the third trimester (compared to 5% for the average population). These patients will have the routine 31-32 weeks scan and a growth scan at 36 weeks.

Cervical length of 15 mm or less

• In the sub group with cervical length of <15 mm the women should be offered prophylactic administration of progesterone (vaginal pessary of 200 mg/night) from 22 to 34 weeks, which reduces the rate of early preterm delivery by about 25%.

THE 31-32 WEEKS SCAN

• Ideally all women should be routinely offered a scan at

31+0 – 32+6 weeks of gestation.

Objectives of the scan

To asses fetal growth and wellbeing

To check for major structural anomalies

To check placental position To check number of umbilical

arteries

Assessment The fetal anomaly screen should be

completed in all cases. Fetal parts that cannot be examined should be

recorded as ‘not examined’. Assess growth velocity by reviewing

HC, AC, FL and EFW charts Measure the deepest vertical pool of

amniotic fluid or AFI

Scans after 32 weeks

• SGA, LGA, oligo and polyhydramnios, SUA at the 31-32 weeks scan

• Suspected SGA, LGA, oligo and poly from clinical examination after 34 weeks

• Diabetes mellitus pre and gestational: 36 weeks. In addition to HC, AC, FL and Amniotic fluid (deepest pool) record the thickness of the fat layer in the standard AC view and note any obvious thickening of the interventricular septum of the heart.

Indications for

cardiac scan

• Suspicion of cardiac malformation on scan

• Referral to HBR specifically for suspected heart defect

• Increased NT (above 95th centile) or tricuspid regurgitation at 11-13 wks

• Fetal hydrops • Monochorionic twins • Family history (mother, father,

child/fetus) of heart defect • Maternal insulin dependent diabetes

mellitus • Maternal epilepsy currently on anti-

epileptic medication • Maternal anti-Ro antibodies

Thank You

Very much

ForYour

attention

Trisomy 13:• Holoprosencephaly, microcephaly, facial

abnormalities, cardiac abnormalities, enlarged and

echogenic kidneys, exomphalos and post axial

polydactyly

Triploidy• When there is double paternal

contribution there is a molar placenta and the pregnancy rarely persists beyond

20 weeks. When there is a double maternal contribution the placenta is thin

but of normal consistency and the pregnancy may persist into the third

trimester. The fetus demonstrates severe asymmetrical growth restriction, mild

ventriculomegaly, micrognathia, cardiac abnormalities, myelomeningocoele,

syndactyly, and 'hitch-hiker' toe deformity

Turner syndrome:• Large cystic hygromas,

generalised edema, mild pleural effusions and ascites,

cardiac abnormalities and horseshoe kidneys, which are

suspected by the ultrasonographic appearance of bilateral mild hydronephrosis

Markers of aneuploidy

• Screening for chromosomal abnormalities is primarily by the first trimester combined test and in those

who book late by the second-trimester quadruple test. However, a

series of major or minor abnormalities detected at the 20-23 weeks scan

may modify the risk derived from the previous screening test.

• In the second trimester scan each chromosomal defect has its own syndromal pattern of detectable

abnormalities. Therefore, when an abnormality is detected a thorough check should be made for the other features of the chromosomal defect

known to be associated with that marker:

Trisomy 21:• Nasal hypoplasia, nuchal fold

thickness, cardiac defects, intracardiac echogenic foci,

duodenal atresia and echogenic bowel, mild hydronephrosis,

shortening of the femur, sandal gap and clinodactyly or mid-

phalanx hypoplasia of the fifth finger

Trisomy 18:• Strawberry-shaped head, choroid plexus

cysts, absent corpus callosum, enlarged cisterna magna, facial cleft, micrognathia,

nuchal edema, heart defects, diaphragmatic hernia, esophageal atresia, exomphalos, single umbilical artery, renal

abnormalities, echogenic bowel, myelomeningocoele, growth restriction and

shortening of the limbs, radial aplasia, overlapping fingers and talipes or rocker

bottom feet