Ultrasound Obstetrics

Diagnosis and confirmation of early pregnancy-

Gestational sac can be visualized at four and a half weeks
Embryo can be measured at 5 and a half weeks
Confirmation of pregnancy in uterus vs ectopic vs molar

Vaginal bleeding in early pregnancy-

Heartbeat can be detected by dopplar at 6-7 weeks (if seen 95% likely continued pregnancy)
Normal 6 week (90-110) 9 week (140-170) 5-8 weeks below 90 high risk of miscarriage
Detection of missed abortions and blighted ovum (anembryonic pregnancy)
Repeat ultrasound in 7-10 days to confirm

Determination of gestational age and fetal size-

Crown Rump Length- 7-13 weeks (more reliable for dating)
Biparietal Diameter- (less reliable for dating but do as early as possible)
Femur Length- (less reliable for dating but do as early as possible)
Abdominal Circumference- (best reflection of fetal size and weight)
Gestational sac diameter- (less reliable for dating)
Yolk sac diameter- max at 7-11 weeks, larger/ above 5.6mm before 10 weeks abnormal outcome
Head circumference- like BPD but compensates for abnormal head shape
Nuchal skin fold- Sign of skin edema, increased in Down, Turner, other xsome abnormalities (between 10-13 weeks normal fold is below 3mm and 16 weeks below 6-7cm)

Fetal malformation-

Can be made before 20 weeks
Hydrocephalus, anencephaly, myelomeningocoele, achondroplasia/ other dwarfism, spina bifida, gastroschisis, duodenal atresia, fetal hydrops.
Better equipment- cleft lip/ pallete, cardiac anomalies.

First Trimester “soft markers” for Downs-

Absence of nasal bone 11-13 weeks/ nuchal translucency

Assist in amniocentesis, chorionic villus sampling, cordocentesis

 Placental Localization-

Exclude placenta previa, placental abnormalities in diabetes, fetal hydrops, Rh isoimmunization, IUD

Number of pregnancies-

Chorionicity, fetal presentations, growth retardation/anomaly, twin/twin transfision.

 Oligy.hydramnion- AFI

Evaluation of biophysical profile (movements/tone/breathing)

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