Obstetric sonography

lec. 1 U/S

Dr. Lina Hammad Level 9

• Obstetric sonogaphy is usually obtained twice during normal pregnancy

calculated from LMP• 18 - 22 weeks. (1st scan in 2nd trimester)

• 32 – 36 weeks. (2nd scan in 3rd trimester)

Indication for 1st scan (18-22week)

• Measurement of gastational age.• Diagnose multiple pregnancy.• Diagnose fetal abnormality.• Locate placenta• Recognize pelvic masses that will interfere

with the pregnancy myomas.

Indication for 2nd scan (32 - 36week)

• Diagnose intrauterine growth retardation.• Diagnose fetal abnormality.• Confirm the presentation and position of the

fetus.• Locate the placenta more accurately.• Assess the amount of amniotic fluid.• Exclude complication.

Indication for an early (pre 18 weeks) ultrasound

• To confirm pregnancy and it’s location (intra / extrauterine)

• Estimation of gestational age.• To identify multiple pregnancies.• Exclude molar pregnancy.• Exclude pseudo-pregnancy.• To diagnose pelvic masses.

1st trimester scaning

Afetus between 11- 13 weeks of age for nuchal translucency

measurement .

Normal early pregnancy (18 weeks)

• Gestational sac.• The embryo.• Yolk sac.• Corpus luteum• Multiple pregnancy.• IUCD

Gestational sac• Ahypoechogenic sac

surrounded by double echogenic ring.

• Seen at 5-6 weeks of pregnancy

• Estimation of gestational age from G.sac volume is done.

The embryoVisible at 8 week. (Echogenic area within the G.sac

With cardiac motion).

Movement of the embryo and fetal head is observed seen >9-10 week

The skull is visible from 12 week.

Yolk sac

• Occasionally seen 7-11 weeks.

• Around cystic structure adjacent to the fetus.

• 4-5mmøIntrauterine pregnancy at 8 weeks' gestation, demonstrating embryo (E) and yolk sac (YS).

Corpus luteum

Can be seen until 12th week up to 4 cmø can rupture causing hemorrhages

Multiple pregnancy

• Can be seen at 8 weeks• Have to be confirmed after

14 weeks. (18 – 22 weeks) as not all

G.sac contains viable embryo.

IUCD

• Locate the IUD location, if inside the uterus:• IUD well away from G.sac. (no interferance)

• IUD string is seen in vagina. (IUD will be removed) • Abortion might occur especially if IUD is near

to implantation site.