Ultrasound is a medical imaging technique that uses high-frequency sound waves to create images of internal organs and structures of the body. In obstetrics, ultrasound is used to assess the growth and development of the fetus, confirm pregnancy, determine due date, detect multiple pregnancies, diagnose certain birth defects, and monitor the well-being of the fetus. It is a non-invasive and safe procedure that can be performed throughout pregnancy. Ultrasound can be done transabdominally or transvaginally, depending on the gestational age of the pregnancy and the information needed.

1. Role of ultrasound in
obstetrics
MAHMOUD AL-JUBEH
OBGYN SPECIALIST

2. Role of ultrasound
 date pregnancies
 Number , size of sac , size of the fetus (CRL )
 Identify multiple gestation , fetal heart , diagnose miscarriages
 Placental location and type
 monitor growth of the fetus (fetal growth , amniotic fluid )
 identify congenital abnormalities (detailed anomalies scan )
 Colour doppler assess the fetal and placental vessels (placental function )
& many others …..

3. Ultrasound
 Above sound wave frequency , from 3.5 (abdominal) to 7 MHZ (vaginal)
 ‘acoustic impedance’: is a physical property of tissue. It describes how much
resistance an ultrasound beam encounters as it passes through a tissue.
 Transvaginal is useful in : obese patients , first trimester , cervical length
 Transabdominal ultrasound after the first trimester
 3D and 4D in detailed anomalies scan
 Doppler ultrasound allows the assessment of the velocity of blood within fetal
and placental vessels and provides indirect assessment of fetal and placental
condition.

4. Diagnosis and confirmation of viability in early
pregnancy
 Gestational sac : 4-5 weeks (4+3)
 Yolk sac : 5 weeks (5+3)
 Fetal pole : 5-6 weeks (5+3)
 Fetal heart beat : 6 weeks
Help in identifying sac number (multiple pregnancy )
Presences of the sac ( ectopic pregnancy ?)
Diagnosis of miscarriage (missed , incomplete , complete , threatened )

6. Gestational age and fetal growth assessment
 Parameters used for gestational age assessment :
A. CRL (before 14 weeks )
B. Head circumference (after 14 weeks )
C. Others : femur length , biparietal diameter
the most accurate is CRL in the first trimester
 Fetal growth is assessed by abdominal circumference or EFW using HC, AC, FL,
PBD, important to diagnose IUGR, SGA …….

7. Abdominal
circumference
Femur length
Head circumference
and biparietal
diameter

8. Role of ultrasound in multiple pregnancy
 Identify number of sacs
 Identify chronicity ( best between 9-10 weeks )
 Dichorionic twins has thicker septum and lamda sign
 Monochorionic twins has thiner septum and T sign
 Fetal sex difference maybe used (dizygotic so always dichorionic)

9. T sign and Lambda sign

10. Diagnosis of fetal abnormality
 Dating scan :
o first trimester scan , its useful in identifying skeletal ,cardiac, abdominal wall , neurological defects as spina bifida and
anencephalies
o From 10 -14 weeks
o Involves in addition, gestational age , scan numbers , identify chronicity , viability and NT
 Second trimester anomaly scan
this is done between 18-21 weeks
detection rate of 40-90 % of anomalies (general incidence of 2-3 %)
 Presence of some (soft markers) increases the possibility of congenital and genetic disorders ( as increased nuchal
translucency , nasal bone hypoplasia , sever early IUGR ,duodenal obstruction …)

11. Placental localization
 Help to identify placenta previa
 Help to identify abnormal placentation
 20% of women have a low-lying placenta at 20 weeks, and only 10% of them
remains to term

13. Amniotic fluid assessment
 Single deepest pocket
o normal between 2-8 cm , more than 8 is polyhydramnios , less than 2 cm is
oligohydramnios
• Maximum amniotic fluid at 35 weeks the plateaus
 Amniotic fluid index AFI
• the sum of 4 quadrant vertical pocket
• normal from 5-25 cm , less than 5 is oligohydramnios and more than 25 is
polyhydramnios

15. Measurement of cervical length
 We assess the length of the cervix from internal to external os
 Screening is for high risk group from 16 weeks (history of second trimester loss)
 Cut off is 25 mm , patients with less than this will have
a 50 % chance of preterm labor before 34 weeks
 Transvaginal ultrasound is used

16. Fetal heart tone position