The Role of Ultrasound in Obstetric and Gynaecology

1. The Role of Ultrasound in Obstetric and Gynaecology Max Brinsmead PhD FRANZCOG May 2006

2. Potential uses for ultrasound in obstetrics 1: • Locate the pregnancy – exclude ectopic • Assess viability – assessment of threatened miscarriage • Determining gestation & dates • Crown rump length • Diagnosis of twins – the importance of zygosity • Assessment of other pelvic masses • e.g. fibroids, functional ovarian cysts & neoplasms • Screening for abnormalities first trimester • Nuchal fold measure, anencephaly etc. • Assisting CVS and amniocentesis • Diagnosis of molar pregnancy

3. Potential uses for ultrasound in obstetrics 2: • Second trimester dating (+/- 10 days) • Biparietal diameter, head & abdominal circumference, femur length • Screening for abnormalities • e.g. spina bifida, cardiac, renal • Screening for placenta previa • Cervical length monitoring • >30 mm before 18w & >25 mm before 28 w = low risk of pre term delivery • Assessment of APH • Assessment of fetal growth • Asymmetrical and symmetrical • Evaluation of polyhydramnios and hydrops

4. Potential uses for ultrasound in obstetrics 3: • Assessment of fetal welfare • Amniotic fluid index or deepest pool • Fetal breathing • Fetal movements and tone (the Biophysical Profile) • Doppler flow studies • In umbilical arteries • Fetal middle cerebral artery • Uterine arteries • Diagnosis and management of malpresentation • Breech and unstable or transverse lie • Directing intrauterine interventions • e.g. transfusion for hydrops, catheter for urethral stricture • Placental grading (of doubtful value) • Assessment of the postpartum uterus

5. Proven uses for ultrasound in pregnancy: • Dating the gestation • 30% of women cannot provide a LMP • Another 25% have a LMP that is >2w different from USS dates • When dates are known aneuploidy screening is accurate and errors of delivery are avoided, fewer inductions for post dates etc. • Identification of multiple pregnancy • Twins have a perinatal mortality that is 2-4x singletons • Monitoring for discordant growth with Doppler reduces risk • Identification of breech in the third trimester • ECV reduces the rate of Caesarean section • Few RCTs of routine ultrasound have shown any effect on overall perinatal mortality and morbidity

6. Unproven uses for ultrasound in pregnancy: • Screening for Aneuploidy • Cost effectiveness of universal screening debated • Ethical issues and patient choice involved • Screening for structural malformations • Sensitivity is 13 – 50% depending on expertise & equipment • And only half of these before 20 w gestation • False positives occur • Screening for IUGR in the 3rd trimester • Sensitivity is 80-90% • But the positive predictive value of neonatal morbidity is only 25-50% • The rest have constitutional smallness

7. Harmful Effects of ultrasound in pregnancy: • It is not ionising radiation • However, thermal effects and cavitation can occur in tissues exposed to high power ultrasound • One RCT of repeated routine ultrasound with Dopplers in the 3rd trimester found a small but significant decrease in birth weight in the exposed cohort

8. Potential uses for ultrasound in gynaecology 1: • Assessment of adnexal pelvic masses • Compound B scan • Doppler vessel studies • Diagnosis of polycystic ovaries • Investigation of postmenopausal bleeding • Imaging and measure of endometrial thickness • Investigation of menorrhagia • Fibroids and adenomyosis • Monitoring of follicle number and growth for IVF • Egg recovery for IVF and ICSI • Evaluation of pelvic pain • A limited role • Screening for ovarian cancer • Too many false positives

9. Potential uses for ultrasound in gynaecology 2: • IUCD and Implanon location • Treatment of ovarian cysts (aspiration) and ectopic pregnancy (methotrexate) • Saline hysterography for delineation of the uterine cavity • Tubal patency studies in infertility • Evaluation of primary amenorrhoea