Multiple Pregnancy

1. Multiple Pregnancy Max Brinsmead PhD FRANZCOG January 2012

2. Incidence of Multiple Pregnancy • Twins 1:80 in Caucasians • Assisted conception (IVF) explains most of the increasing incidence • But incidence is also affected by: • Race (1:50 Black Africans, 1:150 in Asians) • Family history (mean FSH levels) • Older maternal age • Increasing parity • Spontaneous triplets 1:6400 (Hellin’s Law)

3. Why are Multiples a Problem? • Prematurity • Risk of pre term delivery twins increased 5-fold • And 10-fold for triplets • 14% twins and 41% triplets born very pre-term • Intrauterine growth restriction • Often manifest as discordant growth • Congenital malformations increased 2-fold • In monochorionic twins only • Increased rate of maternal pregnancy disorders • e.g. Pre eclampsia, gest. Diabetes, APH etc • Overall PN mortality increased 2 – 3-fold

4. But the single most important predictor of Risk in a twin pregnancy Is Chorionicity

5. Types of twin pregnancy • Dizygotic – arise from two eggs. • These are non-identical twins • Monozygotic – one egg or embryo that splits • These are identical twins (clones) • But from a clinical perspective it is chorionicity that is important • Dichorionic (two chorion, separate sacs and placentas) • Monochorionic (one chorion and a shared placenta) • Monochorionic and diamniotic (separate sacs) • Monochorionic and monamniotic (only 1%) • About 1/3 twin pregnancies are monochorionic

6. Early Diagnosis is Important • The early diagnosis of twins is one of the reasons to advocate universal 1st trimester scans • There are implications for prenatal screening for aneuploidy • AND • It is the best time to document chorionicity • By looking for and studying the gestational sac(s) • “Y” sign = dichorionic • “T” sign = monochorionic • If in doubt refer for specialist scanning before 14 weeks

7. Monochorionic Twin Problems • Almost all monochorionic twins share vessels in their common placenta • But for 10 – 15% unidirectional flow results in twin-to-twin transfusion (TTS) which can: • Cause discordant growth • Has cardiovascular , haematological and amniotic fluid burdens • Result in the death of one twin • And a high risk of neurological damage to the survivor • MC and MA twins • Are at high risk of cord entanglement • Or succumb to acute polyhydramnios in the 2nd trimester

8. Management of Twin Pregnancy Patient counselling Issues of prenatal diagnosis Nutrition and rest More frequent AN visits Dealing with the discomforts of pregnancy Place of delivery Timing of delivery Mode of delivery Rearing twins A role for Support Groups

9. Management of Twin Pregnancy • Scan MC twins every 2 – 3 weekly from 16w • Best outcomes from TTS occur if it is diagnosed <24 wks • Refer to a Perinatal Centre • IUFD of one twin also requires Perinatal Centre review • Scan MC twins at 22w for cardiac defects • Scan DC twins at 28, 34 and 36w • or as clinically indicated • Add Doppler flow studies of umbilical artery • Cervical length monitoring? • Low threshold for admission • But routine “bed rest” long abandoned

10. When to Deliver? • NICE Recommendations: • 35 completed weeks for monochorionic twins • 37 completed weeks for dichorionic twins • The ANZ RCT of elective IOL at 37 weeks vs standard care • 235 women in multiple centres • Stopped early through lack of funding • Fewer SGA infants from IOL (RR = 0.39, CI 0.20 – 0.750 and a trend towards fewer adverse infant outcomes (death, serious trauma, seizures, NICU admission >4 days etc) • Because of the very poor prognosis associated with MCMA pregnancies many perinatologists recommend: • El CS at 32w after steroids

11. Management of Twin Labour Elective CS for a leading twin breech A role for epidural anaesthesia (but not mandatory) IV line. Group and save Continuous monitoring if there is any other complication e.g. premature or discordant Second twin requires presence of an obstetrician & someone capable of neonatal resuscitation Take steps to deliver 2nd twin within 20 – 40 min PPH prophylaxis Consider thromboprophylaxis