MULTIPLE GESTATION

incidence of twins is 1/80 and triplets 1/6400
2/3 of twins are dizygotic (i.e. fraternal)
hereditary factors (on maternal side only) and fertility drugs/procedures affect the dizygotic twins rate only
monozygous twinning occurs at a constant rate worldwide (1/250)
determination of zygosity by number of placentas, thickness of membranes, sex, blood type

Classification of Twin Pregnancies

Monoamnionic Monochorionic (forked Cord)

Monoamnionic Diamnionic Monochorionic

Diamnionic Monochorionic

Diamnionic Dichorionic (fused)

Diamnionic Monochorionic Dichorionic (separated)

Monoamnionic Monochorionic (Double Monster, one cord)

Complications Associated with Multiple Gestation

Maternal	Maternal-Fetal	Fetal
1. hyperemesis gravidarum 2. DM 3. preeclampsia / PIH 4. PPH (uterine atony) 5. placental abruption 6. anemia (increased iron and folate needs) increased physiological stress on all systems 7. increased compressive symptoms 8. C-section	1. increased PROM / PTL 2. polyhydramnios 3. umbilical cord prolapse 4. placenta previa	1. prematurity* 2. IUGR 3. mal presentation 4. congenital anomalies 5. twin-twin transfusion (DA/MC) 6. increased perinatal morbidity and mortality 7. twin interlocking (win A breech, win B vertex) 8. single fetal demise

Management

rest in T3
increased antenatal surveillance
close monitoring for growth (serial ultrasounds)
vaginal examinations in third trimester to check for cervical dilatation
may attempt vaginal delivery if twin A presents as vertex, otherwise C-section
twin B should be delivered within 15-20 minutes after twin A (may be longer if FHR tracing adequate)