Multiple pregnancy · OBGynSpace

Maternal

Anaemia, hypertension, gestational diabetes are all more likely: Anaemia, hypertension, gestational diabetes are all more likely
Hyperemesis and preterm labour symptoms asked at every visit: Hyperemesis and preterm labour symptoms asked at every visit
Delivery plan: mode by presentation of the first twin
Third stage: two placentas to inspect, more oxytocin ready

Fetal

Chorionicity fixed in the first trimester: the lambda or T sign
Growth every 4 weeks (dichorionic) or 2 weeks (monochorionic): Growth every 4 weeks (dichorionic) or 2 weeks (monochorionic)
Twin to twin transfusion screening: fluid and bladders in monochorionic twins
Two heart rates traced separately in labour: Two heart rates traced separately in labour

Chorionicity first

Established before 14 weeks: two sacs with a thick membrane and the lambda (twin peak) sign are dichorionic; a thin membrane with a T-shaped insertion is monochorionic diamniotic; no membrane is monochorionic monoamniotic.
Monochorionic twins share a placenta with vascular anastomoses: twin-twin transfusion syndrome in 10 to 15 percent, twin anaemia-polycythaemia sequence, selective growth restriction, and the risk to the survivor if one dies.
Surveillance: dichorionic every 4 weeks from 24 weeks; monochorionic every 2 weeks from 16 weeks (liquor in each sac, bladders, Doppler).

Dichorionic diamniotic twin pregnancy

Transvaginal, 8 weeks. Two gestational sacs, each with an embryo.

Higher risks of hyperemesis, anaemia, preeclampsia (aspirin from 12 to 16 weeks), gestational diabetes, preterm birth (about half deliver before 37 weeks), and postpartum haemorrhage.
Timing: uncomplicated dichorionic twins at 37 to 38 weeks; monochorionic diamniotic at 36 to 37; monoamniotic at 32 to 34 by caesarean.
Mode: vaginal birth is reasonable when the first twin is cephalic and the team is experienced with the second twin's delivery (which may need internal podalic version or breech extraction). Continuous monitoring of both.