Twins make up 1.5% of pregnancies. This figure is on the rise due to the prevalence of IVF. All pregnancy changes are exaggerated in multiple gestations, so expect more, and more severe complaints.
- Raised age
- Family history of fecundity
- High Parity
Note that monochorionic ≠ Monozygotic, and Dichorionic ≠ Diamniotic. Depending on when splitting of ovum occurs, monozygotic twins may be mono or diamniotic.
- Average Gestation = 37 weeks. Offer elective birth from 36+0 for monochorionic twin (after course of corticosteroids) and 37+0 for dichorionic twins. Continuing uncomplicated twin pregnancies beyond 38 weeks gestation increases the risk of foetal death.
- Miscarriage risk higher in monochorionic than dichorionic twins
- 25% chance on twin disappears before any scans.
- Later loss of one twin is associated with poor outcomes for the remaining sibling.
- Congenital abnormality risk is individual, so unaffected by gestation.
Twin-Twin Transfusion Syndrome
Imbalance of arteriovenous anastamoses in monochorionic pregnancies (15%). One twin becomes overperfused, and the other underperfused.
- Underperfusion→Oligovolaemia→IUGR, Oligohydramnios
- Overperfusion→Polyvolaemia→Polyhydramnios, Heart Failure
Treat with amniocentesis of polyhydramniotic twin and laser ablation of anastamoses. Might need umbilical cord occlusion in worst case scenario.