Multiple pregnancy, or more correctly multi-fetal pregnancy, can occur naturally at a chance of 0.5-1%.
However, it has become more common as a result of popular use of assisted reproductive technology (ART).
Hence the overall incidence of multiple pregnancies varies with localities, and it is about 1.5 to 2% in Hong Kong.
Multiple pregnancies are associated with higher fetal, maternal and obstetric complications when compared to singleton pregnancies.
Hence iatrogenic multiple pregnancies should be prevented by limiting the number of embryo transfer to one, and not more than two in any situation.
At undergraduate levels, medical students should focus on twin pregnancy (and triplet pregnancy if they are siting for distinction assessment).

C6-1 – Zygosity and chorioamnionicity in twin pregnancy – Dizygotic and Monozygotic

C6-2 – Zygosity and chorioamnionicity in twin pregnancy – Monozygotic (MZ)

C6-3 – Fetal risk

C6-4 – Differentiation of fetal gender by USG assessment of the externa genitalia

C6-5 – Inter-twin membrane septum and its insertion site in DCDA & MCDA twins

C6-6 – Genetic screening and diagnosis in twin pregnancies

C6-7 – Staging of TTTS

C6-8 – Timing of delivery of twin pregnancies