8.7  Multiple pregnancy

In this section, we turn to the subject of multiple pregnancy, when there is more than one fetus in the uterus. More than 95% of multiple pregnancies are twins (two fetuses), but there can also be triplets (three fetuses), quadruplets (four fetuses), quintuplets (five fetuses), and other higher order multiples with a declining chance of occurrence. The spontaneous occurrence of twins varies by country: it is lowest in East Asian countries like Japan and China (1 out of 1000 pregnancies are fraternal or non-identical twins), and highest in black Africans, particularly in Nigeria, where 1 in 20 pregnancies are fraternal twins. In general, compared to single babies, multiple pregnancies are highly associated with early pregnancy loss and high perinatal mortality, mainly due to prematurity.

8.6.3  Complications of shoulder presentation

8.7.1  Types of twin pregnancy