Over the past decade, improved fertility treatments has lead to a rise in the incidence of twins, triplets and even higher-order (Quadruplets etc.) multiple pregnancies. Although most of these multiple pregnancies are fraternal (each from one egg), the incidence of identical twinning has also increased, probably due to embryo manipulation in the laboratory.
Fertility treatments utilize hormonal injections that increase the number of eggs produced. Following hormone injections, a woman can be artificially inseminated, or undergo in-vitro fertilization whereby the eggs are fertilized in the laboratory and actual embryos are transferred into the uterus.
Multiple pregnancies are considered high-risk pregnancies. For the mother, the risks include increased chance of hypertension in pregnancy, gestational diabetes, cesarean section and hemorrhage at the time of delivery. For the babies, the main risks relate to preterm delivery and the risk of disability or death from underdeveloped organs.
