Joachim W Dudenhausen from the Charité Berlin University Medicine and Rolf F Maier from Magdeburg University Medical Center, investigate which risks can be minimized by close monitoring in multiple pregnancies (Dtsch Arztebl Int 2010; 107: 663-8).
14 in 1000 pregnancies will be multiple pregnancies. The average term for multiple pregnancies is notably shorter (for twins, 36 weeks; for triplets, 32 weeks; and for quadruplets, 30 weeks). Causes include the greater weight carried by the pregnant woman and increased metabolism compared with a pregnancy with only one fetus. In monozygotic twins, only one placenta is present; consequently, the risk of death of one twin is higher than in dizygotic twins, where two placentas are present.
The feto-fetal transfusion syndrome affects only monozygotic twins and results in an undersupply of blood in one twin. The cause is a connecting blood vessel between the embryos, which leads to a redistribution of the blood. The treatment of choice for the syndrome is coagulation of the connecting vessel. The growth of the fetuses needs close monitoring. The fetal growth curves of head diameter and length of femur in twins are no different from those in singletons, but towards the end of multiple pregnancies, intrauterine growth is delayed. For this reason, in multiple pregnancies the delivery should be arranged after the 38th completed week of gestation.