The Future of Children, Princeton - Brookings: Providing research and analysis to promote effective policies and programs for children.

Within the past decade, the American public has seen a rise in multifetal pregnancies as a result of widespread use of infertility therapies such as ovulation-inducing drugs, in vitro fertilization, gamete intrafallopian transfer, and zygote intrafallopian transfer. For example, in the United States in 1990, 5,193 babies were born with the aid of infertility therapies. Of those, 981 sets were twins, 158 sets were triplets, 12 were quadruplets, and 2 were quintuplets.⁵²

Unfortunately, the risks of perinatal mortality and morbidity and of maternal morbidity increase in multifetal pregnancies. The most common complication is preterm delivery, with twins having an average gestational age at delivery of 36 to 37 weeks; triplets, 34 weeks; quadruplets, 29 to 31 weeks, and quintuplets, even earlier.^53-57 In addition, researchers have shown an increased incidence of low birth weight, gestational diabetes mellitus, pregnancy-induced hypertension, and greater requirement of neonates for hospital admission.^53,56,57 Recent reports have shown that the outcomes with multifetal pregnancies have been improved by advances in prenatal care and intensive neonatal care.^54,55

A couple has several options when faced with a multifetal pregnancy.⁵⁸ First, they can electively terminate the multifetal pregnancy with the intent to conceive again. However, because the pregnancy is most likely wanted and achieved at great psychological and economic cost, and because future conceptions are not guaranteed, this option is usually the least desirable. Second, the couple can attempt to proceed with the pregnancy. Even though there are reports of survival of some or all of quadruplets and quintuplets, there is still significant risk of long-term morbidity. Survival with six or seven fetuses, although reported, is extremely rare, and there are no reports of any fetal survivals with eight or more fetuses. Finally, the couple can choose multifetal pregnancy reduction.

Over the past few years, multifetal pregnancy reduction has become a realistic option. Among the different techniques proposed for multifetal reduction, one approach, transabdominal potassium chloride, has been the most widely adopted. This involves an injection through the mother's abdomen into the most easily accessible fetus. The potassium chloride injection produces almost instantaneous death of the injected fetus. The fetal remains gradually degenerate and are often undetectable at delivery. This technique is usually performed at ten to twelve weeks of pregnancy, when the chance of spontaneous loss of the remaining embryos and the risk of complications from a retained nonviable fetus are less likely.⁵⁹

Several recent studies have evaluated the efficacy of transabdominal multifetal pregnancy reduction in improving outcomes.^60-63 Improved outcomes were evident in twins reduced from quadruplets. No such benefit could be found for reduction of triplets to twins in terms of gestational age and mean birth weight, though triplets who were not reduced required a longer stay in the intensive care unit. Furthermore, twins resulting from multifetal reduction were born earlier and weighed less than twins who started out as twins. Thus, the clinical advantage of multifetal reduction for quadruplet pregnancies seems clear, but for triplet gestations, the procedure remains controversial. Twins who are reduced from higher order do not have outcomes as favorable as twins who start out as twins. It is not clear why this should be so; perhaps degenerative products from the retained nonviable fetus somehow cause preterm labor or preterm rupture of membranes. Recent evidence shows that reduced pregnancies have more complications such as placental abruption, preterm labor, and premature rupture of the membranes. The potential for these complications should be discussed with mothers who wish to reduce triplets because the benefits of doing so are not clear.

Obviously, multifetal pregnancy reduction involves complex ethical issues. Abortion is safe, legal, and available to all women, and is not ethically different from multifetal reduction. If multifetal reduction improves the chances of survival of the remaining fetuses, many women may choose this option. Some women will be opposed to the procedure for the same reasons they would be opposed to an abortion, even if the outcomes for the remaining fetuses were improved. Therefore, individual choice will play a large part in making a decision for a reduction. This decision must be based not only on the possible medical benefits of the procedure, but also on the social and practical implications of raising multiple children simultaneously. In the future, with the advent of improved infertility technology, we should see a dramatic reduction in multiple births and, with it, a decreased need for multifetal pregnancy reduction.