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Multiple Gestation

Multiple gestation occurs in about 1.5% of all births. Although multiple pregnancies of higher order (greater than three) presently constitute a relatively small component of the total, these numbers are increasing as a result of the widespread use of assisted reproductive technologies twins.

Twins may result either from the splitting of a single fertilized ovum into two genetically identical individuals (monozygotic) or when two separate ova are each fertilized by a sperm, leading to genetically distinct siblings (dizygotic). Although the incidence of monozygotic twinning is fairly constant throughout the world at a rate of approximately 1 per 250 births.

Multiple gestation should be suspected when there is a history of use of a fertility agent, a discrepancy between the estimated gestational age and uterine size, or abnormally elevated laboratory screening tests such as maternal serum alpha-fetoprotein or triple screens. A careful ultrasound examination will not only confirm the diagnosis, but also should determine zygosity.

Perinatal morbidity and mortality increase in direct proportion to fetal number. Complications related to preterm birth, such as respiratory distress syndrome, intracerebral hemorrhage, sepsis, and necrotizing enterocolitis, account for most of these adverse outcomes. Congenital malformations, fetal growth restriction, and umbilical cord prolapse also occur more frequently.

Multiple gestations increase the maternal risk of hyperemesis gravidarum, spontaneous abortion, PIH, anemia, abnormal placentation, hydramnios, PROM, and postpartum hemorrhage. There is also an increased risk of operative delivery.


Antenatal management should include attention to adequate nutrition, avoidance of strenuous physical activity, frequent prenatal visits, and counseling on symptoms of preterm labor, PROM, and hypertensive disorders of pregnancy. Ultrasound assessment of fetal growth and amniotic fluid volume should be performed every 4 weeks unless evidence of an abnormality suggests that this be done more frequently. Discordant fetal growth may be due to constitutional differences in otherwise normal twins, growth restriction of one fetus, a chromosomal or anatomic abnormality of one fetus, or the twin-twin transfusion syndrome.

The choice of route of delivery depends on the presentation at the time labor occurs. Vaginal delivery is the preferred approach when both twins are in a vertex presentation. After delivery of twin A, and with continuous surveillance of twin B with real-time ultrasonography or electronic monitoring, it is believed that the interval between delivery of the twins.

Embryo Reduction

The higher-order multiple gestations resulting from assisted reproductive technologies have many associated problems. Of greatest significance to the offspring is the increased risk of preterm delivery, which is directly proportional to the number of fetuses developing in utero. Multifetal pregnancy reduction is a procedure designed to increase the chances of delivering closer to term.

Originally, multifetal pregnancy reduction was accomplished by transcervical suction curettage. This approach was soon abandoned, and the procedure is now usually performed via the transabdominal or transvaginal route.

The incidence of preterm delivery increases with increasing numbers of fetuses; the mean gestational age of delivery for singletons, twins, triplets, and quadruplets is 39, 35, 33, and 31 weeks, respectively. Multifetal pregnancy reduction increases gestational age.

The data regarding triplets, however, are not as definitive. Some studies have suggested that multifetal pregnancy reduction reduces the spontaneous loss rate in these gestations, and the rates of intraventricular hemorrhage and respiratory distress syndrome.

In contrast to multifetal pregnancy reduction, selective termination is performed on a specific fetus known to be anomalous as a result of karyotype analysis or ultrasound detection. Whereas multifetal pregnancy reduction is almost always performed.

Several international collaborative studies of multifetal pregnancy reduction and selective termination procedures have been published. Initially, the reported rates of loss of the remaining fetus after transabdominal and transvaginal multifetal pregnancy reduction procedures performed before 24 weeks of gestation were 16.2% and 13.1%, respectively. At these experienced centers, however, this rate decreased to 8.8% for transabdominal cases; follow-up on transvaginal cases has yet to be published.

The antenatal care of post-multifetal pregnancy reduction twins is no different from that of spontaneous twins, except for one screening tool. Maternal serum alpha-feto-protein levels after a reduction are consistently higher than those for nonreduced twins at comparable ages because of the retained dead fetus(es). Therefore, maternal serum alpha-fetoprotein cannot be used to screen.

Multifetal pregnancy reduction optimizes the chances of a woman successfully maintaining her pregnancy by decreasing the risks of preterm delivery. For many women, this is not a light decision. Multifetal pregnancy reduction is associated with mourning for the lost fetus(es), guilt, and sadness, but overall, it is well tolerated.