Between 1980 and 1998, the number of triplets and higher-order multiples delivered in the United States increased by more than 300 percent. However, since then the rate has stabilized (see Figure 42-1). The increase is attributable to greater use of assisted reproductive technologies. The problems of twin pregnancies are remarkably intensified when there are additional fetuses. The incidence of hypertension, particularly severe preeclampsia, is increased several-fold over that found in twin pregnancies. Improvements in neonatal care have resulted in survival rates as high as 95 percent for liveborn triplets, but prematurity remains a cause of significant morbidity. As the number of fetuses increases, the length of gestation decreases (see Figure 42-2). Routine hospitalization of triplet pregnancies has not been shown to result in neonatal benefits. However, women who develop preterm labor, hypertension, or other pregnancy complications are promptly hospitalized by most clinicians.
FIGURE 42-1 Number of triplet or higher-order multifetal births in the United States, 1980–2005. (Reproduced, with permission, from Cunningham FG, Leveno KJ, Bloom SL, et al (eds). Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010. Data from Martin JA, Park MM: Trends in twin and triplet births: 1980–97. Natl Vital Stat Rep 47:1, 1999; Martin JA, Hamilton BE, Sutton PD, et al: Births: Final data for 2005. Nat Vital Stat Rep 56:1, 2007.)
FIGURE 42-2 Cumulative percent of singleton, twin, and triplet or higher-order multi-fetal births according to gestational age at delivery in the United States during 1990. (Redrawn, with permission, from Luke B: The changing pattern of multiple births in the United States: Maternal and infant characteristics 1973 and 1990. Obstet Gynecol 84(1):101–106, 1994.)
Delivery of pregnancies with three or more fetuses can be significantly more complicated than delivery of twins. For a variety of reasons, women with triplets or more often undergo cesarean delivery.
For further reading in Williams Obstetrics, 23rd ed.,
see Chapter 39, “Multifetal Gestation.”