Women who are pregnant with more than one child, compared with those expecting one child, are 2-4 times as likely to experience complications of childbirth, according to an analysis of data on 885,338 pregnant women in Latin America and the Caribbean.¹ For example, women who are pregnant with more than one child are three times as likely as women pregnant with one child to have eclampsia or to need a cesarean delivery and are four times as likely to experience preterm labor. Among women who have given birth before, those who are pregnant with more than one child are twice as likely to die as women pregnant with one child. In addition, women who are carrying more than one child and have never given birth before are 2-7 times as likely as those who have given birth before to experience certain adverse maternal outcomes.

To investigate whether women pregnant with more than one child have a higher risk of adverse maternal outcomes than women with singleton gestations, researchers collected data from the Perinatal Information System in Montevideo, Uruguay. Between 1985 and 1997, hospitals entered into the database more than one million perinatal clinical records on pregnancies of women from Argentina, Bahamas, Bolivia, Brazil, Chile, Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Uruguay and Venezuela. The records include demographic information, reproductive history, maternal characteristics and data on prenatal care, labor management, maternal complications and neonatal outcomes. While the records do not include information on the use of assisted reproductive technologies, the multiple gestations that occurred are likely to have occurred naturally because the availability of these technologies was limited in developing countries when the research was conducted.

The researchers excluded 12% of the records in the database from their analysis because information was missing or implausible, leaving a final sample of 885,338 pregnancies. Of these, 15,484 (approximately 2%) were multiple gestations--pregnancies involving more than one fetus. The researchers estimated the relative risks of adverse maternal outcomes associated with multiple gestation and adjusted these estimates for maternal age, number of previous births, education, smoking, height, prepregnancy weight and body mass index, history of high blood pressure, the trimester in which the mother began prenatal care, the number of prenatal care visits, geographic area, hospital type and year of delivery.

Multiple gestations were more common among women who were older, had given birth before, had a higher body mass index prior to pregnancy and had a family history of multiple gestations. For example, women who were at least 35 years old were more than three times as likely to be pregnant with more than one child than women who were younger than 20, and women who had a family history of multiple gestations were three times as likely as women who did not to have multiple gestations. There was no association between multiple gestations and history of abortion.

After adjusting the data for confounding variables, the researchers found that several adverse outcomes were significantly more common among women with multiple gestations. Women pregnant with more than one child were four times as likely as women pregnant with one child to experience preterm labor, three times as likely to experience eclampsia and cesarean delivery, and twice as likely to experience preeclampsia, anemia, postpartum hemorrhage and postpartum infection.

The researchers also calculated the estimated risk of complications associated with multiple gestations for women who had never given birth before and for women who had previously given birth. Among women having their first birth, those with multiple gestations were seven times as likely as those with singleton gestations to have a preterm delivery, six times as likely to experience eclampsia and three times as likely to have a cesarean delivery. Parous women who were pregnant with more than one child were twice as likely to die and to have a cesarean delivery and were three times as likely to experience preterm labor as parous women pregnant with only one child.

For most of the adverse outcomes in the researchers' analysis, whether a woman had given birth before did not make a difference in the elevated risk associated with multiple gestations. However, for eclampsia, preterm labor and cesarean delivery, the elevated risk associated with multiple gestation was significantly higher for women having their first birth than for those who had given birth at least once.

The researchers note that the accuracy of diagnoses in the database has not been verified and that complications could be underreported. However, because the rates of complications in their study are similar to those reported in other studies, they believe that this potential limitation is not likely to have affected their findings. They conclude that multiple gestations should be included among risk factors for maternal mortality and that there be programs specifically designed for women carrying multiple gestations. Furthermore, they say that their findings, in addition to the "well-known increased risk of neonatal morbidity and mortality among multiple gestations, should focus attention on indiscriminate use of ovulation-inducing agents and assisted-reproductive technologies that raise the rate of multiple gestations."--B. Brown

REFERENCE

1. Conde-Agudelo A, Belizan JM and Lindmark G, Maternal morbidity and mortality associated with multiple gestations, Obstetrics and Gynecology, 2000, 95(6):899-903.