Multiple Pregnancy Prevention

A. Multiple Pregnancy

Although human pituitary gonadotropin and other ovulation induction agents result in fewer multiple pregnancies when used by experts, even in the best of hands it is inevitable that some multiple pregnancies will occur. For example, clomiphene citrate induction of multiple ovulation increases the rate of dizygotic pregnancy to 5-10%.

With many forms of assisted reproductive technology (eg, ovulation induction, in vitro fertilization), iatrogenic multiple pregnancies regularly occur in which the number of fetuses is so great that they may preclude any being carried to the point of viability. When this occurs, many authorities recommend multifetal pregnancy reduction by transabdominal intracardiac potassium injection.

B. Complications of Multiple Pregnancy

To prevent the complications of multiple pregnancy, it is imperative to make the diagnosis as early in pregnancy as possible. Fortunately, ultrasonography can be safely used at any time during pregnancy, is highly accurate, and may be used as early as the fourth week. Later in pregnancy, ultrasonography is useful to monitor the growth of the fetuses and to detect gross anomalies. It is recommended to perform routine growth scans on twins every 4 weeks in the third trimester, or more frequently if growth restriction is detected. Recall that the risk of fetal abnormality in twins is approximately 3 times that in singleton pregnancy.

There is little question that enhancing antenatal care assists in improving outcome. The most commonly used techniques are iron supplementation, vitamin and folic acid administration (in an attempt to avoid anemia), a high-protein diet, and more weight gain than usual (ideal weight for height plus 35-45 lb). There is not enough evidence to suggest a policy of routine hospitalization for bed rest in multiple pregnancy because no reduction in the risk of preterm birth or perinatal death is evident. There is also no evidence that prophylactic cerclage improves outcome. More frequent antenatal visits are scheduled and several authorities recommend closely following cervical length by ultrasound. Emergency cerclage can be offered for a short cervix or a large funnel of membranes prior to 24 weeks. Early and prompt therapy for any complications (eg, vaginal infections, preeclampsia-eclampsia) should be instituted.

Tocolytic drugs may suppress premature labor and extend gestation 48 hours so that the effects of steroids may be realized. There is no evidence that long-term oral or intravenous tocolysis improves outcome. Most authorities recommend starting with intravenous magnesium sulfate. If terbutaline is used, very close monitoring for pulmonary edema must be maintained, because this complication is much more likely with administration of beta-mimetic agents in multiple gestation. Also, remember that indomethacin may influence fetal ductal constriction and should not be used after 32 weeks' gestation.