Calcium channel blocker does not significantly reduce preterm labor

In women with threatened (symptoms of) preterm labor, maintenance therapy to suppress labor with the calcium-channel blocker nifedipine for 12 days did not result in a significant reduction in adverse perinatal (just before and after birth) outcomes, such as perinatal death, chronic lung disease or neonatal sepsis, when compared with placebo.

Preterm birth is the most common cause of neonatal illness and death worldwide. “Almost 75 percent of perinatal deaths occur in infants born before 37 weeks’ gestation. Consequently, preterm birth is associated with a large burden of disease, high costs for medical care, special education, and institutionalized care for disabled infants. In threatened preterm labor before 34 weeks, delay of delivery for 48 hours allows antenatal corticosteroid treatment to improve fetal maturity and transfer of the pregnant woman to a center with a neonatal intensive care unit,” according to background information in the article. Delay of delivery for more than 48 hours may improve perinatal outcome. “However, the effectiveness of maintenance tocolysis [medication to suppress labor], after an initial course of tocolysis and corticosteroids for 48 hours, on pregnancy and perinatal outcome has not been demonstrated.”

Carolien Roos, M.D., of Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands, and colleagues evaluated the effect of maintenance tocolysis with nifedipine on perinatal outcome. Maintenance tocolysis with nifedipine has been assessed in 3 small trials that showed contradictory results. This randomized controlled trial was conducted in 11 perinatal units including all tertiary centers in the Netherlands. From June 2008 to February 2010, women with threatened preterm labor between 26 weeks and 32 weeks (plus 2 days) gestation, who had not delivered after 48 hours of tocolysis and a completed course of corticosteroids, were enrolled. Surviving infants were followed up until 6 months after birth (ended August 2010).

A total of 406 women were randomly assigned to maintenance tocolysis with nifedipine orally (n = 201) or placebo (n = 205) for 12 days. Average gestational age at randomization was 29.2 weeks for both groups. The primary outcome measure for the study was a composite of adverse perinatal outcomes (perinatal death, chronic lung disease, neonatal sepsis, intraventricular hemorrhage >grade 2, periventricular leukomalacia >grade 1, or necrotizing enterocolitis).

The researchers found that adverse perinatal outcome was not significantly different between the groups, with 24 (11.9 percent) cases in the nifedipine group and 28 (13.7 percent) in the placebo group (risk difference 1.8 percent). Perinatal death occurred in 5 (2.5 percent) in the nifedipine group and in 4 (2.0 percent) in the placebo group. Average gestational age at delivery was comparable for both groups: 34.1 weeks for the nifedipine group and 34.2 weeks for the placebo group.

Birth weight was not significantly different between the 2 groups. Neonatal intensive care unit admission occurred in 40.8 percent of neonates in the nifedipine group and in 39.7 percent in the placebo group. The length of neonatal intensive care unit admission was 10 days for both groups.

“Although the lower than anticipated rate of adverse perinatal outcomes in the control group indicates that a benefit of nifedipine cannot completely be excluded, its use for maintenance tocolysis does not appear beneficial at this time,” the authors write. “Future research should be directed toward therapies tailored to the specific underlying causes of preterm labor.”

Source: Jama Network