Maternal alcohol use during pregnancy contributes to substantial increase in risk for extreme preterm delivery

May 28 2007

Preterm delivery, and particularly "extreme prematurity", defined as less than 32 weeks of gestation, are major contributors to perinatal sickness and death worldwide.

A new study has found that maternal alcohol use during pregnancy can contribute to a substantial increase in risk for extreme preterm delivery.

Results are published in the June issue of Alcoholism: Clinical & Experimental Research .

"Preterm birth has increased in part because of assisted reproductive technology and indicated medical intervention, however, we believed that we could also detect the impact of alcohol," said Robert J. Sokol, distinguished professor of obstetrics and gynecology and Director of the C.S. Mott Center for Human Growth and Development at Wayne State University. "In most previous studies, pregnancy dating was much less certain; but we used ultrasound dating. It's like listening to FM radio, rather than AM radio that has a lot of static; it is easier to hear what's being said with less noise in the background."

Sokol and his colleagues collected data on exposure to alcohol, cocaine and cigarettes, as well as corresponding outcomes, from 3,130 pregnant women and their infants. As noted above, the researchers also used ultrasound to provide specific pregnancy dating. Of the newborns, 66 were extremely preterm, 462 were mildly preterm, and 2,602 were term deliveries.

Findings indicated that alcohol and cocaine, but not cigarette, use were associated with an increased risk of extreme preterm delivery; alcohol accounted for the lion's share of the risk. Furthermore, the effects were greater in pregnancies among women older than 30 years of age.

"Although we found smoking to be associated with mild preterm, but not extreme preterm, delivery," said Sokol, "smoking remains a recognized risk for preterm delivery and should still be considered a problem from the fetal perspective."

Although there is less clarity on why the effects of alcohol on prematurity were more pronounced among women aged 30 years and older, Sokol said he and other researchers have seen what appears to be a greater susceptibility to neurobehavioral effects and anatomic congenital anomalies in pregnancies among older women. "This is an important finding," he said, "because a woman could have been drinking during pregnancy when she was younger and had no effects, but could be more susceptible later."

Given that the patient population was 92 percent African American, added Sokol, the results will need to be confirmed elsewhere, using similar methodology. "The baseline risk for preterm delivery is higher among African Americans than whites in the United states," he said. "There are known ethnicity effects for prenatal alcohol exposure, so studying pregnancies among whites would be sensible, yet if I had to guess, I think we would see changes in the same direction."

The bottom line, said Sokol, is that there is a substantial risk of extreme preterm delivery that is associated with alcohol use during pregnancy. "It would be best for women to just not drink during pregnancy," he said.