Spans between pregnancies studied

Women who become pregnant less than 18 months after giving birth face a higher risk of having a small, premature or low-birth-weight baby, according to a new study.

The report, published in today’s Journal of the American Medical Association, also found that spacing pregnancies more than five years apart brought a higher risk of complications.

The study provided the most comprehensive look at the issue of spacing between pregnancies, which over the years has produced myriad recommendations.

“Before we could talk about the importance of good spacing, but we couldn’t talk about what it means,” said Dr. Nancy Green, medical director of the March of Dimes. “Now the advice we give to a woman is very clear.”

Dr. Agustin Conde-Agudelo of Santa Fe de Bogota Foundation in Colombia, who led the study, said the findings could prevent thousands of annual infant deaths.

Premature infants have a greater risk of dying or suffering developmental deficits. Low-birth-weight babies – those under 5.5 pounds – and babies born small for their gestational age also face greater risks.

“The new evidence presented in our study makes child spacing compelling as a health issue of global importance,” he said.

The research analyzed data from 67 studies conducted in the U.S., Europe and underdeveloped nations during the last 30 years.

Conde-Agudelo said the data was adjusted for socioeconomic conditions and other factors, therefore “the findings can be applied to both developed and developing countries.”

A separate analysis of U.S.-based studies produced similar results, he said.

The report found that women who became pregnant less than 18 months after giving birth increased their risk of having a premature infant by about 2 percent for every month short of 18 months. The risk of having a low-birth-weight infant was increased by 3 percent each month. The risk of having infants small for their gestational age was 0.5 percent higher for every month.

Conde-Agudelo said a possible explanation for the problems is that pregnancies in close succession probably deplete the mother’s nutritional stores.

For women who became pregnant after five years, the risk of complications increased by less than 1 percent a month.

Conde-Agudelo said it was less clear why long periods between pregnancies were associated with more complications. Researchers said it was possible that mothers in this group were older or had more health problems that might have affected their pregnancies.

The highest risks found by the study were for pregnancies separated by less than six months, which were associated with a significantly higher risk of complications and a higher rate of infant mortality and stillborn births.

Dr. Mark A. Klebanoff, director of the National Institute of Child Health and Human Development, said he believed the study overstated the risks.

Klebanoff, who studied birth spacing in the 1980s, said the impact of spacing is influenced by many factors.

The study’s data, he said, was not detailed enough to adjust for all the possible conditions. He noted, for example, that the study did not separate out women who had a history of problem pregnancies.