NEW YORK - Women who become pregnant again within 18 months after having a baby are more likely to deliver early, according to a new study.
Past reports have also linked having a short interpregnancy interval with a greater risk of premature birth.
The new study "brings up the importance of adequate birth spacing as a potential modifiable way that women, especially high-risk women, can decrease their chance of having a preterm baby," Emily DeFranco told Reuters Health.
She worked on the study at Cincinnati Children's Hospital Medical Center in Ohio.
"Women who are at the highest risk for preterm birth are those who have had a previous premature birth so (for those women it is) especially important to try to optimize their pregnancy timing," DeFranco said.
The findings suggest a short interpregnancy interval is also linked to the risk of a baby being born a week or two early, though not technically premature. These early term births at 37 and 38 weeks of gestation (full term is 39 to 40 weeks) can have a negative impact on a newborn's health, say the authors.
For their study, DeFranco and her colleagues analyzed information from Ohio birth records from 2006 to 2011. They were able to find the interpregnancy interval for about 450,000 babies born to mothers who had given birth previously.
About 11 per cent of the births occurred after an interpregnancy interval of 12 to 18 months and about 2 per cent followed an interpregnancy interval of less than 12 months.
The researchers found that 53 per cent of women with interpregnancy intervals of less than 12 months gave birth before the 39th week of pregnancy, compared with about 38 per cent of women who had normal interpregnancy intervals of at least 18 months.
Twenty percent of women with the shortest interpregnancy intervals delivered prematurely - before 37 weeks - compared to 10 per cent of women who waited 12 to 18 months between pregnancies and about 8 per centof women with a normal interpregnancy interval.
African American mothers were more likely to have short interpregnancy intervals. They were also more likely to have premature births, even when their pregnancies were at least 18 months apart, according to findings published June 4 online in BJOG: An International Journal of Obstetrics and Gynaecology.