Women whose water has broken early may want to wait at least 18 months before having their next child, new research shows.

Known by doctors as preterm premature rupture of membranes, this complication, in which a woman’s water breaks before her pregnancy has reached full term and before labor has begun, occurs in up to 5 percent of pregnancies, Dr. Darios Getahun of Kaiser Permanente Southern California Medical Group in Pasadena and colleagues note in their report.

The complication accounts for one in every four premature births, they report in the American Journal of Obstetrics & Gynecology, and puts mother and fetus at risk of infection.

While the reasons why some women’s water breaks early are “elusive,” Getahun and his team say, there are likely many factors involved. Women who have had the complication previously, they add, are known to be at greater risk in subsequent pregnancies. And the risk is also known to be higher for black women compared to whites.

To investigate whether the length of time between pregnancies might also influence this risk, the researchers reviewed data from the state of Missouri on nearly 200,000 women who had two or three children between 1989 and 1997. Around 3 percent of black women and 1 percent of white women’s water broke early during their first or second pregnancies.

Among white women whose water broke early, 6 percent had the complication in their subsequent pregnancy, compared to 2 percent of women who hadn’t suffered premature membrane rupture.

The rates for black women were 10 percent and 4 percent, respectively. This translated to a nearly nine-fold increased risk of subsequent early water breaking for white women, and a seven-fold greater risk for black women.

The risk was even further increased if a woman got pregnant again within 18 months, and was particularly high for African-American women. For example, a black woman who got pregnant again within three to six months would be nearly nine times more likely to have the complication than a woman who waited at least 18 months.

The risk of early water breaking for white women who got pregnant again this soon was tripled.

This suggests, the researchers say, that the complication may be related to inflammation, and that a longer interval between pregnancies is needed to allow for full recovery. “We think that it might be a chronic inflammation that may persist from one pregnancy to another pregnancy,” Getahun told Reuters Health.

Women whose water has broken early should be watched closely in subsequent pregnancies, he added, so that if infection does develop they can receive prompt antibiotic treatment, which could help prevent the complication from recurring.

SOURCE: American Journal of Obstetrics & Gynecology, online February 4, 2010.