Birth interval and pre-eclampsia

A longer birth interval between pregnancies appears to be a major risk factor for pre-eclampsia. It is a complication of pregnancy, which occurs in approximately 5% of all pregnancies. If left untreated, pre-eclampsia can develop into eclampsia, a life-threatening condition in which a woman has convulsive seizures in late pregnancy or during the first week after delivery. Women who experience a dangerous rise in blood pressure during pregnancy have a lower risk of the condition in subsequent pregnancies. But according to new findings, waiting 10 years or more between births may increase this risk. The study was carried out at the University of Bergen in Norway. The investigators reviewed more than 760,000 women who had delivered at least two babies in Norway between 1967 and 1998. Pre-eclampsia occurred in nearly 4% of first pregnancies, 1.7% of all second pregnancies and 1.8% of third pregnancies, when the woman had the same partner. The risk of pre-eclampsia is generally lower in second pregnancies than in first pregnancies. The risk in a second or third pregnancy was directly related to the time that had elapsed since the preceding delivery, and when the interbirth interval was 10 years or more. Similarly, the risk rose between the second and third pregnancies among women who waited the longest to give birth again. Among women with the same partner, most had a second baby within 3 years, compared with 6 years among women who changed partners. Women who bear children with the same man are thought to adapt to his genetic material, thereby reducing the risk of pre-eclampsia, a condition whose exact cause is not known. The protective effect of previous pregnancy for pre-eclampsia is transient. A longer interbirth interval may be associated with a higher risk of pre-eclampsia.

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