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Original Article
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Volume 346:33-38 January 3, 2002 Number 1
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The Interval between Pregnancies and the Risk of Preeclampsia
Rolv Skjærven, Ph.D., Allen J. Wilcox, M.D., Ph.D., and Rolv T. Lie, Ph.D.

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ABSTRACT

Background The risk of preeclampsia is generally lower in second pregnancies than in first pregnancies, but not if the mother has a new partner for the second pregnancy. One explanation is that the risk is reduced with repeated maternal exposure and adaptation to specific antigens from the same partner. However, the difference in risk might instead be explained by the interval between births. A longer interbirth interval may be associated with both a change of partner and a higher risk of preeclampsia.

Methods We used data from the Medical Birth Registry of Norway, a population-based registry that includes births that occurred between 1967 and 1998. We studied 551,478 women who had two or more singleton deliveries and 209,423 women who had three or more singleton deliveries.

Results Preeclampsia occurred during 3.9 percent of first pregnancies, 1.7 percent of second pregnancies, and 1.8 percent of third pregnancies when the woman had the same partner. 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, the risk approximated that among nulliparous women. After adjustment for the presence or absence of a change of partner, maternal age, and year of delivery, the odds ratio for preeclampsia for each one-year increase in the interbirth interval was 1.12 (95 percent confidence interval, 1.11 to 1.13). In unadjusted analyses, a pregnancy involving a new partner was associated with higher risk of preeclampsia, but after adjustment for the interbirth interval, the risk of preeclampsia was reduced (odds ratio for preeclampsia with a change of partner, 0.73; 95 percent confidence interval, 0.66 to 0.81).

Conclusions The protective effect of previous pregnancy against preeclampsia is transient. After adjustment for the interval between births, a change of partner is not associated with an increased risk of preeclampsia.


Source Information

From the Section for Medical Statistics, Department of Public Health and Primary Health Care, and the Medical Birth Registry of Norway, Locus for Registry-Based Epidemiology, University of Bergen, Bergen, Norway (R.S., R.T.L.); and the Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, N.C. (A.J.W.).

Address reprint requests to Professor Skjærven at the Section for Medical Statistics, University of Bergen, Armauer Hansens Bldg., 5021 Bergen, Norway, or at rolv.skjaerven{at}smis.uib.no.

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Related Letters:

The Interval between Pregnancies and Preeclampsia
Saftlas A. F., Levine R. J., Skjærven R., Wilcox A. J., Lie R. T.
Extract | Full Text | PDF  
N Engl J Med 2002; 346:1831-1832, Jun 6, 2002. Correspondence

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