Higher risk of pre-eclampsia after change of partner. An effect of longer interpregnancy intervals?

Epidemiologic studies have shown that pre-eclampsia is mainly a disease of first pregnancy, possibly associated with primipaternity. The inter-pregnancy interval, which is strongly associated with change of partner, has received little attention. In this study, based on Danish hospital records, we evaluated whether the interpregnancy interval may confound or modify the paternal effect on pre-eclampsia. We studied the outcome of the second birth in a cohort of Danish women with preeclampsia in the previous birth (8,401 women) and in all women with pre-eclampsia in second (but not first) birth together with a sample of women with two births (26,596 women). A long interpregnancy interval was associated with a higher risk of pre-eclampsia in women with no previous preeclampsia when the father was the same. We estimated the risk of pre-eclampsia in second birth according to paternal change in different models. Although partner change was associated with an increased risk of pre-eclampsia in women with no history of pre-eclampsia, this effect disappeared after adjustment for the interpregnancy interval. We saw, however, different results when we stratified on the length of the interval. Our results indicate that the interval between births should be taken into consideration when studying the effect of changing partner on pre,eclampsia.