ABSTRACT Although it has been observed that the incidence of preeclampsia is lower among women having their second pregnancy than among women having their first, it is unclear whether protection against preeclampsia results from parity or gravidity. For example, 1 previous study reported a protective effect in the second pregnancy of a late miscarriage in the first pregnancy, whereas other studies have found that only deliveries >37 completed weeks have a protective effect. Another study showed that a previous abortion, either spontaneous or therapeutic, was protective, irrespective of gestational age. This retrospective observational study was designed to determine whether the reduced risk of preeclampsia in the second pregnancy is dependent or independent of the first pregnancy's outcome, including the gestational age at delivery. Data from 24,500 women with first and second pregnancies between 1986 and 2006 were obtained from the Aberdeen Maternity and Neonatal Databank in Scotland. The treatment group included all women who developed preeclampsia in their second pregnancy, whereas the control group included all women with normotensive second pregnancies. Potential independent risk factors for the development of preeclampsia in the second pregnancy were evaluated, and crude and adjusted odds ratios (OR) were estimated using binary logistic regression. A total of 903 (3.7%) of the 24,500 women in the study population had preeclampsia in the second pregnancy. Of these, 167 had a previous history of preeclampsia, for a recurrence rate of 14.2%. The incidence of preeclampsia was increased in women with interpregnancy intervals of 6 years or more (19.3% vs. 14.7%) and in those with an increase in BMI (70.8% vs. 63.2%), whereas a change of partner appeared to have a protective effect (3.5% vs. 5.6%). Compared to women who were normotensive in the first pregnancy, women with a history of preeclampsia in the previous pregnancy had an adjusted odds ratio of 5.12 (95% confidence interval [CI] of 4.42–6.48) for developing preeclampsia in the second pregnancy. Using a model that included only live births, and after controlling for maternal age, BMI, smoking, change of partner, interpregnancy interval, and previous history of preeclampsia or gestational hypertension, the risk of preeclampsia in the second pregnancy appeared to decrease with increasing gestational age at delivery of the first pregnancy. Compared to women who had a previous term delivery, the odds ratio for developing preeclampsia in the second pregnancy was 4.22 (95% CI, 2.54–7.03) for women whose previous pregnancy ended in the second trimester, 2.32 (95% CI, 1.62–3.32) for women who had a previous preterm birth at 25 to 32 weeks', and 1.62 (95% CI, 1.46–1.72) for those with a previous preterm birth at 33 to 36 weeks'. The effect of a previous fetal death was evaluated using a second model that included all study patients whose previous pregnancy extended beyond 20 weeks. After adjusting for the same variables listed above, the risk of preeclampsia was the same for women with a previous history of stillbirth as for those with a previous live birth. Only first deliveries beyond 37 weeks were protective against preeclampsia, independent of outcome, in the second pregnancy. These findings suggest that the protective effect of a previous pregnancy against preeclampsia in the second pregnancy is dependent on the gestational age at delivery of the first pregnancy but not on that pregnancy's outcome.