Thesis (Ph.D.)--Boston UniversityPreeclampsia is associated with disproportionately high rates of neonatal mortality and morbidity. Both therapeutic and prophylactic interventions have been lacking and delivery of the placenta remains the only effective cure for this obstetrical complication.
In study 1 we examined the association between prior induced abortion and preeclampsia among nulliparous women in the Medical Birth Register (MBR) of Finland from 1996-2010. Preeclampsia cases (n=12,650) and frequency matched controls (n=50,600) were linked with the Finnish Registry of Induced Abortions to collect data on any prior induced abortions (IA), method of IA, and gestational age at the time of IA. History ofiA was associated with a decreased risk ofpreeclampsia (OR 0.89, 95% CI 0.84, 0.95). The risk of preeclampsia decreased further with an increasing number of prior IA with decreased risks of 8%, 23%, and 26% for 1, 2, and 2:3 lAs, respectively.
These associations become more protective after restricting the analysis to women with no history of spontaneous abmtion (SAB). Surgical abortions at 2:12 weeks were associated with the greatest reduction in risk of preeclampsia (OR 0.81 95% CI 0.61,
1.06). Our study confirms previous findings of a protective effect of IA on risk of preeclampsia and provides new information regarding method and gestational age of abortion in relation to preeclampsia risk.
In study 2 we investigated the potential for a differential effect of placental abruption on preeclampsia, based on the gestational age at the time of abruption among parous women in the MBR of Finland from 1996-2010. Cases of preeclampsia (n=6,487) and frequency matched controls (n=25,948) were linked to the Hospital Discharge Registry (HDR) and MBR to ascertain data on prior placental abruption. Placental abruption was categorized as preterm (<37 weeks) or term (2:37 weeks). Preterm abruptions were associated with a two-fold increase in risk of preeclampsia (OR 2.18 95% CI 1.45, 3.30). In contrast term placental abruption was not associated with preeclampsia. The association between preterm placental abruption and preeclampsia was further elevated among women with a history of preeclampsia. Associations with preterm abruption were also strengthened when the outcome was defined as early-onset preeclampsia (<34 weeks). Placental abruption in a prior pregnancy conferred a different risk of preeclampsia based on the gestational age of the abruption affected pregnancy.
Lastly, in study 3 we examined the association between intrauterine device (IUD) use and preeclampsia among women in the United Kingdom's Clinical Practice Research Database from 1993-2010. Data on IUD use was obtained from patient records for 2,837 cases and 11 ,221 matched controls. Any prior IUD use was associated with a reduced risk of preeclampsia (OR 0.77 95% CI 0.61 , 0.98). Timing of removal in relation to the start of pregnancy showed an inverse association, with shorter intervals associated with the largest decreases in risk of preeclampsia. IUD removal within a year prior to pregnancy had an OR of 0.66 (95% CI 0.46, 0.96). Associations were most notable for women with a BMI <25kg/m and for women with no prior births. IUD use prior to pregnancy was associated with a reduced risk of preeclampsia, which was most apparent for those using an IUD within a year prior to pregnancy
