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Int J Epidemiol. 2008 Dec;37(6):1333-40. doi: 10.1093/ije/dyn167. Epub 2008 Oct 21.

Previous abortions and risk of pre-eclampsia.

Author information

1
Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. lill.trogstad@fhi.no

Abstract

BACKGROUND:

The risk of pre-eclampsia is reduced for second and later births. The causes and mechanisms behind this reduction are unknown. The aim of the study was to estimate the risk of pre-eclampsia in primiparous women according to history of spontaneous and induced abortions, while controlling for several potentially confounding factors.

METHODS:

The sample consisted of 20 846 primiparous women participating in the Norwegian Mother and Child Cohort Study (MoBa). Information on abortions and confounders were self-reported in postal questionnaires. The diagnosis of pre-eclampsia was retrieved from the Medical Birth Registry of Norway. Estimation and confounder control was performed with multiple, logistic regression.

RESULTS:

One previous induced abortion reduced the risk moderately [odds ratio (OR) 0.84, 95% confidence interval (CI) 0.69-1.02]. Two or more induced abortions reduced the risk more significantly (OR 0.36, 95% CI 0.18-0.73). Adjustment for confounders did not change the estimates.

CONCLUSIONS:

The protective effect of two prior induced abortions was similar to what is commonly seen after one birth. Spontaneous abortions may to a larger extent than induced abortions be associated with other factors, such as infertility, that may increase the risk of pre-eclampsia. Normal pregnancies interrupted in early pregnancy may induce immunological changes that reduce the risk of pre-eclampsia in a subsequent pregnancy.

PMID:
18940837
PMCID:
PMC2734071
DOI:
10.1093/ije/dyn167
[Indexed for MEDLINE]
Free PMC Article

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