title: Partner change, birth interval and risk of pre-eclampsia: a paradoxical triangle.
abstract: Immunology has been hypothesised to play a critical role in the development of pre-eclampsia. A number of epidemiological studies have shown that multiparous women who changed partner had an increased risk of pre-eclampsia in the following pregnancy compared with multiparous women with the same partner. However, partner change is often associated with a long birth interval. Two recent papers using data from the same birth registry reported that, after controlling for birth interval, partner change was associated with a reduced risk of pre-eclampsia. Based on a causal diagram, the author argues conceptually that birth interval is not a confounder but more likely to be a collider. Controlling for or stratifying birth interval in the association between partner change and risk of pre-eclampsia could be inappropriate and may have produced a spurious association.
authors.affiliation: Epidemiology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. zhangj@mail.nih.gov
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D001721:Birth Intervals; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D010298:Parity; D011225:Pre-Eclampsia / Q000453:epidemiology / Q000209:etiology*; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012307:Risk Factors; D012747:Sexual Partners