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Interpregnancy interval and hypertensive disorders of pregnancy: A population‐based cohort study
Author(s) -
Gebremedhin Amanuel T.,
Regan Annette K.,
Ball Stephen,
Betrán Ana P.,
Foo Damien,
Gissler Mika,
Håberg Siri E.,
Malacova Eva,
Marinovich Michael Luke,
Pereira Gavin
Publication year - 2021
Publication title -
paediatric and perinatal epidemiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.667
H-Index - 88
eISSN - 1365-3016
pISSN - 0269-5022
DOI - 10.1111/ppe.12668
Subject(s) - medicine , preeclampsia , poisson regression , relative risk , confidence interval , pregnancy , obstetrics , gestational hypertension , population , cohort study , cohort , demography , environmental health , genetics , biology , sociology
Background Despite extensive research on risk factors and mechanisms, the extent to which interpregnancy interval (IPI) affects hypertensive disorders of pregnancy in high‐income countries remains unclear. Objectives To examine the association between IPI and hypertensive disorders of pregnancy in a high‐income country setting using both within‐mother and between‐mother comparisons. Methods A retrospective population‐based cohort study was conducted among 103 909 women who delivered three or more consecutive singleton births (n = 358 046) between 1980 and 2015 in Western Australia. We used conditional Poisson regression with robust variance, matching intervals of the same mother and adjusted for factors that vary within‐mother across pregnancies, to investigate the association between IPI categories (reference 18‐23 months), and the risk of hypertensive disorders of pregnancy. For comparison with previous studies, we also applied unmatched Poisson regression (between‐mother analysis). Results The incidence of preeclampsia and gestational hypertension during the study period was 4%, and 2%, respectively. For the between‐mother comparison, mothers with intervals of 6‐11 months had lower risk of preeclampsia with adjusted relative risk (RR) 0.92 (95% confidence interval [CI] 0.85, 0.98) compared to reference category of 18‐23 months. With the within‐mother matched design, we estimated a larger effect of long IPI on risk of preeclampsia (RR 1.29, 95% CI 1.18, 1.42 for 60‐119 months; and RR 1.30, 95% CI 1.10, 1.53 for intervals ≥120 months) compared to 18‐23 months. Short IPIs were not associated with hypertensive disorders of pregnancy. Conclusions In our cohort, longer IPIs were associated with increased risk of preeclampsia. However, there was insufficient evidence to suggest that short IPIs (<6 months) increase the risks of hypertensive disorders of pregnancy.