A prospective population-based multicentre study on the impact of maternal body mass index on adverse pregnancy outcomes: Focus on normal weight

Fieke van Hoorn*, Leon de Wit, Lenie van Rossem, Marielle Jambroes, Floris Groenendaal, Anneke Kwee, Marije Lamain de Ruiter, Arie Franx, Bas B. van Rijn, Maria P.H. Koster, Mireille N. Bekker

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Background Maternal body mass index (BMI) below or above the reference interval (18.5-24.9 kg/m2) is associated with adverse pregnancy outcomes. Whether BMI exerts an effect within the reference interval is unclear. Therefore, we assessed the association between adverse pregnancy outcomes and BMI, in particular within the reference interval, in a general unselected pregnant population. Methods Data was extracted from a prospective population-based multicentre cohort (Risk Estimation for PrEgnancy Complications to provide Tailored care (RESPECT) study) conducted between December 2012 to January 2014. BMI was studied in categories (I: <18.5, II: 18.5-19.9, III: 20.0-22.9, IV: 23.0-24.9, V: 25.0-27.4, VI: 27.5-29.9, VII: >30.0 kg/m2) and as a continuous variable within the reference interval. Adverse pregnancy outcomes were defined as composite endpoints for maternal, neonatal or any pregnancy complication, and for adverse pregnancy outcomes individually. Linear trends were assessed using linear-by-linear association analysis and (adjusted) relative risks by regression analysis. Results The median BMI of the 3671 included women was 23.2 kg/m2 (IQR 21.1-26.2). Adverse pregnancy outcomes were reported in 1256 (34.2%). Linear associations were observed between BMI categories and all three composite endpoints, and individually for pregnancy-induced hypertension (PIH), preeclampsia, gestational diabetes mellitus (GDM), large-for-gestational-age (LGA) neonates; but not for small-for-gestational-age neonates and preterm birth. Within the reference interval, BMI was associated with the composite maternal endpoint, PIH, GDM and LGA, with adjusted relative risks of 1.15 (95%CI 1.06-1.26), 1.12 (95%CI 1.00-1.26), 1.31 (95%CI 1.11-1.55) and 1.09 (95%CI 1.01-1.17). Conclusions Graded increase in maternal BMI appears to be an indicator of risk for adverse pregnancy outcomes even among women with a BMI within the reference interval. The extent to which BMI directly contributes to the increased risk in this group should be evaluated in order to determine strategies most valuable for promoting safety and long-term health for mothers and their offspring.

Original languageEnglish
Article numbere0257722
JournalPLoS ONE
Issue number9 September
Publication statusPublished - 23 Sept 2021

Bibliographical note

Funding Information:
The RESPECT study was conducted with the support of the Netherlands Organization for Health Research and Development (ZonMw; https://www.zonmw.nl/en/; project no 209020004). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
© 2021 van Hoorn et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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