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BMI-Specific Gestational Weight Gain Thresholds to Minimize Small Vulnerable Newborn Risk in Underweight Chinese Women

Year: 2025

Type: preprint

Abstract: Background : Maternal underweight elevates small vulnerable newborn (SVN) risk, yet optimal BMI-specific gestational weight gain (GWG) thresholds remain undefined, challenging uniform recommendations for underweight pregnancies. Objective: To quantify how severity of maternal underweight modifies SVN risk, and to determine BMI-specific GWG thresholds that minimize this risk in underweight Chinese women. Methods: In this retrospective cohort study, 23,392 singleton pregnancies with maternal underweight were analyzed from 141,163 deliveries at Guangdong Women and Children Hospital between 1 January 2015 and 30 June 2024. Underweight was graded as Grade 1 (17.5–<18.5 kg/m 2 ), Grade 2 (16–<17.5 kg/m 2 ), or Grade 3 (<16.0 kg/m 2 ). GWG was calculated as weight before delivery minus pre-pregnancy weight. Modified Poisson regression estimated adjusted rate ratios (RRs) for SVN across GWG categories. Restricted cubic splines and two-piecewise models assessed non-linearity and threshold effects. Results: SVN incidence rose dose-dependently with underweight severity: 18.8 % (Grade 1), 23.2 % (Grade 2), and 30.6 % (Grade 3). GWG exhibited a non-linear inverse relationship with SVN risk (P<0.001). Threshold analysis identified BMI-specific optimal GWG: 15.0 kg (Grade 1), 16.3 kg (Grade 2) and 21.5 kg (Grade 3). Two-piece regression revealed each additional kilogram increase in GWG up to these thresholds reduced SVN risk by 8–11 % (RR: 0.89–0.92), further gains above the thresholds conferred no additional benefit. Conclusions: Current uniform recommendation of GWG for underweight women are insufficient for severe underweight. Grade-specific targets particularly 21.5 kg for BMI <16 kg/m 2 are required to minimize SVN risk. Prospective validation and mechanistic studies are warranted to integrate these thresholds into precision prenatal care.

DOI: 10.22541/au.176000615.54538913/v1

Authors: Ziyi Song, Li Zhang, Qing Fang, Jing Peng, Li Wu, Lulu Song, Lijuan Zheng, Guocheng Liu, Gaojie Fan, Surong Mei, Youjie Wang

Institutions: Guangdong Province Women and Children Hospital, Huazhong University of Science and Technology

Language: English

Topic: Gestational Diabetes Research and Management

Subfield: Obstetrics and Gynecology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Funders: National Natural Science Foundation of China, National Key Research and Development Program of China

Awards: G3216124361, G539900409, G6126156645

OpenAlex ID: W4414981578

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