Development and evaluation of percentile distribution of body weight by gestational week as a tool for gestational weight management: a retrospective study based on hospital routine data

Objectives: This study aimed to construct and validate smoothed gestational weight centile curves based on preconception weight status for Chinese pregnant women.

Design: A retrospective study based on hospital routine data SETTING: Hospital prenatal care.

Population: A cohort of pregnant Chinese women with preconception and gestational body weights without maternal or neonatal complications (sample 1, n=2992), and a non-selective independent sample (sample 2, n=7420), were selected from hospital routine data for curve construction and validation.

Study design: Smoothed body weight centile curves for each gestational week were constructed using the LMS method in sample 1. Validation in sample 2 included analysis of agreement between predicted weight at the 38th week and observed values using the Bland-Altman Index. Predictions were also compared with international curves.

Results: Smoothed centile curves of gestational weight for the three preconception body mass index groups showed a similar non-linear increasing trend. The differences between predicted body weights and observed values were 0.66±1.58 kg, 0.14±1.61 kg and -0.54±2.06 kg in the underweight, normal weight and overweight groups, respectively. Bland-Altman Index values were 5.2%, 5.6% and 4.7% in the underweight, normal weight and overweight groups, respectively, with limits of agreement of -2.4~3.8 kg, -3.0~3.3 kg and -4.4~3.4 kg, respectively. These limits of agreement were narrower than those of available international curves.

Conclusion: Body weight percentiles for gestational weeks 0-42 were proposed for underweight, normal weight or overweight Chinese women. These curves could constitute a useful tool for individualised gestational weight management by predicting body weight at a later gestation phase.