A longitudinal study of weight gain in pregnancy in Malawi: unconditional and conditional standards.
BACKGROUND
To monitor weight gain during pregnancy and assess its relation with perinatal health outcomes, both unconditional (cross-sectional) and conditional (longitudinal) standards of maternal weight are needed.


OBJECTIVE
This study aimed to develop and validate unconditional and conditional maternal weight standards for use in Malawi, Africa.


METHODS
Longitudinal data were drawn from an antenatal care intervention study conducted in Malawi. Participants were selected for this analysis if they had a healthy profile defined by body mass index and infectious disease measures and delivered healthy singletons defined by birth weight, gestational age, and neonatal survival status. A total of 1733 measurements from 358 women were randomly split to form development and validation samples.


RESULTS
Unconditional and conditional standards were developed and validated. An electronic spreadsheet implements the calculations. Weight gain during pregnancy was substantially slower in this cohort than the US Institute of Medicine recommendation. The percentiles increased linearly; therefore, the use of the conditional standards is robust to inaccuracy in gestational age estimates.


CONCLUSIONS
The standards can facilitate researchers and clinicians to examine maternal weight and weight gain and estimate their associations with pregnancy outcomes in Malawi. This trial was registered at www.clinicaltrials.gov as NCT00131235.
Department of Statistics and Actuarial Sciences, University of Hong Kong, PR China (JX); the Department of International Health, University of Tampere School of Medicine, Tampere, Finland (ML, TK, PA, and YBC); the Sexual and Reproductive Health Unit, National Institute for Health and Welfare, Helsinki, Finland (TK); the Department of Paediatrics, Tampere University Hospital, Tampere, Finland (PA); and the Center for Quantitative Medicine, Duke-National University of Singapore Graduate Medical School, Singapore (YBC).
Jiajun
J
Xu
Mari
M
Luntamo
Teija
T
Kulmala
Per
P
Ashorn
Yin Bun
YB
Cheung
D000293:Adolescent; D001724:Birth Weight; D015992:Body Mass Index; D017326:Clinical Trials, Phase III as Topic; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D005260:Female; D005865:Gestational Age; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008295:Malawi / Q000453:epidemiology; D008954:Models, Biological; D011247:Pregnancy; D011256:Pregnancy Outcome; D016032:Randomized Controlled Trials as Topic; D012015:Reference Standards; D015203:Reproducibility of Results; D015430:Weight Gain / Q000502:physiology*