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2018, BJOG : an international journal of obstetrics and gynaecology
To assess external validity of all published first trimester prediction models based on routinely collected maternal predictors for the risk of small- and large-for-gestational-age infants (SGA and LGA). Furthermore, the clinical potential of the best performing models was evaluated. Multicentre prospective cohort SETTING: 36 midwifery practices and six hospitals (Netherlands) POPULATION: Pregnant women <16 weeks of gestation were recruited between July 1, 2013 and December 31, 2015. Prediction models were systematically selected from the literature. Information on predictors was obtained by a web-based questionnaire. Birth weight centiles were corrected for gestational age, parity, fetal sex, and ethnicity. Predictive performance was assessed by means of discrimination (c-statistic) and calibration. The validation cohort consisted of 2582 pregnant women. The outcomes SGA 90th percentile were present in 203 and 224 women, respectively. The c-statistics of the six included models for SGA ranged from 0.52 to 0.64 and for the six included models for LGA from 0.60 to 0.69. All models yielded higher c-statistics for more severe cases of SGA (95th percentile). Initial calibration showed poor to moderate agreement between predicted probabilities and observed outcomes, but improved substantially after recalibration. The clinical relevance of the models is limited because of their moderate predictive performance and because the definitions of SGA and LGA do not exclude constitutional small or large infants. As most clinically relevant fetal growth deviations are 'vascular' or 'metabolic' related, models predicting hypertensive disorders and gestational diabetes are likely to be more specific. This article is protected by copyright. All rights reserved.