The predictive value of first trimester fetal volume measurements, a prospective cohort study

Objectives To determine if fetal volume (FV) measurements with three-dimensional ultrasound in the first trimester of pregnancy can detect the fetus at risk for preterm birth and/or low birth weight. Methods In this prospective cohort study, 538 participants were included during the routine first trimester ultrasound examination. Volume measurements were performed with VOCAL (9°). Firstly, the relation between FV and gestational age for a set of participants with normal pregnancies (training set), was assessed using multiple linear regression analysis, which was then used to determine the expected normal values. Secondly, for a new set of participants with normal pregnancies and a set of participants with complicated pregnancies (preterm birth and/or low birth weight), i.e. the validation set, the observed fetal volumes (FVobserved) were compared with their expected normal values (FVexpected) and expressed as a percentage of the expected normal value. The difference in mean percentage was then assessed with independent-samples t-test. Finally, logistic regression analysis was applied to the validation set to analyze the ability to predict the pregnancy outcome with FV calculation. Results Linear regression analysis of FV as a predictor of preterm birth and/or low birth weight did not result in significant (p = 0.630 and 0.290, respectively) or clinical relevant results (standardized effect sizes of 0.061 and 0.179, respectively). The predicting quality was also very low (AUC = 0.508 and 0.545 respectively). Conclusions Fetal volume measurements in the first trimester of pregnancy are not useful as a prognostic tool for predicting pregnancies of high risk for preterm birth or a low birth weight