Background: Adverse outcomes of pregnancy are a challenging health-care problem. Prediction of adverse pregnancy outcomes is important to prevent the morbidities of the foetus and the mother.
Aims: To study the clinical interest of fetal nasal bone length in predicting adverse pregnancy outcomes in the first trimester of pregnancy.
Study Design: A population-based retrospective cohort study.
Methods: Data from 868 women with first-trimester fetal nasal bone length and birth records available were enrolled. Fetal nasal bone length percentiles were determined and evaluated for their ability to predict adverse pregnancy outcomes such as preterm birth, preterm labour, preterm premature rupture of membranes, early preterm birth, gestational diabetes mellitus, gestational hypertension-preeclampsia, small-for-gestational age foetuses, macrosomia, oligohydramnios, polyhydramnios and fetal distress.
Results: Fetal nasal bone length >95^th percentile was significantly associated with preterm labor and preterm premature rupture of membranes (p=0.02, accuracy 0.91 and p=0.001, accuracy 0.94, respectively), whereas nasal bone length >99^th percentile was significantly associated with preterm labor and oligohydramnios (p=0.006, accuracy 0.95 and p=0.014, accuracy 0.97).
Conclusion: Fetal nasal bone length at high percentiles in the first trimester of pregnancy may aid in the prediction of adverse outcomes such as preterm labour, preterm premature rupture of membranes and oligohydramnios.

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