Objective: To evaluate whether first trimester fetal heart rate (FHR) and nuchal translucency (NT) associate with preterm birth (PTB).
Methods: This was a comparative case-control study of 518 normal pregnancies with no history of PTB, of which 272 delivered at term (TB) and 246 progressed to spontaneous PTB prior to 37, 34, 32, and 28 weeks. Fetal heart rate (FHR) and NT values at the first-trimester scan were compared by means of univariable (Mann-Whitney) and multivariable logistic regression analysis considering hourglass membranes (HM) as the most severe PTB subgroup. Finally, severity trends for both parameters were investigated using correlations with gestational age (GA) at delivery and Kruskal-Walls tests.
Results: Regardless of GA at delivery, pregnancies affected with PTB showed higher FHR and thicker NT at the first trimester scan. The association was confirmed by the multivariable analysis and the severity trends, which paired the highest FHR and NT values with the most severe cases of PTB (p < .001) (p < .0001).
Conclusion: Fetuses with subsequent late, early and very early PTB show higher values of NT and FHR at the first-trimester scan.
Keywords: Preterm birth; fetal heart rate; first-trimester screening; nuchal translucency.