Fetal Heart Rate at 12 Weeks' Gestation and the Risk of Preterm Birth: A Prospective Validation Study

Area of Science:

• Maternal-Fetal Medicine
• Obstetrics
• Reproductive Health

Background:

• Preterm birth (PTB) remains a leading cause of neonatal morbidity and mortality.
• Early identification of pregnancies at risk for PTB is crucial for timely intervention.
• First-trimester screening markers are being investigated to predict adverse pregnancy outcomes.

Purpose of the Study:

• To prospectively validate the association between fetal heart rate (FHR) measured at the 12-week scan and the risk of preterm birth (PTB).
• To assess the predictive value of FHR for spontaneous preterm birth (sPTB), including early-onset sPTB (<34 weeks).
• To evaluate the combined predictive performance of FHR with other first-trimester parameters for sPTB.

Main Methods:

• Prospective cohort study of 1276 singleton pregnancies.
• Fetal heart rate (FHR) measured at 11-13+6 weeks' gestation.
• Logistic regression and ROC curve analyses incorporating clinical, sonographic, and biochemical markers (free-βhCG).

Main Results:

• Higher FHR at 12 weeks was significantly associated with PTB and sPTB.
• FHR was the only consistent predictor of PTB and sPTB in univariable analysis.
• Multivariable models showed FHR predicted sPTB <34 weeks (AUC 0.73), improving to AUC 0.81 when combined with free-βhCG.

Conclusions:

• Elevated FHR at the 12-week scan is a significant predictor of spontaneous preterm birth, particularly before 34 weeks' gestation.
• FHR, especially when integrated with free-βhCG, shows potential for enhancing early first-trimester screening strategies for sPTB.
• These findings support the inclusion of FHR in first-trimester risk assessment for spontaneous preterm birth.