Yolk sac size and embryonic heart rate as prognostic factors of first trimester pregnancy outcome

Abstract

Objectives: To investigate embryonic heart rate (EHR) and yolk sac diameter (YSD) during the first trimester and their role as prognostic markers of first trimester pregnancy outcome.

Study design: Prospective cohort study involving 219 women conducted in the 4th Academic Department of Obstetrics and Gynaecology, Aristotle University of Thessaloniki, Greece. Gestational age (GA) was determined ultrasonographically based on gestational sac diameter and crown-rump length. EHR and YSD were evaluated during the first 12 weeks and subsequently compared between the pregnancies that continued beyond the first trimester and those that resulted in spontaneous abortion. Receiver-operating characteristic (ROC) curves were used for the evaluation of the prognostic value of the combination of gestational age with embryonic heart rate and yolk sac diameter.

Results: The EHR and YSD were significantly correlated to advancing gestational age (p<0.001) in pregnancies continuing beyond 12 weeks. Pregnancies that resulted in spontaneous abortion exhibited a statistically significant lower EHR (p<0.001), smaller YSD (p=0.001) or absent yolk sac. ROC curve analysis demonstrated the predictive value of the combination of GA with EHR (area under the ROC curve: 0.971, p<0.001) and GA with YSD (area under the ROC curve: 0.858, p<0.001) for first trimester pregnancy outcome.

Conclusions: EHR and YSD progressively increase in healthy pregnancies during the first trimester. Embryonic bradycardia and absence of yolk sac or even a smaller yolk sac diameter than expected for any gestational age are predictors of poor pregnancy outcome during the first 12 weeks.