Heart Activity Visualization in Embryos with Crown-Rump Length Shorter Than 5 mm and Its Role in Prediction of Early Pregnancy Failure in Patients of Recurrent Early Pregnancy Loss

Background: Previously, only embryos with a crown-rump length (CRL) of ≥5 mm could have their heart activity seen using ultrasonography. However, due to advancements in ultrasound resolution, viable embryos with CRL as small as 2 mm may now be diagnosed. Objective: The current study aimed to investigate whether early embryonic heart rate (EHR) in embryos with smaller CRL may be used as a predictor of pregnancy outcome.
Methods: This prospective cohort study included 78 cases, from June 2023 to May 2024. All women had a history of recurrent pregnancy. Early transvaginal ultrasound was done with EHR and was assessed using M-mode. Follow-up was done to determine the outcome of the pregnancy after 12 weeks. The negative outcome manifested as a spontaneous pregnancy loss that transpired at or prior to 12 weeks of gestation.
Results: A normal CRL diameter was present in 79.6% of the CRL in the examined groups. With cases of normal diameter that ended in miscarriage, only one had a CRL that lasted past the first trimester. With a total accuracy of 99.1%, CRL's sensitivity and specificity for miscarriage prediction were 98.6% and 100%, respectively. With a total accuracy of 98.1%, When anticipating a first-trimester pregnancy outcome, EHR's overall accuracy was 98.2%, with specificity of 100% and sensitivity of 97.4%. Conclusion: These days, most embryos with a CRL of 2 to 5 mm can show cardiac activity. About 80% of the time, non-visualization at this point is linked to embryonic death. A poor pregnancy outcome is linked to both embryonic bradycardia and small CRL.