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Background:The heart is formed between 18-56 days of gestation. Rhythmic contractions of the foetal heart that originates from pacemaker cells spontaneously depolarize around 3 weeks after conception. The advent of high-resolution transvaginal ultrasound (TVS) and knowledge of the ultrasound appearances of normal early pregnancy development and a good understanding of its pitfalls are essential for the diagnosis and management of early pregnancy failure.
Objective: To study the relationship of foetal heart rate (FHR) at 6-7 weeks of gestation and the outcome of pregnancy at the end of first trimester.
Materials and methods:This prospective observational study was conducted at A.J. Institute of Medical Sciences and Research Centre, Mangalore from January 2019 – December 2019. A total of 432 pregnant women included in the study underwent transvaginal ultrasound for confirmation of a single viable gestation. The foetal heart rate (FHR) was thence noted. The patients were then followed up and a repeat ultrasound was done for all pregnancies that continued beyond 12 weeks to confirm continuation of viable pregnancy. All pregnancies that did not continue till 12 weeks were noted. Pregnancies which were terminated in the presence of a viable foetus were excluded from the study.
Results: A total of 432 pregnant women were referred for 6-7 weeks ultrasound from January 2019 - December 2019. However, five pregnant women were excluded; four due to non-viable foetus and one for medical termination of pregnancy inspite of a viable pregnancy. Out of the 427 pregnant women included; 423 had an FHR ≥100bpm and four had FHR <100 bpm at 6 - 7 weeks ultrasound. Intrauterine foetal demise was noted in 3 of the 4 patients with an FHR <100bpm whereas no intrauterine foetal demise was noted in patients with FHR ≥100bpm at 6 - 7 weeks ultrasound. The sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 99.7%, 75%, 100% respectively.
Conclusion: The study concluded that the absence of foetal bradycardia at 6 - 7 weeks ultrasound was associated with continuation of pregnancy beyond first trimester. In the presence of foetal bradycardia there is a high likelihood of pregnancy loss before the end of first trimester.
Keywords: Foetal heart rate; Foetal bradycardia; Intrauterine foetal demise