RESUMEN
Background: Fetal heart rate is an indicator of fetal viability. During third trimester and labour the normal range of fetal heart rate is between 110-160 bpm as recommended by the international guidelines. Unlike this, the first trimester embryonic heart rate does not lie in the same range. During the first trimester the normal embryonic heart rate varies between each week of gestation, as determined by a few western studies. Indian studies on the same are not available. Objective of this study was to determine the trend of the fetal heart rate in first trimester of pregnancy in South Indian women.Methods: Transvaginal scan was done in 51 pregnant women with singleton pregnancy attending the antenatal clinic in a medical college hospital. Crown rump length and fetal heart rate were measured and plotted on a graph. Also, the fetal heart rate at different gestational age of our study was compared with the fetal heart rates at the same gestational age from the studies in the western population.Results: The range of fetal heart rate at different weeks of gestation was comparable to the heart rate variations as seen in the western population. The maximum heart rates at 9 weeks of gestation in our study was higher than the heart rate in the western population.Conclusions: Possibility of variation in the fetal heart rates in the first trimester in different populations cannot be ruled out until confirmed by studies with large sample size.