Statistically Significant Difference in the First-trimester Fetal Heart Rate between Genders?
Background: The study aims to establish the pattern of fetal heart rates in the first and second trimesters and determine whether there is a statistically significant difference in the first-trimester fetal heart rate (FHR) of males and females.
Methods: This retrospective observational research is a study of FHRs measured at 11+0–13+6 wk and 18+0–23+6 wk, and ultrasound scan-diagnosed fetal sex at 18+0–23+6 wk. Singleton fetuses with nonambiguous external genitalia were recruited. The FHR was measured in B or M mode with Pulsed Wave Doppler, while ultrasound appearance of external genitalia determined the fetal sex at 18+0–23+6 wk. Student’s t-test and Chi-square test were used for data analysis, and statistical significance was set at p < 0.05.
Results: A total of 2437 pregnancies meeting the study criteria were analyzed. The fetal sexes were 1398 (57.4%) males and 1039 (42.6%) females. There was no statistically significant difference in the first-trimester FHR between males and females (p = 0.74). However, females had higher mean FHR in both the first and second trimesters (First trimester: 165.4 ± 18.2 bpm vs 163.2 ± 17.1 bpm and Second trimester: 150.9 ±22.6 bpm vs 141.9 ±23.1 bpm). The FHR reduces with the increase in gestational age.
Conclusion: There is no statistically significant difference in the first-trimester FHRs between sexes.
statistically significant difference, fetal heart rates, fetal sexes, first trimester, ultrasound scan
 Igbinedion, B. O. E. and Akhigbe, T. O. (2012). The accuracy of 2D ultrasound prenatal sex determination. Nigerian Medical Journal, vol. 53, pp. 71–75.
 Mehmet, S., Vehbi, Y. T., and Şebnem, A. T. (2019). An appropriate way to predict fetal gender at first trimester: Anogenital distance. The Journal of Maternal-Fetal & Neonatal Medicine, vol. 32, no. 12, pp. 2012–2016.
 Ahankari, A. S., Myles, P., Tata, L. J., et al. (2015). Banning of fetal sex determination and changes in sex ratio in India. The Lancet, vol. 3, pp. e523–e524.
 Jylhä, M. E., Kirkinen, P. P., Puura, K. L., et al. (2010). Fetal sex determination: Obstetricians’ attitudes in antenatal screening units in Finland. Scandinavian Journal of Public Health, vol. 38, no. 7, pp. 756–760.
 Bhide, A. and Acharya, G. (2018). Sex differences in fetal heart rate and variability assessed by antenatal computerized cardiotocography. Acta Obstet Gynecol Scand, vol. 97, pp. 1486–1490.
 Mediuw, D., Widiasih, R., and Napisah, P. (2019). Health technologies for detecting high risk conditions in pregnancy: A systematic review. Journal of Nursing Care, vol. 2, no. 3, pp. 202–222.
 McKenna, D. S., Ventolini, G., and Neiger, R. (2006). Downing gender-related differences in fetal heart rate during first trimester. Fetal Diagnosis and Therapy, vol. 21, no. 1, pp. 144–147.
 Sipahi, M., Tokgöz, V. Y., and Tosun, Ş. A. (2018). An appropriate way to predict fetal gender at first trimester: Anogenital distance. Journal of Maternal-Fetal and Neonatal Medicine, vol. 32, no. 12, pp. 2012–2016.
 Bracero, L. A., Seybold, D. J., and Witsberger, S., et al. (2018). First trimester fetal heart rate as a predictor of newborn sex. Acta Obstetricia et Gynecologica Scandinavica, vol. 97, no. 12, pp. 1486–1490.
 Genuis, S., Genuis, S. K., and Chang, W. C. (1996). Antenatal fetal heart rate and “maternal intuition” as predictors of fetal sex. Journal of Reproductive Medicine, vol. 41, no. 6, pp. 447–449.
 Fetal Medicine Foundation. (n.d.). London protocols. Fetal Medicine Foundation. Retrieved from www.fmf.org
 ISUOG Practice Guidelines. (2013). Performance of first-trimester fetal ultrasound scan. Ultrasound in Obstetrics and Gynecology, vol. 41, pp. 102–113.
 Zavala, J. H., Myers, M. M., and Fifer, W. P. (2020). Assessment of autonomic function in the late term fetus. The effects of sex and state. Developmental Psychobiology, vol. 62, no. 2, pp. 224–231.
 Aibar, L., Puertas, A., Valverde, M., et al. (2012). Fetal sex and perinatal outcomes. Journal of Perinatal Medicine, vol. 40, pp. 271–276.