A longitudinal study of gender differences in fetal heart rate patterns

B. Maghak, J. Dipietro, K. Costigan, N. Cnllan

Research output: Contribution to journalArticlepeer-review


OBJECTIVE: To examine gender differences in fetal heart rate (FHR) patterns at various gestational ages (GA) in a low-risk population. STUDY DESIGN: This was a prospective cohort study of 55 women of middle to upper socioeconomic status who underwent electronic fetal monitoring for 50 minutes at 24, 30, and 36 weeks GA. Tracings were then reviewed by a physician who was blinded as to the sex of the fetus, and the outcome of the pregnancy. Tracings were reviewed for baseline FHR, short-term and long-term variability, number of accelerations and decelerations, and time to reactivity for each GA. RESULTS: Of 55 patients enrolled in the study, there was one fetal demise secondary to trisomy 18 and one preterm dcliveiy at 31 weeks, leaving 53 patients available for analysis. The study group consisted of 32 male fetuses and 21 female fetuses. Average FHR was noted to decrease as (iA increased. The average FHR for male infants was lower than for female infants at each GA, although the difference was not statistically significant. A trend was noted across all three GA's for a greater number of FHR accelerations in males, a difference which became statistically significant at 36 weeks (p = 0.02). Higher proportions of male infants were reactive at 24 weeks (56%) than female infants (32%) (p = 0.07). Male infants required significantly less time to achieve reactivity at 30 weeks than female infants (9.8 minutes versus 15.8 minutes; p = 0.012). All infants in this study were reactive at 30 weeks GA and 46% were reactive as early as 24 weeks of age. CONCLUSION: Differences exist in utero between male and female fetuses in the third trimester of pregnancy with males having a shorter time to reactivity at 30 weeks, a greater number of accelerations at 36 weeks, and a trend toward lower baseline FHR. In addition, male fetuses had a greater tendency to be reactive at 24 weeks.

Original languageEnglish (US)
Pages (from-to)S132
JournalActa Diabetologica Latina
Issue number1 PART II
StatePublished - Dec 1 1997

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Endocrinology


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