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Faculty have requested this content not be shared on social media
CME Credit Offered
CME Credit Offered
Abstract Award
Abstract Award
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Poster Session 2

(634) Female versus Male Fetuses—Variation in Fetal Heart Rate Tracing and Adverse Outcomes at Term

Thursday, January 30, 2025
4:00 PM – 6:00 PM  
Objective: To compare the fetal heart rate tracing (FHRT) and adverse outcomes among female versus male newborns delivered at term (> 37 weeks). We hypothesized that compared to female, pregnancies with male fetuses will have more frequent FHRT abnormalities and adverse outcomes.

Study Design: The inclusion criteria of the retrospective study were non-anomalous singletons, delivered at > 37 weeks after labor, whose sex at birth was either female or male. The consecutive deliveries occurred over 15 months. Using the guidelines by ACOG (Practice Bulletins 106 and 116), clinicians—blinded to maternal characteristics, gender, and outcomes—interpreted the FHRT for the last 120 min of labor. Composite neonatal and maternal adverse outcomes (CNAO and CMAO) were compared between the groups. Adjusted odds ratio (aOR) and 95% confidence intervals (CI) were calculated.

Results: Of the 5,160 deliveries during the study period, 3,165 (61%) met the inclusion criteria and among them 1,514 (48%) were female and 1,651 (52%), male. Compared to female, the FHRT among male was significantly more likely to have marked variability (P=0.044), and prolonged deceleration (P=0.039). The classification of FHRT as categories I, II or III were similar (Table 1). Cesarean delivery for non-reassuring FHRT was more common among male (11.3%) than female newborns (6.9%; aOR 1.67; 95% 1.30-2.14). CNAO for male (2.2%) was significantly higher than female newborns (0.9%; aOR 2.52; 95% CI 1.33-4.77). Apgar score < 7 at 5 min (aOR 3.12, 95% CI 1.26-7.77) was the component of the CNAO that differed significantly. CMAO was also significantly higher for individuals who delivered male (9.3%) vs female (6.3%; aOR 1.45, 95% CI 1.10-1.92) newborns (Table 2).  

Conclusion: Among singleton pregnancies delivered at term, male fetuses are significantly more likely to have abnormalities for fetal heart rate, and adverse outcomes to neonatal-maternal dyad. Investigations to elucidate the etiology and intervention trials to mitigate the disparate adverse outcomes are warranted.