0853 Fetal Heart Rate Variability Increases During Maternal Sleep Apnea Events

Introduction While studies have established that SDB during pregnancy increases the risk of adverse maternal outcomes, fetal effects are less well studied. Evidence suggests that fetal heart rate decelerations, an indicator of fetal distress, may be elicited by SDB. We examined the relationship between maternal SDB events and fetal heart rate (FHR) and fetal heart rate variability (FHRV). Methods Obese (BMI≥30kg/m2) non-smoking women carrying singleton fetuses underwent overnight polysomnography (34-37 weeks gestational age), with simultaneous fetal heart rate monitoring. Standard methods were used to score sleep, SDB events (apneas/hypopneas) and to analyze fetal heart rate parameters. Using linear mixed effect models, we examined changes in mean FHR and FHR variability (expressed by FHR SD) between the 10-second period immediately before individual SDB events, during events to the end of the associated oxygen desaturation period, and the 10-second period immediately following the SDB event. Results Valid PSG and FHR data were obtained from 85 third trimester maternal-fetal dyads. Across all participants, there were 2779 maternal SDB events (apneas or hypopneas). Mean AHI for individual subjects was 9.04 (SD 13.75). 39 women had OSA (AHI≥5), which was mostly mild. Mean FHR did not change significantly during and after episodes of SDB episodes compared to pre-event FHR, and did not change afterwards compared to during events, in unadjusted or adjusted (sleep stage, apnea type, degree of desaturation, age) analyses. In unadjusted analyses, FHRV significantly increased during SDB episodes compared to pre-SDB FHRV. After SDB events, FHRV was significantly lower than during SDB events. In fully adjusted models, these findings remained highly significant. FHRV was not significantly different after SDB events compared to pre-SDB event FHRV in unadjusted or adjusted models. Conclusion We observed consistent changes in FHR variability during and after maternal SDB events. Mean FHRV significantly increased during maternal SDB episodes compared to baseline FHRV, and decreased after SDB episodes. In contrast, mean FHR did not change significantly before, during and after SDB episodes. These data demonstrate that the fetus reacts to maternal SDB events, and raise questions about persistent effects of maternal SDB on the developing fetus. Support NIH HD079411