UC San Diego

Objective: This study aimed to compare the patterns of fetal heart rate tracings (FHRTs), and outcomes among individuals with small (birth weight [BW] <10% for gestational age [GA]; SGA) versus appropriate (BW at 10-89% for GA; AGA) newborns at term (≥37.0 weeks). Study Design: Our retrospective cohort study included consecutive deliveries over 15 months at a level IV center. FHRTs were reviewed by obstetricians blinded to maternal and neonatal outcomes. The inclusion criteria were non-anomalous singletons, cataloged as SGA or AGA birth weight using Alexander et al's nomogram. In 20-minute segments, the last 120 minutes of tracing were characterized. Rates of cesarean delivery (CD) and composite neonatal adverse outcomes (CNAOs) were compared. Results: Of 5,160 deliveries, 3,029 (58.7%) met the inclusion criteria, and among them, 422 (13.9%) were SGA and 2,607 (86.1%) AGA. There were no differences in FHRT baseline, variability, or accelerations. Compared to AGA, SGA was more likely to have prolonged decelerations (11.8 vs. 8.4%, p = 0.021), and recurrent decelerations with ≥50% of contractions (21.3 vs. 16.5%, p = 0.014). Overall, the presence of category II FHRT or not was similar between the SGA (91.2%) and AGA (88.5%; p = 0.097). Persistent category II FHRT was significantly more common among SGA (37.4%) than AGA (28.1%; aOR = 1.47; 95% CI: 1.47-1.82) newborns. The rate of CD for non-reassuring FHRT was similar among the two groups. CNAO occurred in 1.4% in both SGA and AGA neonates (p = 0.95). Conclusion: In our cohort of those with fetal monitoring prior to delivery at ≥37 weeks, persistent category II FHRT at the end of labor was significantly more common in SGA compared to AGA neonates; however, composite neonatal morbidity did not differ between the two groups. Our analysis provides data for shared decision-making that among SGA newborns, abnormalities of FHRT are not linked with adverse outcomes. Key Points: · There were no differences in FHRT baseline, variability, or accelerations between AGA and SGA.. · SGA was more likely to have prolonged decelerations and recurrent decelerations with ≥50% of contractions.. · Persistent category II FHRT before delivery is significantly more common with SGA than AGA.. · FHRT abnormalities, however, were not associated with CD for non-reassuring FHRT, or adverse outcomes..