EP04.07: Fetal growth in fetuses exposed to syphilis

The aim of this study is to describe the effects of maternal syphilis on fetal growth parameters and growth velocity during pregnancy. Prospective study of 42 pregnant subjects who were diagnosed and treated for syphilis according to the CDC 2021 guidelines. Serial ultrasound (US) evaluations were performed > 20 weeks gestation either prior to, or within 7 days of indicated treatment. Fetal growth was assessed every 4 weeks if the estimated fetal weight (EFW) was above the 10th percentile for gestational age (GA), or every 2 weeks if the EFW was less than the 10th percentile, until delivery. A drop in fetal growth was defined as a 20% reduction in EFW, and a severe drop as a 40% reduction from the original percentile when comparing the first and last percentiles. EFW z-scores between the first and last scan were analysed. Additionally, the drop in growth of each biometric parameter (BPD, HC, AC, femur length (FL), and humerus length (HL) was estimated. Median GA at first scan was 20 weeks (13-34) and at last scan 35 weeks (32-38) with a median number of scans n = 3 (2-10). Median EFW percentile at first scan was 39th (4-99th) with 66.6% of fetuses <p50th, 18% <p25th, and 3.7% <10th. At last scan, median EFW was significantly lower at the 23th percentile (2-95th) with 71.4% <p50th, 50% <p25th, and 14.3% <10th. EFW z-score at first scan was (mean/SD) 0.52 (0.9) and at last scan -0.09 (0.9); p = 0.05. At birth, 78% of newborns had birthweight <50th, 56% <25th and 12% <10th. A 20% drop in EFW was observed in 57.1% (24/42) of fetuses, and a 40% drop in 42.8% (18/42). Among biometric parameters, FL more frequently demonstrated a 20% drop in growth percentile (66%, 28/42), followed by HC (55.5%, 23/42), AC (45% 19/42), DBP 40.0% (17/42) and HL (33% 14/42). Of all fetuses exposed to syphilis in this cohort, 42% experienced a 40% drop in estimated fetal weight (EFW) percentile during gestation, primarily seen in a decrease in femur length and biparietal diameter.