Fig. 1

Clarithromycin prevents preterm birth and improves neonatal survival induced by intra-amniotic injection of HMGB1. A Dams were intra-amniotically injected with HMGB1 in each sac under ultrasound guidance on 14.5 days post coitum (dpc) and treated with 75 mg/kg of clarithromycin (CLR; n = 15) or DMSO (vehicle control; n = 15) at 6, 12, 24, 48, 72, and 96 h post-injection. Dams were monitored until delivery, and neonates were followed until three weeks of age. B Gestational length (dpc) of dams intra-amniotically injected with HMGB1 and treated with CLR (blue dots) or DMSO (red dots). Data are represented as box-and-whisker plots with medians, interquartile ranges, and min/max ranges. P-value was determined using the one-sided Mann–Whitney U-test. C Rate of preterm birth of dams intra-amniotically injected with HMGB1 and treated with CLR (blue bar plot) or DMSO (red bar plot). P-value was determined using the one-sided Fisher’s exact test. D Kaplan–Meier survival curve showing the percentage of surviving neonates at 1, 2, and 3 weeks of age from dams intra-amniotically injected with HMGB1 and treated with CLR (blue line) or DMSO (red line). P-value was determined using the Mantel-Cox test. E–G Neonatal weights per litter at 1, 2, and 3 weeks of age from dams intra-amniotically injected with HMGB1 and treated with CLR [blue dots, 2–6 (mean = 3.8) neonates/litter] or DMSO [red dots, 1–2 (mean = 1.5) neonates/dam]. Data are represented as box-and-whisker plots with medians, interquartile ranges, and min/max ranges. P-value was determined using the one-sided Mann–Whitney U-test