Objective To assess ampicillin levels according to the duration of intrapartum antibiotic prophylaxis (IAP).
Design Prospective cohort single-centre study.
Setting Tertiary care centre (Modena, Italy).
Patients 120 neonates≥35 weeks’ gestation exposed to IAP.
Interventions Neonates were divided into four groups, according to the duration of IAP prior to delivery: group 1 (n=30; <1 hour), group 2 (n=30; ≥1 and <2 hours), group 3 (n=30; ≥2 and <4 hours) and group 4 (n=30; ≥2 doses, ≥4 hours).
Main outcome measures Blood samples were collected at delivery (from the umbilical cord) and at age 4 hours (from a peripheral vessel).
Results Median duration of IAP was 121 min (range 7–2045 min). Median ampicillin levels in umbilical cord blood were 10.4 µg/mL (IQR 6.4–14.9) and in peripheral blood were 4.7 µg/mL (IQR 2.8–6.4µg/mL). Umbilical cord blood levels reached a peak approximately 30 min after IAP and then declined significantly (p<0.001). Peripheral blood levels did not differ among study groups. Neonates exposed to a full loading dose (n=115) had peripheral blood levels 2.5–70 times higher than the minimal inhibitory concentration for group B streptococcus. There was no relationship between neonatal ampicillin concentrations and the duration of IAP prior to delivery (β=−0.0003, 95% CI −0.02 to 0.001, p=0.680).
Conclusions Ampicillin levels reach a peak in the umbilical cord blood within 30 min of intrapartum administration. After a full loading dose, bactericidal levels persist for at least 4 hours after birth and seem independent of the duration of IAP prior to delivery.
- Group B Streptococcus
- Intrapartum antibiotic prophylaxis
- Early-onset sepsis
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Contributor All authors made substantive intellectual contributions to the published study and approved the final manuscript as submitted. AB and ZP designed the study and drafted the initial manuscript. MLBR and DG carried out the initial analyses, reviewed and revised the manuscript. KR and VB designed the data collection instrument, coordinated and supervised data collection and critically reviewed the manuscript. FFa and FFe conceptualised and designed the study, reviewed and revised the manuscript.
Competing interests None declared.
Ethics approval The study protocol was approved by the ethical committee of the Azienda Ospedaliero-Universitaria of Modena (Italy) on 8 November 2013 (Protocol no 159/13).
Provenance and peer review Not commissioned; externally peer reviewed.
Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with ’BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.