Are postnatal ampicillin levels actually related to the duration of intrapartum antibiotic prophylaxis prior to delivery? A pharmacokinetic study in 120 neonates

Arch Dis Child Fetal Neonatal Ed. 2018 Mar;103(2):F152-F156. doi: 10.1136/archdischild-2016-312546. Epub 2017 Jun 29.


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.

Keywords: Early-onset sepsis; Group B Streptococcus; Intrapartum antibiotic prophylaxis; Newborn.

MeSH terms

  • Ampicillin / administration & dosage*
  • Ampicillin / pharmacokinetics*
  • Anti-Bacterial Agents / administration & dosage*
  • Anti-Bacterial Agents / pharmacokinetics*
  • Anti-Bacterial Agents / therapeutic use
  • Antibiotic Prophylaxis / methods*
  • Female
  • Fetal Blood / chemistry
  • Humans
  • Infant, Newborn
  • Italy
  • Microbial Sensitivity Tests
  • Pregnancy
  • Prospective Studies
  • Streptococcal Infections / prevention & control*
  • Streptococcus agalactiae
  • Vagina / microbiology


  • Anti-Bacterial Agents
  • Ampicillin