Animal studies have failed to reveal evidence of teratogenicity but have revealed evidence of fetotoxicity at maternally toxic doses; fetal body weights were reduced in rats at maternally toxic doses (minimally 0.4 times the human dose of both components based on body surface area [BSA] [mg/m2]). After intraperitoneal administration of tazobactam or piperacillin plus tazobactam in rats, decreased litter size (at 4 times the human dose of tazobactam based on BSA) and decreased litter size plus increase in fetuses with ossification delays and variations of ribs (at 0.5 times and 1 times the human dose of piperacillin and tazobactam, respectively, based on BSA) were observed in the presence of maternal toxicity. Both components cross the placenta in humans. There are no controlled data in human pregnancy.

AU TGA pregnancy category B1: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have not shown evidence of an increased occurrence of fetal damage.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

This drug should be used during pregnancy only if clearly needed and the benefit outweighs the risk to the fetus.

AU TGA pregnancy category: B1
US FDA pregnancy category: Not assigned.

Risk summary: Insufficient data on use of this drug in pregnant women to inform a drug-related risk.

See references

Use is considered acceptable; the benefit should outweigh the risk to the mother and infant. Caution is recommended.

Excreted into human milk: Yes (piperacillin [low levels]); Unknown (tazobactam)
Excreted into animal milk: Yes (tazobactam)

Comments:
-Developmental and health benefits of breastfeeding should be considered as well as the mother's clinical need for this drug.
-The effects in the nursing infant are unknown; potential side effects in the breastfed child due to this drug or the mother's underlying condition should be considered.
-Limited data indicate low levels of piperacillin in milk are not expected to cause harmful effects in the nursing infant.
-Tazobactam has not been studied in breastfeeding mothers.
-Disruption of infant's gastrointestinal flora (resulting in diarrhea or thrush) reported occasionally with penicillins, but such effects have not been adequately evaluated.

Piperacillin (4 g IV every 8 hours) was administered to 8 women for at least 3 days; milk levels were measured after 2 subsequent doses. In the 3 hours after each dose, milk levels ranged from 0.49 to 1.5 mg/L and 1.1 to 1.9 mg/L after the first and second dose, respectively; peak milk levels were reached 2 to 3 hours after dosing.

See references