IV formulation: This drug should not be used during pregnancy unless the benefit outweighs the risk.
Oral formulation: This drug should be used during pregnancy only if clearly needed and the benefit outweighs the risk.

AU TGA pregnancy category: B2
US FDA pregnancy category: Not assigned.

Risk summary: Malformative risk with use of this drug in pregnant women is unlikely.

Comments:
-According to some authorities: At this time, single-dose antibacterial regimens are not appropriate to treat urinary tract infections in pregnant women.

Animal studies have failed to reveal evidence of teratogenicity, but have revealed evidence of fetotoxicity secondary to maternal toxicity (maternal deaths, body weight losses). When administered as the sodium salt (IM injection) in humans, this drug crosses the placental barrier. There are no controlled data in human pregnancy; however, safety data on pregnant women are available (moderate amount) and do not show any malformative or fetal/neonatal toxicity of this drug.

In early clinical studies and postmarketing experience, at least 1400 pregnant women used this drug (usually a single 3 g oral dose) during pregnancy, most during the second and third trimesters. Based on review of human data, there is no evidence that this drug is associated with adverse fetal or maternal outcomes or teratogenicity.

A single 3 g oral dose was given (in water) to 153 pregnant women with bacteriuria. Infecting organisms were eradicated in 96% of patients, with recurrence rate of 3% after 25 to 30 days. Minimal maternal side effects occurred and no serious adverse fetal effects were documented. The trimester in which the drug was administered was not reported.

AU TGA pregnancy category B2: 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 are inadequate or may be lacking, but available data show no 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.

See references

Use is not recommended unless the benefit outweighs the risk; a decision should be made to discontinue breastfeeding or discontinue/abstain from the drug, taking into account the importance of the drug to the mother and the benefit of breastfeeding to the infant.
-According to some authorities: Use of a single oral dose is considered acceptable.

Excreted into human milk: Yes (low levels)

Comments:
-The effects in the nursing infant are unknown; low levels in milk not expected to cause harmful effects in the nursing infant, especially if older than 2 months.

Low levels were found in human milk (about 8% of serum levels).

After 1 to 2 g via injection, colostrum levels in 2 women were 4.8 mg/L and milk levels were 3.6 mg/L.

See references