In animal studies dosed from 2 weeks prior to mating through organogenesis, no effects on embryo-fetal development were observed in pregnant rats receiving approximately 38 times (2000 mg/kg/day) or pregnant rabbits receiving approximately 6 times (1000 mg/kg/day) the maximum human maintenance dose. Among pregnant rats receiving oral drug from organogenesis through lactation, decreased growth of offspring was observed at 500 mg/kg/day and higher, and reduction in offspring survival during lactation was observed at 2000 mg/kg/day. Maternal toxicity described as impaired weight gain and approximately 10% mortality occurred at 2000 mg/kg/day. Pregnant women with urea cycle disorders, PA, and MMA may experience an increase in catabolic stress which can trigger a hyperammonemic crisis both in the intrapartum and in the post-partum (3 to 14 days post-partum) periods. Maternal complications related to
hyperammonemic crisis can include neurological impairment, coma and in some cases death. There are no adequate and well controlled studies in pregnant women.

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.

Use is acceptable; use caution

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

Risk Summary: Data for use in pregnant women are insufficient to inform a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes; however, untreated NAGS (N-acetylglutamate synthase) deficiency, PA (propionic acidemia) or MMA (methylmalonic acidemia) can result in irreversible neurologic damage and death in pregnant women.

Comments:
-There is a pregnancy exposure registry that monitors pregnancy outcomes in women with NAGS deficiency; healthcare providers should report exposure by calling 1-888-575-8344

See references

An increase in mortality and impairment of body weight gain has been observed in neonatal rats nursed by mothers receiving this drug. The developmental and health benefits of breastfeeding should be considered along with the
mother's clinical need for this drug and any potential adverse effects on the breastfed child from this drug or from the underlying maternal condition.

Benefit should outweigh risk

Excreted into human milk: Unknown
Excreted into animal milk: Yes

Comments:
-There are no available data on the effects of this drug on the breastfed infant or the effects on milk production.
-Some authorities contraindicate use of this drug during lactation due to an increase in mortality and impairment of body weight gain that was reported in neonatal rats nursed by mothers receiving this drug.

See references