Animal studies of omeprazole have revealed evidence of dose-related increase in bone resorptions/fetal resorptions, embryotoxicity/lethality, and changes in bone morphology; animal studies using rifabutin have revealed evidence of increased skeletal anomalies and decreased fetal viability at doses reaching maternal toxicity. Animal studies using amoxicillin have failed to reveal evidence of adverse developmental effects at doses up to 3 grams. There are no controlled data using any of the drugs, alone or in combination, in human pregnancy.

A retrospective cohort study has failed to reveal evidence of increased malformations, low birth weight, and/or low Apgar scores in patients who took omeprazole during the first trimester. Epidemiological studies and case reports have not established a drug-associated risk of adverse maternal or fetal outcomes, major birth defects, or miscarriage with amoxicillin.

Male animal studies have revealed evidence of impaired fertility after administration of rifabutin doses 32 times the recommended human daily dose.

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 not recommended.

US FDA pregnancy category: Not assigned.

Risk Summary: Malformative risk with use of omeprazole in pregnant women is unlikely. There are no adequate and well-controlled study data available on use of amoxicillin or rifabutin in pregnant women to inform of a drug-related risk.

Comments:
-Use of adequate, non-hormonal, highly effective methods of contraception should be encouraged during treatment.
-If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential harm to the fetus.

See references

A decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

Excreted into human milk: Yes (amoxicillin, omeprazole); Unknown (rifabutin)
Excreted into animal milk: Unknown (rifabutin)

Comments:
-Maternal amoxicillin use may result in harm in a nursing infant (e.g., diarrhea).
-The effects of omeprazole and rifabutin in the nursing infant or on lactation are unknown.
-The American Academy of Pediatrics considers amoxicillin compatible with breastfeeding, and that omeprazole should be avoided until additional studies can confirm the safe use of this drug during breastfeeding.

See references