Human use of acetaminophen (paracetamol) during pregnancy has not shown a clear association with birth defects, miscarriage, or adverse maternal or fetal outcomes; animal studies have demonstrated adverse events at clinically relevant doses. Acetaminophen is routinely used for short-term pain relief and fever in all stages of pregnancy and is believed to be safe in pregnancy when used intermittently for short durations.

Diphenhydramine studies in rats and rabbits have not revealed evidence of impaired fertility or fetal harm at doses up to 5 times the human dose. The Collaborative Perinatal Project reported 595 first-trimester exposures and 2,948 exposures anytime during pregnancy. No relationship was found to large categories of malformations. Possible associations with individual malformation were found. One study reported a statistical relationship between diphenhydramine use in the first trimester and cleft palate. One case of withdrawal in an infant whose mother ingested 150 mg per day of diphenhydramine has been reported. This infant developed tremor on the fifth day of life which was treated with phenobarbital. There are no controlled data in human pregnancy.

AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.

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.

Benefit should outweigh risk

AU TGA pregnancy category: Category A (acetaminophen/paracetamol)
AU TGA pregnancy category: Category A (diphenhydramine)
US FDA pregnancy category: Not assigned

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Larger doses or prolonged use of diphenhydramine may decrease the mother's milk supply, especially before lactation is well established. Effects may be minimized with single bedtime doses after the last feeding of the day. Non-sedating antihistamines are generally preferred when an antihistamine is needed. Acetaminophen (paracetamol) is considered compatible with breastfeeding by the American Academy of Pediatrics.

Use caution

Excreted into human milk: Yes

Comments:
-Occasional doses of diphenhydramine are not expected to adversely affect breastfed infant; however, larger doses or more prolonged use may cause drowsiness in breastfed infant and/or decrease mother's milk supply.
-Acetaminophen (paracetamol) is considered compatible with breastfeeding.

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