Is diphenhydramine safe during pregnancy?

What does the evidence say about diphenhydramine during pregnancy?

1. Studies so far haven't shown that diphenhydramine raises the chance of birth defects above the usual background rate. 1
2. Diphenhydramine has long been used to relieve allergy symptoms and occasional sleeplessness in pregnancy, though it does cross the placenta. 1
3. Continued high-dose use near delivery has been linked to sleepiness in newborns, and a small number of reports describe withdrawal-like symptoms after birth, which is why using the lowest effective dose late in pregnancy matters. 1
4. The FDA-approved label caps standard adult dosing at 25 to 50 mg every 4 to 6 hours, up to 300 mg a day, and many combination cold or sleep products already contain diphenhydramine, so it's worth checking labels to avoid doubling up. 2

Is diphenhydramine safe in each trimester?

• First trimester. Occasional use for allergy flare-ups or short-term sleep trouble is generally fine at standard over-the-counter doses.
• Second trimester. Same guidance applies. For daily allergy control, many providers prefer second-generation antihistamines like cetirizine or loratadine since they cause less drowsiness.
• Third trimester. Check with your provider as delivery gets closer. A few case reports link antihistamine use right around labor to sleepiness or withdrawal-like symptoms in newborns.