Naproxen

Pregnancy

MotherToBaby reports that most studies of NSAIDs, including naproxen, have not found more birth defects, while some studies report small increases in selected defects and the overall findings are mixed. Hernandez et al. (2012) used a case-control study in which naproxen was among the NSAIDs reported; it found a few class-level defect associations but does not isolate a naproxen-specific effect. Hultzsch et al. (2021) described 121 first-trimester naproxen exposures, 95 liveborn infants, and two major defects, but had no comparison group. In a 2026 Israeli cohort of 264,858 singleton pregnancies, 3,105 were naproxen-exposed; the matched estimate for major congenital malformations was 0.97 (95% CI 0.73 to 1.30). Dispensing does not prove ingestion, and the study excluded spontaneous abortions, so it does not answer miscarriage questions. Ekenze et al. (2026) reported naproxen adjusted odds ratios ranging from 1.15 to 1.28 across birth-defect severity groupings; the abstract does not provide individual confidence intervals, so the statistical strength of the individual estimates remains unclear. A 2026 French cohort included 4,857,907 pregnancies and 19,721 naproxen exposures; naproxen exposure was associated with miscarriage at HR 1.09 (95% CI 1.01 to 1.18). This observational estimate cannot establish cause; the database lacked indication, dose, and duration, could miss very early losses, and did not capture smoking or alcohol reliably. FDA labeling says observational data on other possible embryo-fetal risks in the first and second trimesters are inconclusive. Animal reproduction studies in rats, rabbits, and mice did not show teratogenicity at tested doses; this is not human evidence. The class-wide miscarriage and defect findings should not be presented as naproxen-specific unless the study analyzed naproxen separately.

Breastfeeding

LactMed describes low naproxen levels in milk, but its main milk-level evidence comes from a very small set of observations. One reported milk study measured naproxen in one mother; LactMed estimates an exclusively breastfed infant's maximum intake at 2.2 to 2.8% of the maternal weight-adjusted dose from the measured concentrations. Relevant infant blood-level data were not found by LactMed. LactMed reports a possible case of prolonged bleeding time, low platelets, and acute anemia in a 7-day-old infant whose mother also took bacampicillin; causation is uncertain. In a telephone follow-up of 20 naproxen-exposed infants, two mothers reported drowsiness and one reported vomiting, and none required medical care. The 1993 primary follow-up abstract describes a broader 838-infant medication cohort and does not identify the naproxen-specific subgroup; the infant-specific naproxen findings are attributed to LactMed. A small randomized post-cesarean trial compared naproxen with tramadol but found no difference in breastfeeding rates. The 2026 systematic review retained 34 studies across NSAIDs and acetaminophen and concluded that the evidence is not sufficient to establish whether lactating people should use NSAIDs; it does not provide a new naproxen-specific conclusion. LactMed and MotherToBaby say shorter-acting medicines may be preferred, particularly for newborn or preterm infants, because naproxen remains in the body longer.

What was tested

Pregnancy evidence includes large observational cohorts, case-control studies, and a small prospective case series. The 2026 French cohort studied miscarriage, while the 2026 Israeli cohort studied major congenital malformations and excluded pregnancy losses; they answer different questions. Most pregnancy data use prescriptions or dispensings rather than confirmed ingestion, and indication, dose, duration, and unrecorded over-the-counter use are limitations. Later-pregnancy evidence includes observational cohorts and postmarketing reports, often for NSAIDs as a class rather than naproxen alone. Breastfeeding evidence includes one-mother milk-level data, case reports, small infant follow-up, and a small post-cesarean trial. No randomized trial was identified that could settle naproxen's pregnancy outcomes.