Aspirin inhibits prostaglandin synthesis. When given late in pregnancy, it may cause premature closure of the fetal ductus arteriosus, and delay labour and birth. Aspirin increases the bleeding time in the newborn and in the mother because of its antiplatelet effects. Low-dose aspirin (100 mg/day) does not affect bleeding time. High-dose aspirin (2 g per day) has been associated with stillbirths, cerebral hemorrhage, oculoauriculovertebral dysplasia, neonatal salicylate toxicity, constricted ductus arteriosus, cyclopia, and neonatal acidosis. Some cases of congenital heart defects have been reported. The American College of Obstetricians and Gynecologists and the US Preventative Services Task Force support the use of low-dose aspirin prophylaxis in women at high-risk of preeclampsia.

Caffeine crosses the placenta. Fetal blood and tissue levels in the fetus are similar to those in the mother. Caffeine has been reported to be an animal teratogen with doses high enough to cause toxicity in the mother. In 1980, the Food and Drug Administration issued an advisory (based primarily on animal evidence) which stated that pregnant women should limit intake of caffeine to a minimum. The American College of Obstetricians and Gynecologists feel a definitive relationship of high caffeine intake and miscarriage cannot be determined, moderate caffeine consumption (less than 200 mg total per day) does not appear to be a contributing factor in miscarriage or preterm birth. There are no controlled data in combined use of this drug in human pregnancy.

US FDA pregnancy category: Not formally assigned to a pregnancy category due to product being available over-the-counter. Over-the-counter warning: It is especially important not to use aspirin during the last 3 months of pregnancy unless definitely directed to do so by a doctor because it may cause problems in the unborn child or complications during delivery.

Avoid use during the first two trimesters of pregnancy unless the benefit outweighs risk to the fetus; not recommended during the third trimester of pregnancy

US FDA pregnancy category: Not formally assigned to a pregnancy category

Comments:
-Aspirin: Chronic or intermittent high doses should be avoided, especially during the third trimester of pregnancy.
-Caffeine: Conflicting data exits as to whether there is a correlation with high caffeine intake and miscarriage; moderate consumption (less than 200 mg/day) does not appear to contribute to miscarriage or preterm birth.

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Aspirin is rapidly metabolized to salicylate after ingestion; salicylic acid is excreted into human milk. Metabolic acidosis has been reported in one breastfed infant following long-term, high-dose maternal aspirin ingestion. Regular/high doses of maternal aspirin could impair platelet function in the breastfed infant. Reye's syndrome is associated with aspirin use in infants with viral infections, but the risk from salicylate in breastmilk is unknown. Daily low-dose aspirin (75 to 325 mg per day) has yielded low salicylate levels in breastmilk and some experts suggest low dose aspirin may be considered for antiplatelet therapy in breastfeeding women.

Caffeine is excreted into human milk; there is insufficient data to quantify a safe maternal caffeine dose while breastfeeding. Fussiness, jitteriness and poor sleep patterns have been reported in infants of mothers with very high caffeine intake (about 10 or more cups of coffee daily) while studies in mothers taking half that (5 cups of coffee daily) found no stimulation in breastfed infants 3 weeks or older. Preterm and younger newborns metabolize caffeine slowly so a lower intake in mothers of these infants is preferable. A coffee intake of more than 450 mL per day may decrease breastmilk iron concentrations and result in mild iron deficiency anemia in some breastfed infants.

Benefit should outweigh risk

Excreted into human milk: Yes

Comments:
-Alternative analgesic and antipyretic therapy should be considered, especially when nursing younger infants

See references