Two cases of acetaminophen overdose in late pregnancy have been reported. In both cases neither the neonate nor the mother suffered hepatic toxicity.

Investigations have revealed conflicting results with regards to the pharmacokinetic disposition of acetaminophen in pregnant women. One study has suggested that the oral clearance of acetaminophen is 58% higher and the elimination half-life is 28% longer in pregnant women compared to nonpregnant women. Another study has suggested that the elimination half-life is not different in patients who are pregnant. That study also suggested that the volume of distribution of acetaminophen may be higher in pregnant women.

One study has suggested that acetaminophen in typical oral doses may result in a reduced production of prostacyclin in pregnant women. That study also suggested that acetaminophen does not affect thromboxane production.

In a study of 2817 fertile women, no evidence of adverse effects from caffeine was found. The fecundability ratio (adjusted for known risk factors for time to conceive) was 1.03 between fertile women who consumed more than 7000 mg caffeine per month and those who consumed 500 mg or less per month. Furthermore, caffeine was not associated with infertility in 1818 infertile women and their primiparous controls. In another study (n=441) no evidence was found that moderate caffeine use increased the risk of spontaneous abortion, intrauterine growth retardation, or microcephaly.

One study (n=18,478) on the consumption of coffee (with caffeine regarded as the key component in studies of the potential effects of coffee) found that pregnant women who drank 8 or more cups of coffee a day had more than twice the risk of delivering a stillbirth compared with women who did not drink coffee during pregnancy. However, as one letter regarding this study states, the "article raises more issues than it settles" including how much of increase in stillbirths was actually due to the increase in caffeine consumption. Another letter responding to this study claims that consumption of 8 or more cups of coffee is suggestive of addictive behavior. Those with addictive behavior are more likely to be smokers, have a high intake of alcohol, and use illegal drugs. Other questions regarding this study were also raised. Therefore, it has been questioned if the increased risk of delivering a stillbirth that the study associated with consumption of 8 or more cups of coffee per day can be associated with increased risk from increased caffeine consumption.

Acetaminophen has not been formally assigned to a pregnancy category by the FDA. It is routinely used for short-term pain relief and fever in all stages of pregnancy. Acetaminophen is believed to be safe in pregnancy when used intermittently for short durations.

The drug caffeine in general has not been formally assigned to pregnancy category by the FDA. (However, caffeine citrate injection has been assigned to pregnancy category C.) Both human and animal studies have failed to reveal evidence of significant mutagenic or carcinogenic effects. Caffeine crosses the placenta. Fetal blood and tissue levels in the fetus have been similar to those in the mother. One case of maternal caffeine-induced hypokalemic paralysis has been reported. Caffeine has been reported to be an animal teratogen only 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 their intake of caffeine to a minimum.

Isometheptene has not been formally assigned to a pregnancy category by the FDA. Animal studies have not been reported. There are no controlled data in human pregnancy.

Acetaminophen/caffeine/isometheptene mucate should only be given during pregnancy when need has been clearly established.

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One small study on acetaminophen has reported that following a 1000 mg dose of acetaminophen to nursing mothers, nursing infants receive less than 1.85% of the weight-adjusted maternal oral dose.

Acetaminophen is excreted into human milk in small concentrations. One case of a rash has been reported in a nursing infant. Acetaminophen is considered compatible with breast-feeding by the American Academy of Pediatrics.

Caffeine is excreted into human milk in small amounts. Adverse effects in the nursing infant are unlikely. However, irritability and poor sleep patterns have been reported in nursing infants. The amount of caffeine generally found in caffeinated beverages is considered to usually be compatible with breast-feeding by the American Academy of Pediatrics. Because caffeine is excreted into human milk and because caffeine is metabolized slowly by nursing infants, consumption of more than moderate levels of caffeine by nursing mothers is not recommended.

There are no data on the excretion of isometheptene into human milk.

See references