Mefenamic acid Pregnancy Warnings
Contraindicated last trimester of pregnancy
NSAIDs should be avoided at 20 weeks gestation and later
AU TGA pregnancy category: C
US FDA pregnancy category: Not assigned
Risk Summary: Nonsteroidal anti-inflammatory drugs (NSAIDs) use in pregnant women at 30 weeks gestation and later may cause premature closure of the fetal ductus arteriosus; NSAID use at 20 weeks gestation or later may cause fetal renal dysfunction leading to oligohydramnios and, in some cases, neonatal renal impairment.
Comments:
-NSAID use in pregnancy prior to 20 weeks gestation should be based on a benefit-risk assessment; some authorities recommend avoiding NSAIDs throughout pregnancy whenever possible.
-If NSAID use is necessary between 20- and 30-weeks' gestation, limit use to the lowest effective dose for the shortest duration possible; ultrasound monitoring of amniotic fluid should be considered if NSAID use extends beyond 48 hours; if oligohydramnios occurs, discontinue NSAID and treat appropriately.
-NSAID use is not recommended in women attempting to conceive as it may impair female fertility.
Oligohydramnios/Neonatal Renal Impairment:
-Published literature indicates that NSAID use at about 30 weeks of gestation and later in pregnancy may cause premature closure of the fetal ductus arteriosus.
-Published studies and postmarketing reports associate maternal NSAID use at about 20 weeks gestation or later with fetal renal dysfunction leading to oligohydramnios and potentially neonatal renal impairment. These are seen after days to weeks of treatment on average, although oligohydramnios has been infrequently reported as soon as 48 hours after NSAID initiation.
-Many amniotic fluid decreases were transient and reversible with drug cessation.
-There are a limited number of case reports of maternal NSAID use and neonatal renal dysfunction without oligohydramnios, some of which were irreversible and some required invasive procedures (e.g. exchange transfusion or dialysis).
-Limitations of postmarketing studies and case reports include lack of a control group; limited information regarding dose, duration, and timing of drug exposure; and concomitant medications. These limitations preclude establishing a reliable estimate of the risk of adverse fetal/neonatal outcomes with maternal NSAID use. Because the published safety data on neonatal outcomes involved mostly preterm infants, the generalizability of risks to the full-term infant is uncertain.
Animal studies have revealed evidence of an increased risk of miscarriage, cardiac malformation, gastroschisis, spontaneous abortion, and pre- and post-implantation loss following use of prostaglandin synthesis inhibitors in early pregnancy. Administration of nonsteroidal anti-inflammatory drugs (NSAIDs) during the third trimester of pregnancy may cause significant adverse effects, including premature closure of the fetal ductus arteriosus, pulmonary hypertension, fetal renal impairment, oligohydramnios, and inhibition of platelet aggregation. There are no controlled data in human pregnancy.
US FDA Drug Safety Communication (10-2020): The FDA is requiring a new warning be added to NSAID labeling describing the risk of fetal kidney problems that may result in low amniotic fluid. The FDA is recommending pregnant women avoid NSAID use at 20 weeks gestation or later. Through 2017, the FDA has received 35 reports of low amniotic fluid levels or kidney problems in mothers who took NSAIDs while pregnant. Five newborns died; 2 had kidney failure and confirmed low amniotic fluid, 3 had kidney failure without confirmed low amniotic fluid. The low amniotic fluid started as early as 20 weeks of pregnancy. There were 11 reports of low amniotic fluid levels during pregnancy and the fluid volume returned to normal after the NSAID was stopped. The medical literature has reported low amniotic fluid levels with use of NSAIDs for varying amounts of time, ranging from 48 hours to multiple weeks. Complications of prolonged oligohydramnios may include limb contractures and delayed lung maturation. In some postmarketing cases of impaired neonatal renal function, invasive procedures such as exchange transfusion or dialysis were required. In other cases, the condition was reversible within 3 to 6 days of stopping the NSAID and in these cases reappeared when the same NSAID was restarted.
Administration during labor and delivery is not recommended; onset of labor may be delayed and duration increased with greater bleeding tendency in mother and child.
NSAIDs may impair female fertility; withdrawal of NSAID therapy should be considered in women with difficulties conceiving or who are undergoing investigation of infertility.
AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.
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.
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