### Risk Summary

There are limited available data with formoterol fumarate inhalation solution use in pregnant women to inform a drug-associated risk of adverse developmental outcomes. Beta-agonists may interfere with uterine contractility (see Clinical Considerations). In animal reproduction studies, oral administration of formoterol fumarate to pregnant rats and rabbits caused increased fetal malformations (rats and rabbits), decreased fetal weight (rats), and increased neonatal mortality (rats) following administration of doses that produced exposures approximately 730 to 29,000 times the MRHD on a mg/m2 or AUC basis. These adverse effects generally occurred at large multiples of the MRHD when formoterol fumarate was administered by the oral route to achieve high systemic exposures. No effects were observed in a study with rats that received formoterol fumarate by the inhalation route at an exposure approximately 300 times the MRHD (see Data). 

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. 

### Clinical Considerations

Labor or delivery

There are no adequate and well-controlled human studies that have studied the effects of formoterol fumarate inhalation solution during labor and delivery. Because of the potential for beta-agonists interference with uterine contractility, use of formoterol fumarate inhalation solution during labor should be restricted to those patients in whom the benefits clearly outweigh the risk. 

### Data

Animal Data 

In embryofetal development studies with pregnant rats and rabbits dosed throughout the period of organogenesis, formoterol fumarate did not cause malformations in either species. However, for pregnant rats dosed throughout organogenesis, formoterol fumarate caused delayed fetal ossification at an exposure approximately 50 times the MRHD (on a mcg/m2 basis with maternal oral doses of 200 mcg/kg and higher) and decreased fetal weight at an exposure approximately 1,500 times the MRHD (on a mcg/m2 basis with maternal oral doses of 6,000 mcg/kg and above). In a pre- and post-natal development study with rats dosed during the late stage of pregnancy, formoterol fumarate caused stillbirth and neonatal mortality at an exposure approximately 1,500 times the MRHD (on a mcg/m2 basis with maternal oral doses of 6,000 mcg/kg and above). However, no effects were observed in this study at an exposure approximately 50 times the MRHD (on a mcg/m2 basis with a maternal oral dose of 200 mcg/kg). 

In embryofetal development studies, conducted by another testing laboratory, with pregnant rats and rabbits dosed throughout the period of organogenesis, formoterol fumarate was teratogenic in both species. Umbilical hernia, a malformation, was observed in rat fetuses at exposures approximately 730 times the MRHD (on a mcg/m2 basis with maternal oral doses of 3,000 mcg/kg/day and above). Brachygnathia, a skeletal malformation, was observed in rat fetuses at an exposure approximately 3,600 times the MRHD (on a mcg/m2 basis with a maternal oral dose of 15,000 mcg/kg/day). In another study with rats, no teratogenic effects were observed with exposures up to approximately 300 times the MRHD (on a mcg/m2basis with a maternal inhalation dose of 1,200 mcg/kg/day). Subcapsular cysts on the liver were observed in rabbit fetuses at an exposure approximately 29,000 times the MRHD (on a mcg/m2 basis with a maternal oral dose of 60,000 mcg/kg/day). No teratogenic effects were observed with exposures up to approximately 1,700 times the MRHD (on a mcg/m2 basis with a maternal oral dose of 3,500 mcg/kg).