Naltrexone Use in Pregnancy

Fetal Outcomes and Safety

The Society for Maternal-Fetal Medicine, ACOG, and American Society of Addiction Medicine joint 2019 workshop report states that "data are insufficient" regarding naltrexone use during pregnancy, highlighting the need for further research 1, 2, 3, 4
Early pregnancy loss risk is associated with yolk sac diameter greater than 6 mm, and maternal factors such as advanced maternal age and poorly controlled diabetes may also contribute to enlarged yolk sac 1
Aneuploidy and chromosomal abnormalities are the most common pathologic cause of enlarged yolk sac, and idiopathic findings may resolve or represent normal variation 3

The American College of Obstetricians and Gynecologists recommends correlating yolk sac diameter with crown-rump length and fetal cardiac activity, and considering genetic counseling if yolk sac is greater than 6 mm with other concerning features 3
The risk of stopping Low-Dose Naltrexone (LDN) depends on the underlying condition being treated, and the benefits of continuing LDN should be weighed against the unknown fetal risks 3
First trimester exposure to LDN should be minimized when possible, as this is the period of organogenesis, according to the American Journal of Obstetrics and Gynecology 1

The American Society of Addiction Medicine recommends that patients should not continue LDN without informed consent acknowledging the lack of pregnancy safety data 3
The Society for Maternal-Fetal Medicine advises against extrapolating standard-dose naltrexone data directly to low-dose formulations without acknowledging this limitation 3

The American College of Obstetricians and Gynecologists, the Society for Maternal-Fetal Medicine, and the American Society of Addiction Medicine recommend that naltrexone should not be initiated during pregnancy for opioid use disorder, but may be continued in women already taking it after careful risk-benefit assessment and informed consent, with a strength of evidence considered insufficient to support initiation during pregnancy 5

The Society for Maternal-Fetal Medicine, ACOG, and American Society of Addiction Medicine joint workshop explicitly states that data are insufficient to support the initiation of naltrexone therapy during pregnancy, and instead recommend offering methadone or buprenorphine, which are considered safe throughout all trimesters for OUD treatment 5

The American Medical Association, as reported in JAMA, advises that the naltrexone-bupropion combination, used for obesity management, should not be used during pregnancy or lactation, and women of reproductive age should use effective contraception 6