Women who are opioid dependent are stabilized on buprenorphine (Subutex) for the remainder of their pregnancy. This is based the following national treatment guideline which is endorsed both by the American College of Obstetrics and Gynecology (ACOG) and by the American Society of Addiction Medicine (ASAM).
"Decisions to use opioid agonist medications in pregnant women with opioid use disorder revolve around balancing the risks and benefits to maternal and infant health. Opioid agonist treatment is thought to have minimal long-term developmental impacts on children relative to harms resulting from maternal use of heroin and prescription opioids. Therefore, women with opioid use disorder who are not in treatment should be encouraged to start opioid agonist therapy with methadone or buprenorphine monotherapy (without naloxone) as early in pregnancy as possible. Furthermore, pregnant women who are on agonist therapy should be encouraged not to discontinue therapy while pregnant."
"Pregnant women who are physically dependent on opioids should receive treatment using agonist medications rather than withdrawal management or abstinence as these approaches may pose risk to the fetus. Furthermore, withdrawal management has been found to be inferior in effectiveness over pharmacotherapy with opioid agonists and increases the risk of relapse without fetal or maternal benefit."
ASAM National Practice Guideline May 27, 2015