Introduction Current WHO guidelines recommend using methadone or buprenorphine as maintenance treatments for maternal opioid use disorder. However, buprenorphine‐naloxone, with a lower abuse risk than buprenorphine monotherapy or methadone, offers a potentially beneficial alternative, but scientific evidence on its effects on pregnancies, fetuses, and newborns is scarce. This paper compares the outcomes of the pregnancies, deliveries, and newborns of women on buprenorphine‐naloxone, buprenorphine, or methadone maintenance treatments. According to the hypothesis, as a maintenance treatment, buprenorphine‐naloxone does not have more adverse effects than buprenorphine, whereas methadone is more complicated. Material and methods In this population‐based study, 172 pregnant women on medical‐assisted treatments were followed‐up at Helsinki University Women's Hospital (Finland). Women receiving the same opioid maintenance treatment from conception to delivery and their newborns were included. Consequently, 67 mother–child dyads met the final inclusion criteria. They were divided into three groups based on their opioid pharmacotherapy. The outcomes were compared among the groups and, where applicable, with the Finnish population. Results The buprenorphine‐naloxone and buprenorphine groups showed similar outcomes and did not significantly differ from each other in terms of maternal health during pregnancies, deliveries, or newborns. Illicit drug use during the pregnancy was common in all groups, but in the methadone group it was most common (p = 0.001). Most neonates (96%) were born full‐term with good Apgar scores. They were of relatively small birth size, with those in the methadone group tending to be the smallest. Of the neonates 63% needed pharmacological treatment for neonatal opioid withdrawal syndrome. The need was lower in the buprenorphine‐based groups than in the methadone group (p = 0.029). Conclusions Buprenorphine‐naloxone seems to be as safe for pharmacotherapy for maternal opioid use disorder as buprenorphine monotherapy for both mother and newborn. Hence it could be a choice for oral opioid maintenance treatment during pregnancy, but larger studies are needed before changing the official recommendations. Women on methadone treatment carry multifactorial risks and require particularly cautious follow up. Furthermore, illicit drug use is common in all treatment groups and needs to be considered for all patients with opioid use disorder.