What are the effects of heroin on a fetus in the first trimester?

Stillbirth . Heroin use in pregnancy can have serious effects on babies. The stillbirth risk is increased as well as the risk of poor fetal growth. In addition, the baby becomes addicted as well and with have to go through detoxification after delivery. Heroin uses will need to seek professional help and transition to Methadone maintenance. Some patients can undergo detox but need to be carefully monitored.
Difficult to say. Heroin use in the first trimester will either cause a full miscarriage or have minimal effects at all. This is essentially true of all toxic exposures in the first trimester that tend to kill the baby or not affect it at all. Heroin use for the rest of the pregnancy will likely cause addiction in the baby, stunted growth and increase risk of infections such as hepatitis, hiv, syphilis.