Hello Jocelym, I can understand your concern and feel sorry for your situation. Heroin addiction during pregnancy is really dangerous for the mother along with the baby and it should have been quit in early stage of pregnancy or before planning pregnancy. However, there is no other way for you but to accept the circumstances and be prepared for the possible consequences as you have already planned. Heroin addiction of mother makes the fetus addicted to heroin while in womb presenting as Neonatal Abstinence Syndrome (NAS) after birth. It may cause excessive crying, seizures, low birth weight and slow weight gain, diarrhea, vomiting, fever etc. The neonates require hospitalization and treatment with Morphine which is gradually tapered off to make the newborn de-addicted to heroin. The syndrome can be diagnosed in the neonate during the primary examination by the doctor. You should let the doctors know about the history of mother s addiction so they can be ready for possible complications in mother and in the child. It is hard to say how much heroin will be detected in the baby s blood and for how long will it stay in the system as the level of mother s addiction and length of addiction period is not known. I would advise you to seek urgent rehabilitation care for your sister so that the harm that is undone yet can be prevented and she and baby can be in good health as soon as possible. I hope this information helps. Thank you for choosing HealthcareMagic. I wish mother and baby good health! Best, Dr. Viraj Shah