If there is a transmissible disease like HIV-positive or hepatitis C virus infection, the infection of the healthy partner and the unborn child has to be protected.
If the male partner has this kind of diseases, the sperm will be prepared so that no virus can be transmitted to the woman or ovum. If the female partner is infected, treatment with drugs over the period of the pregnancy is conducted, the child is inoculated and a Caesarian delivery induced. Like with all medical procedures, there can be no 100 per cent certainty, that partner or child not get infected. Albeit the risk is nominal!