Would dinking alcohol heavily during pregnancy be considered by a doctor to perfom a medically necessary abortion at 18 weeks, so that insurance would cover the procedure

No, not my insurance company. What does the DOCTOR say about the medical necessity?

If this were true everyone who wanted an abortion would claim to be a heavy drinker.

I have seen women charged criminally for abusing their bodies during pregnancy and causing harm to the child - where are you?

Ummm... NO!! Doing that only causes harm to the fetus and could have a baby born with fetal alcohol syndrome... some moms go to jail for abusing their bodies while pregnant.

would dinking alcohol heavily during pregnancy be considered by a doctor to perfom a medically neccessary abortion at 18 weeks, so that insurance would cover the procedure

No, it would not be considered a medical reason for an abortion.