Is it safe for a pregnant woman to take gabapentin to try and get over the withdrawals from heroin.?

No: You need to check with an addictionologist to find out what your options are.

No: It's nor recommended to take Gabapentin during the pregnancy. Furthermore, it's not the medication for heroin withdrawal.

Other much safer way: Heroin is hard habit to kick especially in a hurry such is your condition of pregnancy. I would recommend a speciality Methadone clinic which specializes in pregnant women. Gabapentine has more problems than its worth during pregnancy on fetus and its not for withdrawal from heroin any way.