Well, maybe we should set up a hotline like we do with child abuse so neighbors can report their neighbors or friends for drinking/smoking/getting high while pregnant. How far would we go? Certain STDs can also be harmful to the fetus, so clearly we'd have to prohibit promiscuous sex by the mother. Should she be allowed to work? Or would she have to submit a doctor's note to state that working is allowed?
Yes, this all gets ridiculously tricky when you're clearly reaching and trying to say things that are relatively common sense when compared to a current situation but would not give you ammunition for your rhetoric.
For example...
Why would you need a way to report potential abuse any different than what's currently there with Child Protective Services. If you see your neighbor drinking nightly and screaming at his kids you can report it. What's different about seeing them down a bottle of jack while 8 months pregnant?
Working could theoritically dangerous to children who are born because that can cause stress on the mother and takes time away from the children thus possibly making her less likely to be alert to a potential danger such as a kid falling in the pool otu back. Yet we don't require doctors notes to allow women to work then. At most, you could potentially look at a law requiring pregnancy time off to be given after "X" amount of months but even that wouldn't be entirely needed and its not like there isn't laws in place now to allow pregnant wome nto take time off when/if need be.
Further the attempt to compare these things to that of abortion is ludicrous in and of itself. There is a large difference between taking actions that may potentially, in some cases in a VERY off shot (like promiscuous sex), and takin an action that is 100%, without question, damaging to the fetus.
We don't actively monitor or have extremely detailed laws about a LOT of things that can harm, do damage, or even lead to the deaths of our BORN children. Outside of beating your children or actually killing them most of it is based on reports and then investigations into mistreatment. The general assumption with the government dealing with Children is that you're going to be taking care of them unless there is reason present to make the government believe otherwise. Actively going to a clinic and saying "Give me an abortion" would be such type of a reason in this hypothetical. Your neighbor seeing you punching your stomach and downing a fifth of jack and calling in would be a reason. Simply being pregnant is not a reason for the Government to actively believe you're going to mistreat the child anymore than simply having a born child is reason for the government to actively believe it.
The practical realm only presents this big of a problem is if you refuse to be anything but obtsue about the situation and apply simple logic and common sense that much of the same rules that apply to children now could apply then. Abortion would be much like the current laws now which, you know, say you can't go and chop your kids head off.
There would be no reason to extend them greater protection than is afforded other children in this hypothetical situation.