But it may prevent you from going to jail!!
No, it doesn't keep you from going to jail, although it did once upon a time. Something like 4000 pregnant women are arrested and jailed awaiting trial each year. Each state, or most every state (I'm unaware of any that don't), has established "Minimum Jail Standards" which require the medical treatment units within each jail system to provide for treatment of pregnant inmates. That's not to say that the cop on the street or even a judge won't cut somebody some slack if their pregnancy is advanced, but from what I've seen that is much more likely to occur in cases of misdemeanors and low-level, non-violent felonies.