The legal standard whereby a person can be convicted of double homicide on a pregnant woman is after 24 weeks of gestation. There are two reasons that fetuses of 24 weeks gestation are given this status. There is a chance of survival outside of the womb and fully functioning brain wave activity. I think that a woman has had 24 weeks to make a choice to terminate a pregnancy and to wait til after the 24th weeks is murder. Otherwise the penalties for causing a woman to terminate a 24 week plus pregnancy due to an assault could no longer be considered murder.
This is why I voted for right to free exit at the closest answer to 24 weeks which was 6 months when technically it is considered 5 months. Not every month of pregnancy consists of 4 weeks. The total gestation is 40 weeks which would be 10 months if the months consisted of even 4 week intervals.
I will be very happy when technology is advanced enough to keep all unwanted fetuses alive and healthy so they can be adopted.
The chances of survival outside of the womb are not a valid criteria for determining whether a child is a person. Advances in medical technology do not suddenly change your status as a person.
Once the embryo becomes a fetus (about three months) it has a functioning nervous system. The idea of "a fully functioning nervous system" is misleading. Nervous development continues throughout life.
Arguments about whether a child with a newly functioning nervous system is a person are fine for speculative scientific and philosophical discussions, but should not be used as a rationalization for murder. E.g., you may not know whether an unconscious person is alive or dead, but shooting him in the head without cause is still murder.
The mother's body is also part of the child's body until it can live separately from it. That includes the period of time that the child is dependent on his mother's milk unless a substitute for the milk or a substitute for the mother can be found.
Late abortion, infanticide and death from child neglect are all moral grounds for a murder charge.