Aborting Babies with Possible/Definite Health Implications

Abortion is an increasingly prevalent, yet taboo topic. Aside from the political aspect of aborting a fetus, there are halachic questions that arise as well when the health of a fetus is at risk. The basic premise in Judaism is that we do not permit unnecessary abortions- there must be a reason for one, and even then, the laws are quite stringent as there is a significant value to human life. Furthermore, the question arises of up until what stage of gestation should abortion be permitted under these circumstances?

The punishments for gentiles and Jews, respectively, for killing an unborn fetus:
For gentiles, the law seems much more strict, that killing an uborn fetus constitutes as a capital offense. This is found in bereishis 9:6-

This phrase can be interpreted as killing a person inside another person, like a fetus. The torah writes this as a capital offense for non-Jews since this was a law stated before the giving of the torah, and this idea is restrengthened in Sanhedrin 72b as well-

However this law does not seem to be applied to Jews...

How would this make sense that the capital offense of abortion constituting murder would not apply to Jews?

The Tosfos answers this question generally that commandments for gentiles apply for Jews as well, so this clarification gets rid of the assumption that the torah is more lenient with abortion with Jews. With this concept in place, how can this rule help form the rules for whether or not a woman can get an abortion if the child will be at a disadvantage in terms of its health?

The halachah considers the fetus and its mother as one entity as the baby is dependent on the mother, and this idea is sourced in a mishna in maseches arachin-

The reasoning the mother is killed without waiting for the baby is because the baby is connected to the mother's body and is dependent on the mother. The death sentence put upon the mother thus applies to the fetus as well. This halacha suggests the idea that there may be scenarios where terminating a pregnancy is allowed, such as with a mother diagnosed with zika is in essence placing the same potentially detrimental sentence on the developing fetus. This analysis further allows for the question of when would potential abortions be permitted until?

Ramban brings up an essential point that an embryo does not have a life up until forty days after conception-

As shown in the source, despite the fact that the embryo is not considered alive, one can still desecrate Shabbos to save it. This shows the value of potential human life, that one should not abort fetuses frivolously and take advantage of this Halacha. However, if necessary, such as in cases where a baby is at high risk or is diagnosed with a disease such as tay-sachs or zika, one may abort up until 40 days after conception. If one passes the 40 day mark, they should not abort, even if there is a probability of a serious fetal illness, since there are orphanages and foster homes to take care of a baby in such a scenario. Human life is extremely valuable and we should treat it like such.