It is neither the shape of our meat nor the code of our genetics that make us a human being but the unique nature of our sentience. This sentience does not exist in the womb nor even for a short time after birth before an infant has been exposed to enough stimulation and human interaction to begin to form an awareness of self or other.
The question of "when does life begin?" is a red herring; life began millions of years ago and continues uninterrupted in the process of reproduction. "Life" does not take a holiday when gametes join together for some later stage of development.
A fetus (and newborn infants up to a certain age by the standards of many previous and some current societies including the forebears of Western Civilization - the Greeks and Romans) is a potential human from the standpoint of sentience. Traditional people and our own ancestors are and were not so materialistic as to assume that a human shaped body in any way defined "humanity". Nor if they had been aware of genetics would they have necessarily assumed that human genetics make a human being, any more than an acorn is an oak tree.
The unique aversion to abortion by Christianity as a religion comes down to a dogma that it is a sin to prevent any lump of phlegm, bile, and blood that can develop to eventually accept or reject "Jesus as Savior" from achieving it's divine destiny. In Baptismal vows the parents and Godparents even promise to ensure that the infant grows up to make the "right choice". When you terminate a pregnancy you are stealing potential souls from Jesus and the Church is what it all ultimately comes down to.
Societies not dominated by this implicit understanding of the meaning of life are much more practical and rational in deciding matters of who grows up and who does not in terms of sentience, degree of dependency, available resources, and the survival contingencies of the already developed human members of the community.
Somewhere between the Roman Paterfamilias and his absolute power of life and death over all dependents regardless of age, and the modern insanity at the other extreme of demanding that every fertilized egg be understood as having a "right" to develop even at the expense of pre-existing human beings, is a standard based on Reason (in the Classical sense).
In that standard from reason is a consideration that existing human beings must be free to plan for the future of their own and their community's survival and fitness, in terms of available resources, current size of the group, and other matters that are obvious to indigenous people but civilized affluent people take for granted and Christian civilization completely ignores or rejects as abhorrent on purely emotional and dogmatic grounds.
The decision to make or keep a baby can be and should be as rational a decision as whether or not to breed or keep a puppy, horse, pig, or cow - who are extremely valued members of a traditional village family by the way - or to give it away or put it down -- and based on the same logical and rational considerations of practicality (This is reflected in ancient Greek in that a baby is always called an "it" and not a he or she.) Is there space for it? Can we feed it and provide for it's needs and our own as current members of the tribe? Will it strengthen us or weaken us? Do I already have a baby and can't carry two and outrun jaguars or tigers at the same time? Or should we send it "back" to the spirit world of the ancestors to incarnate some other time in some other place that is more convenient and better suited to its thriving?
Family planning is not a matter for a "government" to intrude upon in my opinion. And on a related note and conversely neither do I feel that a lack of family planning on someone else's part puts any moral claim upon my own resources to support someone else's small human-shaped meat puppets.
A truly free people must be free to limit their own population and live within their means. Any lower standard of freedom devolves into an unsustainable insanity. And those who decide not to plan for the future should face the consequences of their actions or inactions as a family or small consenting community; if they really cared for children they would not have brought them into the world in the first place, or would have ended their existence prior to their achieving sentience, if they lack the means to support them.
This includes young with deformities or conditions requiring extraordinary expense and care - normal healthy children who will grow up to be strong with a likelihood to outlive their parents and care for them in old age is one thing, and that is a challenge enough for the average working couple. A sickly or defective child who will only live a short painful life and bankrupt a family in the process is done no favor by a society who is not willing to confess it is okay to tell God - "Thank you Lord but we are sending this one back to the Manufacturer. Please let's try again."
If these decisions are "agonizing" to parents today it is only because of the moral milieu that insures that any such notion instills maximum guilt and self loathing even for considering it, with a "Life At Any Cost" mantra at the heart of all decisions, medical in particular (or rather, a pulse at any cost, not necessarily much of a Life), but in other times and places would be recognized as the rational and even moral response in the most classical sense of the word - creating the greatest good for all concerned in terms of actual lives lived on Earth, not an abstract idealistic standard outside of any context or reality of real people with real limitations in Matter and Form. This is something any bear or cat or mouse or even a chimpanzee mother knows instinctively - if a newborn young won't survive to live a normal life or there is not enough food etc. to go around, Mom recycles and brings back to herself.
It is the nature of the Ancestral world to try to keep pushing souls into this one regardless of how broken the vessels, but as the Princes of Earth we are the Gatekeepers of souls and must exercise our power to say No Thank You sometimes both on behalf of the souls trying to enter and those already fully established and formed in this plane as sentient humans, both children and grown adults. This is the responsibility we took on in eating from the Tree of Knowledge, and our nature as creations in God's image; and it was only with this knowledge that Eve's Gate was opened, and the river of souls began to flow between Her Divine Thighs.
May She guard and keep Her Gate diligently and intelligently with true Wisdom, Mercy and Compassion for all.