The cultural mandate requires humans to reproduce, and the procreative tendency serves this end.
"An indissoluble link [joins] the significances of unity and of procreation ... in the conjugal act. ... An act ... which impairs the capacity to transmit life ... resists the design ... of the author of life. ... Once the generative process has begun, its direct interruption is to be absolutely rejected, [as is] any action ... that is specifically intended to prevent procreation."
Giovanni Battista Montini ("Pope Paul 6"), Humanae Vitae (1968), 12-14.
"Thou shalt not kill". Or, more generally: Harm not the proper cycle of human life, rising when the unitive-procreative motive leads a man to impregnate his wife, and setting peacefully in the evening of years.
To some, the weight Humanae Vitae places on the words "direct" and "specifically" may seem absurd. "If the intended outcome is the same", they may ask, "what matter how it is done?" To such a mind, to which civilian casualties seem no better than terrorism, abstinence likewise seems no better than spermicide.
But that approach is simplistic. The idea that only results matter is as absurd as the idea that only what can be proved is worthy of belief, and for similar reasons: if I do A in order to achieve B, why should I want to achieve B? And if B is in its turn a means to the end of C, why C, and where does the chain end: what is the ultimate good sought? (More pleasure? Less pain? Both? Perhaps the pampered pet on the hearthrug is your model, or the wool-sheep in the field. A just society? You mean that the aim of your Consequentialism is a society where folk are not ... Consequentialist?)
Everywhere we encounter the incommensurable demands of spontaneous virtue (the immediate, ready-to-hand good) and of calculating utility (the remote, planned good), and neither of these rivals should be allowed to swamp the other. Virtue holds its ground, carrying its should with it.
There are of course exceptions. In rare emergencies, it is just to kill, abort or contraceive.
If the infant were developed enough for a self to have incepted, we would need to assume that it had done so, in which case abortion would be homicide, and the emergency would need to be even graver. However, my guess is that inception never precedes the start of the post-natal brain-growth spurt, so I assume this case never occurs. (Most discussions of "late abortion" focus on physiological "viability", which is a different question, and an irrelevant one.)
Back to Every man is king of his family.