I guess biological reproduction and the moral implications thereof did not cross Ayn Rands mind at the time. Either that, or children are somehow exempt from objectivism, which begs the question of how or when to distinguish between child and adult.
Then again, I only read Atlas Shrugged, and maybe Ayn Rand expressed her thoughts on the subject elsewhere.
The recaptured sense of her [Dagny's] own childhood kept coming back to her whenever she met the two sons of the young woman who owned the bakery shop. . . . They did not have the look she had seen in the children of the outer world--a look of fear, half- secretive, half-sneering, the look of a child's defense against an adult, the look of a being in the process of discovering that he is hearing lies and of learning to feel hatred. The two boys had the open, joyous, friendly confidence of kittens who do not expect to get hurt, they had an innocently natural, non-boastful sense of their own value and as innocent a trust in any stranger's ability to recognize it, they had the eager curiosity that would venture anywhere with the certainty that life held nothing unworthy of or closed to discovery, and they looked as if, should they encounter malevolence, they would reject it contemptuously, not as dangerous, but as stupid, they would not accept it in bruised resignation as the law of existence.If children were still considered chattel possessions that could be bought and sold they'd probably have a higher view of childbearing.