Man-plus-woman-plus-time very often equals babies. It would be a trifle awkward having a bunch of toddlers around a Starship, and it is therefore natural to assume that some type of birth control will be required. This point has never been discussed in the series, since the censors won’t allow it. But if the subject could be discussed, the consensus is that birth control would closely parallel the military practices of today.
Birth control would be mandatory for unmarried females, voluntary for married females. In keeping with the advanced state of the medical arts as practiced aboard the Enterprise, a single, monthly* injection would be administered. A woman found to be pregnant would be given her choice of a medical discharge or rotation to a shore leave for the remainder of her pregnancy.
In the final analysis, science recognizes that the known, as well as the unknown, difficulties of pregnancy and birth in space makes the practice of birth control in some form completely necessary. The alternative would seem to be all-male or all-female crews.
*”Medical science at present states that to go beyond this point [monthly birth control injections] would risk interfering with metabolic cycles fundamental to the life-form itself.”– Stephen E. Whitfield, The Making of Star Trek, 1968 (pp. 206-207).
Little did they imagine a few decades later we’d have birth control methods that stop periods for several months.
I found this part of the book fascinating – I had no idea it has been talked about. I’m glad they realized women would need access to birth control, but also glad we never got to hear about women being forced into it unless they were married, and therefore able to have socially-sanctioned babies.