It's really perplexing that so many people seem just fine with Saavik and Spock getting married, when if you look at the interactions between Kirstie Alley and Nimoy in Wrath of Khan, the two of them display not one iota of attraction or chemistry other than professional respect.
Oh but wait, some of you might say, they are Vulcans and wouldn't the reasons for why they mate be founded in logic? Except if you look at all of the women Spock was attracted to during TOS, there was always a LOT more than logic involved (the Romulan Commander, Leila, Droxine...) Spock broke off his engagement with T'Pring because it would only have been a loveless marriage of convenience, and so one between Spock and Saavik would have been.
So why were Leonard Nimoy and Harve Bennett ok with pushing this idea forward? because despite both men being quite intelligent, they also were born in the very early 1930s, well ahead of when recognizing women as complete equals was a firm concept. Neither man seemed to even consider that Saavik wouldn't keep this hypothetical baby. Saavik was played as a very driven Starfleet cadet, with her eye on an early command (Kirk sees her as a kindred spirit since he gave her temporary command of the ship). Having a child this unexpectedly would force her to pause her military career for many years (she hadn't yet even been assigned for a first tour). The Saavik from Wrath of Khan would NOT abandon her personal ambitions because she sought to save her former commanding officer. Also, the inappropriateness of continuing a relationship with her commanding officer should be considered...
How would making Saavik pregnant with Spock's child have ruined her? Well, making her a much more nonemotional Vulcan in Trek 3 certainly damaged her appeal. In WOK, Saavik almost stole the film. In Trek 3, she's barely a blip, and so much so that she's never reappeared in almost 40 years.
Saavik was greatly appealing due to her subdued emotionalism and stealth sensuality, but also for her fearlessness (she stands up and corrects Kirk, she dives in and joins a dangerous landing party). Like it or not, we all lose a lot of our fearlessness when we become responsible for another life.
Saavik was a breakout character when Wrath of Khan was released, and likely would have replaced Spock in future Star Trek movies had Leonard Nimoy not returned for the third one and onward. But because Spock did so, Nimoy chose wrongly that she should not be more emotional than Spock, so she became a plank of wood which killed her momentum. Having her become pregnant TO Spock would have reduced her as a strong individual character and replaced her as "Spock's baby mama".