Massive missed opportunity. It would have introduced a possible new character for future Treks. Trek has always been a space adventure with strong emphasis on the characters and their relationships. A pregnant Saavik had so much new story line embedded within and a chance to develop relationships even further. It would have shown how willing Saavik was to sacrifice for Spock. It would have created a secret/relationship between she, Kirk and McCoy. It would have given Spock's parents a grandchild whom they would have wanted and gratefully raised. Yet it offered the opportunity for Spock to remain in outer space with his crew for years not knowing.
They missed many opportunities never introducing McCoy's daughter and possibly grandchildren. I also thought Kirk should have married & divorced when he had a desk job -- between the TOS and TMP era and possibly fathered a child who would not just get killed off as usual. All chances for future characters which they missed out upon.
Too soap operaish? They followed similar story lines in TNG giving Worf & Troi children -- and those characters were not nearly as popular and nobody cares about them or their love child.
The development of wonderful characters and their relationships to each other with the background of dramatic events, adventure, discovery, war etc would have added to what made ST great. Instead it went toward more of a Star Wars & battles between future fantasy groups akin to "Lord of the Rings" which gets old fast for me.