There is no way to influence gender of babies. One of the SimGurus made a comment on Reddit in a thread about baby genders. While reddit isn't an official game channel, the Gurus do post there from time to time.
This is the link to the thread and comment made by SimGuruDaniel on the subject of influencing baby genders:
http://www.reddit.com/r/thesims/comments/2gdm3t/baby_genders_in_ts4/The Mother does not have to take a pregnancy test to see if she is pregnant. After about 24 Sim hours, she will get the same notification as if she had taken the pregnancy test and her belly will pop out as well.
You also do not have to wait the full 3 hours for the mother to go through Labor. At any time after she goes into labor, you can click on the Mother and choose "Have Baby at Hospital" if you don't have a bassinet or you can click on the bassinet itself if you do own one and have the baby at home.
Looks good otherwise!
