The statements he makes about his characters all seem to point to him believing that women are for sex and babies. Period.

To be fair, he's sadly not alone in this amongst Doctor Who writers. Even RTD seemed to make his companions fixated on getting a man and/or marriage (Donna thankfully had a long run of not being this way, but certainly started and ended her arc in that box) and, by extension, all that entails (sex/babies/etc). It was like no woman could be strong and independent on her own, she had to either be with a man or actively trying to get one. It'll be nice to move on from that someday in Doctor Who, but it's such a widespread thing on telly, I'm not sure my hopes are high. :(