The core identity issue is threatened. And Hannah Wept by Rabbi Michael Gold which tells the story of Hannah from the Old Testament. It's exactly the same dynamic. It starts back with the games that children play. When girls play they are rehearsing all the things they need to be mothers.
Children are concrete thinkers and they're preparing for the roles they'll take as adults.
Through play, such as with tea parties and playing with dolls, girls are preparing for the mother role. Girls will huddle together and talk about what they're going to name their babies. Even tomboys generally make some time to play with dolls. We've been programmed, programmed, programmed. Men generally do not have the same response.