Why is my game crashing after sim gives birth?

Do you have any mods or CC (custom content)? Try taking that out.
See this for more information: [PLEASE READ] Usage of Mods and Custom Content

If that isn't the issue, could you post a DxDiag?
Please follow this how to on how to gather your DxDiag.
You can post the DxDiag by attaching it to your next reply.
Don't paste it directly into your answer, because that won't fit.