Just add it as a Radio button options. You can even select female by default. 

**It takes very little cognitive overhead and time for everyone to select the correct value!**

Keep selecting the correct gender only one click away.

If you're afraid that there would be some serious exceptions in you're target demographic or a lot of people that don't want to add the information you can add a third option unspecified and set that as the default value.

Asking for a **Title** adds a big overhead to the one selecting the correct value.

I would also add what the information is actually used for. (or what its not used for eg. no gender targeted advertisment)

You can also add other ways to detect gender. Adding it as a survey question or simply letting sales representatives update the information after phone calls chould fill out the blanks pretty fast.