Question about employee and pregnancy?

I have a small ranch and have a couple that work for me. She works 12 hours a week feeding and cleaning up after animals, he works 8 hours a week cutting weeds, mowing keeping the place looking nice. They live on the property in a nice mobile home and their work is in exchange for rent. She is 7 months pregnant. I have told them they don't have to move. They were very worried I was going to fire them.
My question is: What would be a fair arrangement. Have him pick up her work? Have them pay for hours not worked? Should I give her some time off to have the baby? How much time do I need to give her before expecting her to work. The work is physical but not hard. She also has another job at a day care.

My husband and I also both work full time and don't have time to do her work.

Any ideas would be appreciated.

Thanks.
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The Family Leave and Maternity Act (which you are not subject to due to both the size of your ranch and the fact that your employee works less than 25 hours per week) provides some guidelines.

The key elements are:

1) Your employee is entitled to 12 weeks of unpaid leave
2) At the end of 12 weeks you must offer the employee either the same job or a comparable job at the same level of pay.

If I were you I would ask the father-to-be to pick up the slack and do whatever his wife will be unable to do.

Hope this helps
Jerry-the-bookkeeper