Ah, a Leave of Absence...
While I don't think a mother has time to complete a manuscript, I do think she can take advantage of any extra time she might have.
My little cutie is at the 2-month mark, and we've established The Baby Whisperer's routine of Eat-Activity-Sleep-You time (E.A.S.Y.), and I've found myself with at least 4 hours/day of free time. The baby is asleep, so I have time to check my e-mail, surf the web, play a computer game, watch a Netflix movie, talk with my husband. Granted, not all of those things get done in one day, but there is quite a lot more time than I thought I'd have.
Anyway, all this to say that I am glad I work for a Fortune 500 company and am allowed 18 weeks of maternity leave. What a blessing!