My prior assistant was with me for three years when she had her second child - she had some PTO that she used up, and the rest was unpaid. The baby was born in Sept, so she took off all of Sept and Oct, and worked part-time for the rest of the year, and went back to full-time in Jan.
We're a two-person shop, so I was flying solo for a while. She was a great employee who only left for family reasons.