Pregnant Maid

A husband and his wife advertised for a live-in maid to cook and do the housework. A likely-looking girl came in from the country and they hired her. She worked out fine, was a good cook, was polite, and kept the house neat.
One day, after about six months, she came in and said she would have to quit. "But why?", asked the disappointed wife.  She hemmed and hawed and said she didn't want to say, but the wife was persistent, so finally she said, "Well, on my day off a couple of months ago I met this good-looking fellow from over in the next county, and well, I'm pregnant." 
The wife said, "Look, we don't want to lose you. My husband and I don't have any children and we'll adopt your baby if you will stay."  She talked to her husband and he agreed.  So the maid said she would stay. The baby came, they adopted it and all went well. 
After several months though, the maid came in again and said that she would have to quit. The wife questioned her, found out that she was pregnant again, talked to her husband, and offered to adopt the baby if she would stay. She agreed, had the baby, they adopted it, and life went on as usual once again.  In a few months, however, she again said she would have to leave. Same thing. She was pregnant. They made the same offer, she agreed, and they adopted the third baby.
This time she worked for a week or two, but then said, "I am definitely leaving for good now."  "Don't tell me you're pregnant again?" asked the lady of the house. "No," she said, "there are just too many kids here to pick up after!"