WASHINGTON — This baby was truly a surprise.

Katherine Kropas hadn’t missed a day of work in two years, but when she visited the hospital for the strange and sudden pain in her stomach and back, she discovered that she was pregnant and in labor.

An hour later Kropas, 23, had a baby girl.

“I thought I had put on some Christmas season weight, but I never thought I was pregnant. Never,” she tells WCVB in Boston.

Kropas says she was on birth control, had a menstrual cycle and didn’t have morning sickness.

Surprise pregnancies, that are known as “cryptic” pregnancies, are more common that you may realize, although they are still rare.

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