40 weeks = 9 months?

Typically a pregnancy lasts for 40 weeks, calculated from the first day a woman has her last period. The conception itself is typically 2 weeks after that first day of period, although it varies from woman to woman. So during the first two weeks, technically a woman is not pregnant yet. If a woman is 10 weeks pregnant, that means the baby is actually only 8 weeks old.

That's why if you ask expecting parents how far along the pregnancy is, they usually will answer you in weeks, not in months. Otherwise it will be too confusing because 40 weeks equals to 10 months. If someone says she is 7 months pregnant, then you would think she will be due in 2 months, which is not true because 7 months = 28 weeks, thus she still has 12 weeks to go (or 3 months to go). 

Talk about math problem!