Pregnant? Get Ready To Unfold These Mysteries

With all the information now available to us about pregnancy, labor, and delivery, it can be easy to feel that we know all there is to know. But the truth is, there is still a lot of mystery surrounding pregnancy and birth.

1. Your uterus is one tough cookie. The force inside a woman's uterus from pushing with a contraction translates to 397 pounds of pressure per square foot, or 2.8 pounds of pressure per square inch on her baby's head.

2. You can get pregnant when you're already pregnant. Pregnancy sex is supposed to be care- (and contraceptive-) free, but on rare occasions, women have gotten pregnant twice. It happened to a woman in Arkansas, who carried two children with two different due dates.

3. One size does not fit all. There are actually four different shapes that a woman's pelvis can take. Unfortunately, only one is best for accommodating a baby's head during childbirth -- the gynecoid. Fortunately, that shape happens to be the most common.

4. That waddle is not your fault. Feeling self-conscious about your duck walk? It may not have anything to do with your size or weight. "The waddle is actually due to the fact that the joints become more relaxed and the center of gravity changes.

5. What was that noise? It's painful yet true, the first time a woman delivers a child, her pelvic bone will actually separate in the middle. "The cartilage stretches at the middle of the pubic bone.