A reader points out what is left implicit in the Palins' statement:

I'm not sure how to say this politely, but if Bristol Palin is more than three and a half months' pregnant, it is physically impossible for her to have given birth on the 18th of April to Trig.

I know with "about five months" it's difficult to be certain what they mean, which is why most doctors talk in weeks. But basically a pregnancy is calculated as 40 weeks, and is dated from the previous period so for the first two weeks of the 'pregnancy' one is not actually pregnant.



Women tend to take at least six weeks to start ovulating again, and often several months. Say Bristol is very young and made a medically exceptional recovery - the very very earliest she could have become pregnant 'again' would be from mid May, which would put her at three and a half months pregnant.

Also, and for me this is the clincher: