What parts of Bella's pregnancy in Breaking Dawn could really happen? For instance, can babies crack ribs, or cause contustions and stretch the...

The most realistic aspect of Bella's pregnancy would have
to be the cravings and nausea she experiences. At one point during the honeymoon, she
wakes in the middle of the night and makes homemade fried chicken. Shortly thereafter
she experiences nausea, consistent with morning sickness. Cravings continue throughout
and while much of her pregnancy is certainly fictionalized due to circumstances, it
could be said that it is as realistic as possible considering she is carrying a vampire
baby.

For instance, the child would be strong, which could
account for the breaking of bones. Additionally, the amount of strain her body would
suffer due to a gestation that occurred twice as quickly would certainly weaken a human
body, as we are not built to adjust as quickly as her pregnancy
developed.

There are some cases in existence where pregnant
women have endured broken ribs, but usually this is due to mitigating circumstances,
such as a cold or weak bones. As far as I know, there are no studies, nor are there
enough cases to have cause of any, on this particular topic.