Her family says the due date was February 14th...which would make her conception date May 24th - weeks after she and Laurean are ordered to stay away from each other. The Marine Corps medical says the date of conception was May 14th, which would make her due date February 4th.
Maybe out of novelty's sake since February 14th is Valentine's Day, she told people the baby would be a Valentine's Day baby.
OBGYNs usually go by weeks for measuring pregnancy, not months and the ninth month is the longest month of pregnancy. The eighth month is from 32-35 weeks according to 'What To Expect When You're Expecting' and the ninth month is considered to be between weeks 36-40+ weeks (first time births can take weeks longer). On December 14th, Maria was only a few days away from her 33rd week.
You're right, she was eight months pregnant, but her conception date would have been in mid-May.