I'm sure that she got pregnant after 48 days, which means the earliest she could say she got pregnant by Jin was the night before the flight, 49 days. That's 7 weeks, which is a lot in a pregnancy of average 40 weeks.
She also seemed quite relieved when she thought about proper medical care ina proper hospital when she knew she would be going home(I think she said it to Claire??) I'd think that the first thing she would do was to see a proper doctor, who would dosome sort of scan for dates and checks etc...
