I've been wondering lately, why everyone is so prone to thinking a woman is pregnant when she has persistent nausea, even if their period ended just two days prior to the last ual they had. I mean, sure there are ways for that to happen; but mostly it's known that you don't get pregnant unless it's the day of your ovulation +/- 3 days. Even if you have every two days - which is the frequency that has the highest pregnancy rate - and you have a fertile male and fully healthy female at their best, the chance of pregnancy per cycle is around 20%.

So saying that, even if our main lead Yeojin didn't have her period that soon, her chances of getting pregnant from that single night would be about 20%. And the only symptoms being nausea and vomiting, it's hard to judge that as pregnancy for those symptoms have a very wide range of diagnosis available. Stress gastritis is one of the most common and there are a lot of cases that are resistant to medical treatment and need stronger meds. It also could be an infection in your stomach, psychological problem, neurological problem, other stomach problems... yet here we are, thinking "she's so obviously pregnant!!" 

I don't mean anything bad here, it is indeed obvious that she would be pregnant by the way the story is going. That needs to happen for the whole plot to evolve - sorry for the spoilers given here, though I'd assume all of you already guessed that much. We all know here that "did they have ? okay then she's absolutely gonna get pregnant" rule works with a close to 99% accuracy as long as there's drama involved... I'm just wondering why, even if all the odds are against it, we tend to think about that first.

Anyone with an idea here? :3