Actually, unless I'm mistaken, I think the time gap between the Christmas special and the season finale is only sixm months.
According to these websites Edith already gave birth in Switzerland and had the child adopted. If this turns out to be true, I have only one thing to say: ARGH!!!
There is always the possibility that those articles were wrong, I admit. Rose's parentage was reported wrongly before the true account was reevaled. I certainly pray with all my heart that they are wrong.
Unfortunately now it seems likely that she did go to the continent and return without a child. I said I would say it, and I will, AAAARGH!!!!!!!!!!!!
I checked; a woman's pregnancy cycle lasts roughly nine months. The "bump" begins to appear after six. Whatever date it was that Edith got pregnant from sleeping with Michael, that should give an estimate as to when she gives birth. But given that she and Michael slept together in the middle of the series, my hope is really dim now. :(
Utterly confused at when the Christmas special is set. The same source claims it takes place in the summer and also 6 months after the church bazaar. Unless the episode itself spans at least 4 months then something does not add up. (http://www.radiotimes.com/news/2013-12-21/downton-abbey-christmas-special-8-things-you-need-to-know) So who knows what stage of pregnancy or post-partum Edith will be in...
As a pregnant woman, the "bump" can appear at various stages, depending on the woman. I didn't show at all with my first until 7-8 months, but my second I was showing fully by 3 months.
What do you think?