The term expecting is often used as if it means "pregnant", as shown by Merriam-Webster (for the verb expect)
3 : to be pregnant : await the birth of one's child —used in progressive tenses
she's expecting next month
and Oxford Dictionaries says
informal Be pregnant.
‘his wife was expecting again’
but logically you can only be expecting if you are knowingly pregnant and anticipating a successful conclusion.
There seem to be two issues here. One is how we should use terms that are metaphorical in origins in particular contexts where the original meaning seems to be the opposite of the derived meaning.
The other is whether we should go by the dictionary when we suspect the dictionary writers were not specific enough in their definition.
Note that this question was motivated by a news report that said that surgeons "discovered that [Ebony, who did not previously know she was pregnant] was expecting a baby [while she was in a coma], and I thought, "How could she be expecting a baby or anything else whilst in a coma?"
Best Answer
It’s a euphemism. From the etymonline entry for "pregnant":
The use of it always reminds me of a Lady Whiteadder (Blackadder's aunt) quote source
It is a means of saying a baby is present but concealing the act of conception (because sex is "hardly a fitting subject" in polite company). Personally, I know where babies come from, so I’d take no issue with just saying "pregnant", but the contents of the news story you reference is already quite scandalous, so maybe the writer is simply attempting to tone it down for the more conservative amongst us.