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(view spoiler)[haven't finished the book yet but just got to the discussion with vronsky + anna where she says the baby is due soon and how has no one noticed she's pregnant? I mean she must have some sort of visible baby bump? Did i just skim over some section? Also, when does she tell her husband she's pregnant because he must've noticed as well? (hide spoiler)]
Agnieszka Hello! I'm not a specialist in this matter but I think period dresses of the time, especially ones worn by ladies of high society had very wide, voluminous skirts... so made baby bump not visible for a long time. Also I may be wrong but at this point Anna was no longer sleeping with her husband, so he also has not seen her undressed. It would be actually possible to hide the pregnancy for a long time. Another thing is, remember we are not talking of modern society a lot more taboos there. It is possible that Anna just did not tell her husband, especially that the child was not his.