Being a Midwife I jumped to the conclusion Linda was pregnant when she appeared to seemingly put on weight & get puffy in the face, especially when the story-line seemd to be going in that direction (when she split up with the greasy side-kick).
However after looking her up & noting when the series had been recorded, it seems Johanna was suffering from depression, after being in the 2004 Tsunami. Anti-depressants can cause those sort of side-effects.
Unfortunately she commited suicide in 2007 & Mankell did not finish the books he was writing based on the Linda Wallander character as he was so devastated - allegedly.
We watched the 2nd series before this one & I have to admit, I did prefer it.