Of course birth rates fall during wartime. And they usually also explode afterwards, at least in the short term - hence the baby boom in the U.S. and Europe post-WW2. Having kids puts you in a precarious position -logistically, financially, emotionally. It's natural for people to defer this during an existential war of survival.

And even the pre-war state of ukraine, with it's terrible neighbor's corrosive meddling and the apparently well-foudned fear of an eventual invasion hanging over people's heads would create uncertainty that would make you think twice about having kids.

The template for a post-war Ukraine is the same as Poland, Romania & Czechoslovakia's. Namely - integration to the EU and NATO produce sovriegn stability and economic growth. But - as history also shows - economic growth leads to falling long term birth rates, everywhere it's happened. Lots of factors there - economic activity makes people chase opportunity, women have more control of working and reproductive rights, you don't need to have 12 children, expecting half of them to survive, to pick potatoes on the farm.

Point being - this war is like a national divorce. One that has been 1,000 abusive years in coming. Ukraine is not going to be the same as it was before. And neither is Russia. But that's okay. If Ukraine can survive the war, integrate with the EU and NATO, and Russia fucks off into it's murky, corrupt, increasingly irrelenvant future too focused on it's own internal squabbles to spend resources murdering it's neighbours - then Ukraine's new form will, like all the former Eastern bloc colonies, be prosperous and free.