I see two possibilities here. One is that Ukraine's manpower is so low that they have to increasingly rely on women. The other is that this is some kind of globohomo op along with all the fictional pregnant women that appeared in games and movies in the last 5 years.

One is almost certainly true, two is a little more out there but the fact that they not only allow pregnant women to serve, but are also highlighting them, makes me lean in that direction.