LOL, what? Russia’s fertility rate is 1.5. I think it’s safe to say shortening gestation won’t affect that at all.
Shortening of gestation period is bad: Compared with children born at 39-40 weeks, those born at 37-38 weeks had an up to 30 percent higher risk of attention deficit hyperactivity disorder and a 10-40 percent higher risk of cognitive problems.
But if Putin is looking to feed the meat grinder...
The fertility rate in Russia is going down fast in 2022 it was 1.36 in the rural areas and 1.42 in the cities. See graph. https://www.statista.com/statistics/1005471/fertility-rate-russia-area/
It is most likely lower today.