I wasn't assuming pre-war birth rates. [1] suggests 45~50k/yr; [2] suggests ~34k/yr. They're rough figures, ignoring seasonality etc, but it's clear that there are significantly more births than GHM-reported casualties.
There's certainly food insecurity but it would need to get way worse to make a dent in these numbers; so far it's about 100 reported deaths linked to malnutrition during the conflict.
There are really only those two options.