Answer:
Most likely because of potato famine. A lot of starvation happened and there were diseases.
The period saw major technological advances, including the adoption of gunpowder, the invention of vertical windmills, spectacles, mechanical clocks, and greatly improved water mills, building techniques (Gothic architecture, medieval castles), and agriculture in general (three-field crop rotation)
Children killed when they arrived in killing centers
children killed immediately after birth or in institutions
children born in ghettos and camps who survived because prisoners hid them
children, usually over age 12, who were used as forced laborers and as subjects of medical experiments