Dr. Crusher explains to the Aldeans that their shield has weakened the ozone layer of the planet, exposing the inhabitants to ultraviolet radiation, leaving them unable to bear children and would likely have the same effects on the children from the "Enterprise".
Their shield has weakened the ozone layer of the planet. This is what Dr. Crusher explains to the Aldeans. Their shield was exposing the inhabitants to ultraviolet radiation. This is what Dr. Crusher explains to the Aldeans. Dr. Crusher was leaving them unable to bear children. Dr. Crusher would likely have the same effects on the children from the "Enterprise".