both mother and child
Fixed expression used as a noun or adverbial phrase to indicate that something applies to both the mother and the child together, often in medical or welfare contexts.
母子ともに健康です。
Both mother and child are healthy.
母子とも無事で何よりだ。
I'm relieved that both mother and child are safe.
Variant using 共 instead of とも; less common but still seen.
Compound of 母子 (mother and child) + とも (both, all).