3 Look! Sons are an inheritance from Jehovah;
The fruitage of the belly is a reward.
4 Like arrows in the hand of a mighty man,
So are the sons of youth.
5 Happy is the able-bodied man that has filled his quiver with them.
They will not be ashamed,
For they will speak with enemies in the gate.
Rebel 8,
The plain interpretation is that having many offspring, esp sons, was considered as a blessing by YHWH; children being the "fruitage of the belly" (beten, lit. a bag, often interpreted as being the reproductive systems of men and women).
If a son was born, they broke out the fine reserve wine and cigars; if a daughter, soft drinks only). Having many sons was being very blessed. Many sons as arrows meant more arrows to carry in the quiver (case). Obviously good to have strong able-bodied sons to defend you from enemies.
It's hard to imagine that there'd be some ominous interpretation to suggest it's encouraging child abuse, as the scripture refers to the value of children (esp sons). It also works as a loose connection to their anti-abortion stance, I suppose.