A new study may have found out why religious couples tend to have more kids than their secular counterparts.

The University of Otago research used 10 years of data from up to 1700 UK families.

Lead author John Shaver told Mike Yardley it seems to come down to social support.

"The strong support networks of religion help women, at least in the UK, have more successful children."

"We found couples who have a lot of support from their congregations tend to have more children - and they often perform better in school than kids from other large families."

Shaver says in general, having more siblings is associated with poorer outcomes for kids, but this doesn't seem to be the case for religious communities.

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