Are Increses in Preterm Birth and low birth rates related to the rise in multiples, instead of pover

The rise in preterm delivery (That is, before 37 weeks gestation) has increased 30% since 1980. (www.marchofdimes.com...)

About 8% of babies are born with a low rate (Less than 5 pounds, 8 ounces.)

Usually people point the finger at socialeconomic factors, but I suspect the increase is actually due to a rise in multiple births.

According to this article, multible births rose 59% since 1980!