All the versions other than King James reads increase your pain of childbirth. Doesn’t have anything to so with the frequency of conception or whether the sex was primarily recreational vs reproductive.
http://biblehub.com/text/genesis/3-16.htm
This link takes you to the Hebrew for Genesis 3:16 which supports my point.
If God didn’t intend sex to recreational, He wouldn’t have given man such a strong desire for it or made it so enjoyable. he could also have created woman to go into heat if it were just for procreation.