I know a couple who is heartbroken because they cant conceive. Sometimes concessions should be made.
There
are licit means for helping subfertile couples. The Pope Paul VI Institute in Omaha is one example. It's website is
here.
My wife and I tried to conceive for 3 years before Dr. Mark Stegman (now in the Harrisburg, PA area), who was trained at the Pope Paul VI Institute, operated on my wife's endometriosis. Dr. Stegman prescribed femara for ovulation and progesterone for pregnancy support. Our son was born in January!
People who suffer from subfertility (as I know I did) should know, too, that sometimes it's related to nutrition. Marilyn Shannon, author of "Fertility, Cycles,and Nutrition," has helped probably thousands of couples to get pregnant. You can get that book for under $5 at:
http://www.amazon.com/gp/product/0926412094/002-5423294-3388818?v=glance&n=283155
A good summary of approved Reproductive Technology for Catholics can be found here:
http://www.usccb.org/prolife/issues/nfp/treatment.htm