I could be wrong, but I am under the impression that the Catholic Church is firmly against the use of fertility drugs.
From a USCCB document, Begotten Not Made: A Catholic View of Reproductive Technology , comes these reasonable statements:
Donum Vitae teaches that if a given medical intervention helps or assists the marriage act to achieve pregnancy, it may be considered moral; if the intervention replaces the marriage act in order to engender life, it is not moral.
Any number of morally acceptable interventions may be used to overcome infertility. For example, surgery can overcome tubal blockages in the male or female reproductive system which prevent fertilization from taking place. Fertility drugs may also be used, with the caution that large multiple pregnancies may put mother and infants at risk. There are also many ways of tracking natural reproductive rhythms to enhance the chances for achieving pregnancy. The Pope Paul VI Institute at Creighton University in Omaha, Nebraska has been successful in helping couples overcome infertility using natural methods.
"Firmly" would be an exaggeration. As Polycarp pointed out, the USCCB has come out in favor of fertility drugs, but then no one pays any attention to what they say anyway.
There is clearly a moral problem with fertility drugs, and the excerpt from the USCCB document posted by Polycarp mentions it obliquely, which is that "selective reduction" (i.e. abortion) is an integral part of the technology. The drugs inevitably cause multiple pregnancies, and the procedure assumes that you will "reduce" the number of fetuses. A Catholic could claim that they will refuse to cooperate with the "reduction" process, but they might be forced to deceive the doctors, if no graver sins are involved.
That said, medications to improve the chances of conception are not inherently immoral, even if the current state of the technology requires participation in a process in which abortion is considered an integral part.
Read my post 106. I think people are getting confused and there is no reason to be.