My husband used clobetasol propionate on several areas, one of them is rather large. we are trying to conceive. could this effect his sperm or baby?

Very very unlikely: It is a potent corticosteroid which can affect your husbands skin if used in excess. If you are having difficulty in conceiving an infant then you should BOTH go for a fertility workup together where amongst other things his sperm will be examined for both number, quality, morphology and motility. It's not all you you know. It's a joint project right from the get go. Good luck!