Asthma is a common disease and many women conceive and give birth without any problem despite their treatment. Ventolin, in particular, is used extensively in pregnancy and is as safe as any drug. Serevent and Becotide are listed as requiring special care in pregnancy, but no specific risks are listed.
Inhaled drugs for asthma do not have any effect on male fertility. It is true that the preventative inhaler is a sort of steroid, but it is a very low dose and its effect is confined to the lungs. Ventolin can increase the pulse rate as well as open the air passages, but it does not affect the sperm count. Generally speaking, even when the drugs taken for a particular illness might have an effect on male fertility, it is almost always a lesser effect than the illness itself has, so the therapy shouldn’t be stopped.