Fertility: does drinking alcohol in moderation affect male fertility?

Probably, yes: The real issue is in defining "alcohol use in moderation". For many this means daily alcohol intake of 1-4 alcoholic beverages, which is significant. Alcohol use can effect male hormone metabolism which in turn can effect hormone production. Some data suggest a lower take-home baby rate with ingestion of >4 drinks per week.

Unlikely: While moderate alcohol use may not directly affect male fertility, if there are other factor that may affect one's liver and hormonal metabolism, then it may be possible. A relatively simple first step is to obtain a semen analysis, which would identify male factor infertility. If abnormal, a full evaluation by urologist is recommended.