In the United States, a typical mature male weighs 50 lb (23 kg), while mature females weigh about 40 lb (18 kg). The Bulldog Club of America recommends the average weight of a bulldog to be 40–50 lb (18–23 kg).Bulldogs are one of the few breeds whose tail is naturally short and either straight, screwed or thin and thus is not cut or docked as with some other breeds. Over 80% of Bulldog litters are delivered by Caesarean section because their characteristically large heads can become lodged in the mother's birth canal. The folds, or 'rope', on a Bulldog's face should be cleaned daily to avoid infections caused by moisture accumulation. Some Bulldogs' naturally curling tails can be so tight to the body as to require regular cleaning and ointment.