As far as I know the practice started to become popular in the 1880s. It was used as an anti-mastubation measure by John Harvey Kellogg. Here is a quote from his book Plain Facts for Young and Old (1888) "The operation should be performed by a surgeon without administering an anesthetic, as the brief pain attending the operation will have a salutary effect upon the mind, especially if it be connected with the idea of punishment, as it may well be in some cases. The soreness which continues for several weeks interrupts the practice, and if it had not previously become too firmly fixed, it may be forgotten and not resumed."

He advocated parents should circumcise their boys, pour pure carbolic acid on girl's clitoris, and give their kids plain foods like his corn flakes. The "hygiene argument" was used later on (WWI), to help further the cause. There was no real evidence that it was cleaner or that it prevented STDs. This is probably why you couldn't find anything to support your midwife's claim. Even today people believe it is cleaner. And for every scientific study showing that HIV infects uncircumcised people more, there is one that shows the opposite. Evidence shows that UTIs, HIV, and most other health problems are actually lower in other countries where circumcision is uncommon (europe, asia, latin america). The only health problem that is helped by circumcision is penile cancer. However penile cancer is extremely rare in either case, and the potential complications (infection, adhesions, or even death), negate the preventative "benefits" of preventing a rare disease. If foreskin was really unhealthy, humans and every other animal would not have evolved to have it.