It's the season for Virgin Birth discussion

The Times has a lightweight piece about the importance of baths, which mentions a legal case that I had never heard about before:

For much of the 20th century it was popularly believed that a woman should never get into the bath after a male member (no pun intended) of the household. The fear was that if he had been abluting himself a little too vigorously she might be in danger of impregnation. The famous paternity case involving Lord Ampthill gave this myth widespread credence. He filed for divorce after his wife produced a son, even though the marriage had not been consummated. It was suggested that she had conceived after using a sponge in a bath they had shared.

A Google search turns up this Time Magazine article from 1976 ("Was Mother a Virgin?") about the case (which happened in the 1920's). The sponge theory doesn't get mentioned, but I assume it must have come up in court as one of the theoretical ways that a "virgin birth" can happen.