The Largest Vagina
The Largest Vagina most likely belonged to Scottish giantess Anna Swan (1846-1888), a remarkable woman who set a number of records relating to her bulk. Born normally sized, she began growing at a prodigious rate in childhood, finally reaching a maximum height of 7' 8" at age 19. Capitalizing on her huge size, she joined a side show and toured the country, where she met and fell in love with Captain Martin Bates, another giant who measured over 7 feet tall. They wed in 1872, making them the tallest married couple in the world, a record that still stands today. The couple settled down into married life, built a mansion filled with enormous furniture, including an 11' by 7' bed where they consummated their union. On June 18, 1879, she gave birth to the largest baby in history, weighing 26 lbs. and 34 inches in length—so large, in fact, that it became tightly wedged in her capacious tract, only extricated by the use of forceps and belts. The child did not survive the rigors of birth, but a cast was made, still on display at the Cleveland Museum of Health.
Generally the largest part of an infant is the head. We know that the tyke's cranium measured about 19 inches in circumference, hence we compute the minimum dilation of Swan's passage as 6 inches, or just over 15 cm. That's pretty wide—the normal dilation for childbirth is 10 cm.