Before revision: The German obstetrician Mr Welheim Horkel, when visiting a medical mission in the mid-1980s, learned that African tribes used gourds of increasing sizes to stretch the perineum .
After revision: to avoid damage of childbirthThe German obstetrician Mr Welheim Horkel, when visiting a medical mission in the mid-1980s, learned that African tribes used gourds of increasing sizes to stretch the perineum .