Maternal "S. pyogenes" infection usually happens in late pregnancy; at more than 30 weeks of gestation to four weeks postpartum, which accounts for 2 to 4% of all the "S. pyogenes" infections. This represents 20 to 100 times increase in risk for "S. pyogenes" infections. Clinical manifestations are: pneumonia, septic arthritis, necrotizing fasciitis, and genital tract sepsis. According to a study done by Queen Charlotte's hospital in London during the 1930s, the vagina was not the common source of such infection. On the contrary, maternal throat infection and close contacts with carriers were the more common sites for maternal "S. pyogenes" infection.