Authors: Stephen T Chasen; Robin B Kalish; Meruka Gupta; Jane E Kaufman; William K Rashbaum; Frank A Chervenak Journal: Am J Obstet Gynecol Date: 2004-05 Impact factor: 8.661
Authors: M Melbye; J Wohlfahrt; J H Olsen; M Frisch; T Westergaard; K Helweg-Larsen; P K Andersen Journal: N Engl J Med Date: 1997-01-09 Impact factor: 91.245