[1] John H Stroger Jr Hosp Cook Cty, Dept Obstet & Gynecol, Chicago, IL 60612 USA
[2] Childrens Mem Hosp, Chicago, IL 60614 USA
[3] Univ Illinois, Coll Med, Dept Cardiol, Chicago, IL USA
[4] Univ Illinois, Coll Med, Dept Obstet & Gynecol, Chicago, IL 60612 USA
[5] Univ Illinois, Sch Publ Hlth, Div Community Hlth Sci, Chicago, IL USA