[1] Univ N Carolina, Sch Nursing, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Div Maternal Fetal Med, Dept Obstet & Gynaecol, Chapel Hill, NC 27599 USA
[3] Albert Einstein Coll Med, Dept Family & Social Med, Rochester, NY 14602 USA
[4] Dept Obstet Gynecol & Womens Hlth, Bronx, NY 10461 USA
[5] Rex Healthcare Inc, OB GYN, Raleigh, NC 27607 USA
[6] WakeMed Hlth & Hosp, WakeMed Fac Phys, OB GYN, Raleigh, NC 27610 USA
[7] Univ N Carolina, Gillings Sch Global Publ Hlth, Dept Maternal & Child Hlth, Chapel Hill, NC 27599 USA