[1] Penn State Univ, Milton S Hershey Med Ctr, Dept Obstet & Gynecol, Hershey, PA 17033 USA
[2] Duke Univ, Med Ctr, Dept Obstet & Gynecol, Durham, NC 27710 USA
[3] Duke Univ, Med Ctr, Duke Clin Res Inst, Durham, NC 27710 USA
[4] Baylor Coll Med, Dept Obstet & Gynecol, Houston, TX 77030 USA
[5] Wayne State Univ, Detroit, MI USA
[6] Univ Texas, SW Med Ctr, Dallas, TX 75230 USA
[7] Univ Colorado, Denver, CO 80202 USA
[8] Univ Penn, Sch Med, Philadelphia, PA 19104 USA
[9] Univ Med & Dent New Jersey, Newark, NJ 07103 USA
[10] Stanford Univ, Palo Alto, CA 94304 USA
[11] Univ Alabama Birmingham, Birmingham, AL 35487 USA
[12] Virginia Commonwealth Univ, Sch Med, Dept Med, Richmond, VA USA
[13] Univ Pittsburgh, Pittsburgh, PA 15260 USA
[14] NICHHD, Reprod Sci Branch, Bethesda, MD 20892 USA