[1] Yale Univ, Sch Publ Hlth, Dept Chron Dis Epidemiol, New Haven, CT USA
[2] Brown Univ, Sch Publ Hlth, Int Hlth Inst, Providence, RI 02912 USA
[3] Chaminade Univ, Dept Nat Sci & Math, Honolulu, HI USA
[4] Lyndon B Johnson Trop Med Ctr, Dept Obstet & Gynecol, Pago Pago, AS USA