[1] Univ Ghent, Fac Med & Hlth Sci, Ghent, Belgium
[2] Univ Ghent, Fac Med & Hlth Sci, Geneva, Switzerland
[3] World Hlth Org, Dept Reprod Hlth & Res, Geneva, Switzerland
[4] Univ Michigan, Sch Nursing, Dept Hlth Behav & Biol Sci, Ann Arbor, MI 48109 USA