[1] Univ Med Ctr Groningen, Groningen, Netherlands
[2] Stellenbosch Univ, Cape Town, South Africa
[3] Univ Leicester, Leicester, Leics, England
[4] Texas Childrens Hosp, Baylor Coll Med, Dept Obstet & Gynecol, Houston, TX 77030 USA
[5] Uppsala Univ, Uppsala, Sweden