[1] Univ Dublin, Acad Dept Obstet & Gynaecol, Coombe Womens Hosp, Trinity Coll, Dublin 8, Ireland
[2] Univ Dundee, Ninewells Hosp & Med Sch, Dept Obstet & Gynaecol, Dundee DD1 9SY, Scotland
[3] Univ Dundee, Ninewells Hosp & Med Sch, Div Maternal & Child Hlth Sci, Dundee DD1 9SY, Scotland