Author(s) affiliations:Jaana Nevalainen1, Mikko Sairanen2, Heidi Appelblom2, Mika Gissler3, Susanna Timonen4, and Markku Ryynänen1
1Department of Obstetrics and Gynecology, PL 24, 90100, Oulu University Hospital, FINLAND.
2Perkin Elmer, PL 10, 20101, Turku, FINLAND.
3National Institute for Health and Welfare, P.O. Box 30, FI-00271, Helsinki, FINLAND.
4Department of Obstetrics and Gynecology, PL 52, 20521, Turku University Hospital, FINLAND.