1. Department of Perinatology, Zekai Tahir Burak Women's Health Education and Research Hospital, Ankara, Turkey,
2. Department of Obstetrics and Gynecology, Gazi University Medical School, Ankara, Turkey,
3. Department of Biochemistry, Gazi University Medical School, Ankara, Turkey, and
4. Department of Biostatistics, Hacettepe University Medical School, Ankara, Turkey