Determining paternity before DNA - the significance of pregnancy duration

Questions concerning paternity have been of major interest over the centuries. Issues such as legitimacy, fidelity, inheritance and child maintenance have been central. Maternity was unequivocal, but paternity could be uncertain. A key issue in paternity cases was whether the mother's account of sexual intercourse was consistent with the timing of the birth. This required an understanding of the possible duration of pregnancy. We examined how law and forensic medicine assessed the significance of pregnancy duration in establishing paternity throughout the 20th century.

The study is based on a review of paternity case judgments by the Norwegian Supreme Court in the 20th century with regard to pregnancy duration in the context of historical obstetric literature.

Well into the 20th century, knowledge of pregnancy duration was primarily of interest in forensic medicine. Paternity could be ruled out but not established. In 1914, the Norwegian Forensic Medicine Commission defined pregnancy duration as 240-320 days, and this became the standard in Norwegian law for much of the 20th century. The courts made an overall assessment in which pregnancy duration and the mother's credibility, conduct and sexual morality were taken into account. Around 1990, DNA typing replaced blood group testing and discretionary assessments, and paternity disputes largely disappeared from the courts.