Historical notes on immaturity. Part 1: measures of viability.

The interest in the limit of viability originated from various sources, including legal requirements, the rejection of mechnical life support, competition for resources, concerns about handicaps, and proximity to the fetus with its limited rights. Gestational age was determined from menstrual history by Hippocratic writers, who established the tenacious idea that 7-, but not 8-month infants could survive. Naegele's rule, already published by Boerhaave in 1744, was correct when applied to the last day of menstruation. Birth weight and length were not measured until the end of the 18(th) century. This remarkable disinterest resulted from superstition, grossly inaccurate measurements by the authorities Mauriceau and Smellie, and the conversion chaos of the pre-metric era. A table is provided with historic mass and length units allowing to determine birth weight and body length in the older literature. The idea of viability is a remnant of vitalism, a medical doctrine popularized in 1780 by Brown. Many short-lived statements defined its limit, but until now what was meant by viability remained nebulous.