9 months is long and short. Is the time between conception and birth set in stone? In the Napoleonic Code of 1804, a child was potentially viable at 6 months. Since then, things have more or less changed. In France, the gestation period is 9 months. In the rest of the world, it is defined as 40 weeks of amenorrhea. Medical advances in neonatology in the 1980s succeeded in reducing viability times to less than 6 months, though without a formal status. In 1993, the World Health Organization set the threshold for viability at 22 weeks of amenorrhea and a weight of 500 grams (just over a pound). Is this a utopia or a reality? Is gestation set in stone? Or does it vary from one woman, one pregnancy, and one fetus to another? Can we – or should we – attempt to shorten gestation? And for whose benefit? These are pressing health questions for future generations.