The eighth-month fetus: classical sources for a modern superstition.

Among obstetric patients from diverse backgrounds, we found a superstition that the prognosis for preterm infants born at eight months' gestation is poorer than for those born at seven months. After several women on a high-risk inpatient unit spontaneously expressed fears caused by this belief, we investigated its origin. A treatise attributed to Hippocrates is devoted to the idea, which appears to have been current in the Greek world by the fifth century BC. The doctrine was elaborately developed by subsequent Greek physicians and philosophers. It appears in the Talmud and in medieval texts, as well as in early modern medical writings. The unquestioning citation of a dogma of the Ancients until modern times is a common phenomenon in medical history. The persistence of this ancient scientific doctrine as an "old wives' tale" causing inappropriate patient anxiety makes it interesting to the modern obstetrician.