Pregnancy folklore revisited: the case of heartburn and hair.

BACKGROUND Folklore can originate by detection of actual associations between seemingly unrelated events and perpetuated through oral tradition. The objective of this study was to determine whether a common pregnancy belief that women who experience a lot of heartburn give birth to newborns with a lot of hair is accurate. METHODS Sixty-four pregnant women ranked the severity of their degree of heartburn during pregnancy. Independent coders rated newborn hair volume using 2 photographs of the infant's head, taken shortly after birth. RESULTS Most (78%) women reported some degree of heartburn. Symptom severity was unrelated to fetal sex and maternal characteristics including parity, age, or weight. The simple linear relationship between heartburn severity and hair volume was significant r(s)(62) = 0.40, p < 0.001. Categorical analysis by severity score and hair ranking revealed a similar association (chi(2)= 23.93, p < 0.05). Most (23/28) women who reported moderate or severe heartburn gave birth to babies with average or above average amounts of hair, and conversely, most (10/12) women reporting no heartburn had babies with less than average or no hair. CONCLUSIONS Contrary to expectations, it appears that an association between heartburn severity during pregnancy and newborn hair does exist. We propose a shared biologic mechanism involving a dual role of pregnancy hormones in both the relaxation of the lower esophageal sphincter and the modulation of fetal hair growth.