This is a common wives' tale about pregnancy and I heard it many times during the course of the various pregnancies I've recently been near. In particular, one of the infants was born with a full head of hair and I was surprised how frequently people were attributing the constant heartburn during the associated pregnancy to the child's hair.
Has such a connection ever been confirmed?
Yes, there is a connection.
Heartburn is a normal consequence of pregnancy. The predominant aetiology is a decrease in lower oesophageal sphincter pressure caused by female sex hormones, especially progesterone [1].
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. ... The simple linear relationship between heartburn severity and hair volume was significant r(s)(62) = 0.40, p < 0.001 [2].
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 [2].
References:
Richter JE. Review article: the management of heartburn in pregnancy. Aliment. Pharmacol. Ther. 2005 Nov 1;22(9):749-57. doi: 10.1111/j.1365-2036.2005.02654.x. PubMed PMID: 16225482.
Costigan KA, Sipsma HL, DiPietro JA. Pregnancy folklore revisited: the case of heartburn and hair. Birth. 2006 Dec;33(4):311-4. doi: 10.1111/j.1523-536X.2006.00128.x. PubMed PMID: 17150070.
