Scientists, including one of Indian-origin, have for the first time used infant hair to examine the hormonal environment to which the foetus was exposed during development.
Researchers at the University of Wisconsin-Madison studied rhesus monkeys and found that hair can reveal the womb environment in which an infant formed.
"We had this 'Aha!' realisation that we could use hair in newborns, because it starts growing one to two months before birth," said Christopher Coe, UW-Madison professor of psychology and director of the Harlow Center for Biological Psychology.
"It provides a glimpse of the prenatal hormone environment," Coe said.
Hair closest to the scalp gives the most recent information but moving down the shaft effectively transits an individual's hormonal timeline.
For the noninvasive study, researchers took small samples of hair from mother rhesus monkeys and their infants using common hair clippers.
The hair was cleaned and pulverised into a fine powder using a high-speed grinder. The hormonal signature was then read using a new mass spectrometry method.
The researchers were interested in whether there were differences in the hormones of infants born to younger, first-time mothers versus more experienced mothers.
To test their question, they compared monkey mothers equivalent in age to 15-year-old humans to older monkeys, similar in age to pregnant young adults.
The researchers used rhesus monkeys because they are an ideal model species for humans.
In the monkey study, researchers found that cortisone, an inactive form of cortisol, was higher in young mothers and in their babies than in hair of the older mothers and their infants.
Babies born to young mothers also had higher levels of estrone (a form of estrogen) and testosterone in their hair than did babies born to older mothers. Levels of both these hormones were surprisingly similar between male and female infants.
Both Coe and Amita Kapoor, first author of the study and former postdoctoral researcher in Coe's lab, are particularly interested in whether these differences impact "maleness and femaleness" of the babies: whether higher exposure to these steroid hormones during foetal development leads to more pronounced gender differences in behaviour later in life.
Additionally, what happens to a developing foetus while in the womb may impact its risk for chronic disease later in life, said Kapoor.
"Type 2 diabetes, metabolic disease, coronary artery disease, psychiatric disorders - there [may be] a whole host of long-term repercussions of stress in utero," said Kapoor.
The study was published in the journal Pediatric Research.
