Maternal hair cortisol levels affect neonatal development among women conceiving with assisted reproductive technology.

: To compare stress levels throughout pregnancy in women who had conceived using assisted reproductive technology (ART) and women who had conceived naturally and somatometric values for infants. : Pregnant women who have received ART are exposed to high levels of stress. : Ninety-one women attending a prenatal appointment at a Health Centre (Granada, Spain), and their 91 newborns participated in this study: 69 women conceiving naturally and 22 conceiving using ART. Assessment consisted of measuring hair cortisol levels, the Prenatal Distress Questionnaire, the Perceived Stress Scale and the Symptom Checklist-90-Revised. : Women conceiving using ART had higher cortisol levels in the first trimester than women who conceived naturally. In the third trimester, women who used ART reported higher levels of perceived stress than those who had conceived naturally. Maternal cortisol levels in the first trimester explained 32% of the variance in neonatal head circumference in the group of women who had conceived using ART. : Women who had conceived using ART showed higher levels of cortisol in the first trimester and higher levels of perceived stress in the third trimester than women who had conceived naturally, rendering them more vulnerable to adverse outcomes. Maternal cortisol predicted the infants' development.