Having children is contagious among female high school friends during early adulthood. This is the conclusion of a study conducted by Nicoletta Balbo, a postdoctoral fellow at the Carlo F. Dondena Centre for Research on Social Dynamics at Bocconi University in Italy, and Nicola Barban, a postdoctoral fellow in the department of sociology at the University of Groningen in the Netherlands.
The data for the study was extracted from the National Longitudinal Study of Adolescent Health in the United States. The researches tracked the childbearing behaviors of 1,700 women from the age of 15 until the women were 30 years of age. The average age at first birth for women in the study was just over 27-years-old. There was an extremely high level of synchronicity in childbearing and apparently fertility among women that knew each other in high school. This is the first research that proves women have babies in a manner that could be considered contagious.
The researchers conclude that the observed behavior has a basis in personality and practicality. Having a child is a status symbol and many women want to be competitive with their peers. Having children at the same time offers mothers the advantage of the experience of other women that face the same problems with childbearing and rearing and offers a social circle that is supportive. Synchronicity in menstrual cycles might be an element in the phenomena for women that remain in physical proximity to each other but the study indicates that contagious babies do not require physical proximity.
One element that might cause the contagion of childbearing is evolutionary. The researchers do not examine this possibility. In the most ancient of human societies, having children was often coupled with the seasons of the year. It was easier to raise a child and keep them alive in the spring and summer. Physical proximity of women to other women of childbearing age may have contributed to synchronous menstrual cycles. There may be an unknown genetic evolutionary component in women that promotes contagious birthing.