The hormonal changes that take place in a woman's body during the nine months of pregnancy is the reason behind the unconditional love that she later feels for her children. In fact, research has determined that the gestation period modifies the nucleus accumbens. This is a brain structure linked to the experience of pleasure, motivation and reinforcement, and causes the mother to "fall in love with her baby". This is a basic system for maternal behaviour in mammals, as it allows the female to be attracted to the stimuli coming from the baby as soon as she is born.
A recent study carried out by the Hospital Gregorio Marañón in Madrid and the Cibersam concludes that, after pregnancy, the baby becomes the most striking, relevant and pleasant stimulus for the mother, so that she initiates a series of behaviours aimed at promoting and guaranteeing the survival of the child, just as occurs in the animal kingdom.
The main researcher of this study, Susana Carmona, explains that during pregnancy the organs of the pregnant woman change to be able to adapt to the new state and up until now no data was available in understanding what goes on in the brain; "what we have been able to prove is that the more the brain changes during pregnancy, the more the mother-child bond increases", she says.
The study analyzed data obtained from new mothers, before and after pregnancy, through brain magnetic resonance imaging. It first examined whether there were volumetric changes in the nucleus accumbens and also whether those changes were associated with activation of this region when the women were shown images of their babies.
The researchers found a decrease in the volume of the nucleus accumbens in women after their first pregnancy and the more it decreased, the more this area in the mother's brain was activated when she saw stimuli related to her child. "In short, during pregnancy, regions of our brain are modified that make it easier for mothers to fall in love with their babies," Carmona added. This data indicates that maternal behaviour, in humans, is conditioned by primitive and instinctive systems that we share with other more basal mammals, such as rodents.
Determining how women's brains change during the gestation period can help us "better understand what happens at the brain level in postpartum diseases, such as depression, that put at risk not only the mother's health but also that of the newborn," says Carmona.
Research has also shown that, according to MRI tests, these changes in the brain are maintained for at least two years, something that could be related to the fact that, from that point on, the child begins to be more autonomous. However, the scientist anticipates that an attempt will be made to follow the mothers who participated in the study for six years.
Do foster parents experience this too?
The sample in this study included 25 new mothers and, as a control group and 20 nulliparous women (women who have never given birth). Regarding the activation of the nucleus accumbens in fathers and nulliparous mothers, Carmona points out "that there are no studies available". However, research conducted with animals seems to indicate that this region is activated "by interaction with the offspring, even if it requires more time".