Becoming a mother entails anatomical changes in the ventral striatum of the human brain that facilitate its responsiveness to offspring cues.

In mothers, offspring cues are associated with a powerful reinforcing value that motivates maternal care. Animal studies show that this is mediated by dopamine release into the nucleus accumbens, a core component of the brain's reward system located in the ventral striatum (VStr). The VStr is also known to respond to infant signals in human mothers. However, it is unknown whether pregnancy modifies the anatomy or functionality of this structure, and whether such modifications underlie its strong reactivity to offspring cues. Therefore, we analyzed structural and functional neuroimaging data from a unique pre-conception prospective cohort study involving first-time mothers investigated before and after their pregnancy as well as nulliparous control women scanned at similar time intervals. First, we delineated the anatomy of the VStr in each subject's neuroanatomical space and examined whether there are volumetric changes in this structure across sessions. Then, we tested if these changes could predict the mothers' brain responses to visual stimuli of their infants. We found decreases in the right VStr and a trend for left VStr reductions in the women who were pregnant between sessions compared to the women who were not. Furthermore, VStr volume reductions across pregnancy were associated with infant-related VStr responses in the postpartum period, with stronger volume decreases predicting stronger functional activation to offspring cues. These findings provide the first indications that the transition to motherhood renders anatomical adaptations in the VStr that promote the strong responsiveness of a mother's reward circuit to cues of her infant.

Pregnancy and adolescence entail similar neuroanatomical adaptations: A comparative analysis of cerebral morphometric changes.

Mapping the impact of pregnancy on the human brain is essential for understanding the neurobiology of maternal caregiving. Recently, we found that pregnancy leads to a long-lasting reduction in cerebral gray matter volume. However, the morphometric features behind the volumetric reductions remain unexplored. Furthermore, the similarity between these reductions and those occurring during adolescence, another hormonally similar transitional period of life, still needs to be investigated. Here, we used surface-based methods to analyze the longitudinal magnetic resonance imaging data of a group of 25 first-time mothers (before and after pregnancy) and compare them to those of a group of 25 female adolescents (during 2 years of pubertal development). For both first-time mothers and adolescent girls, a monthly rate of volumetric reductions of 0.09 mm3 was observed. In both cases, these reductions were accompanied by decreases in cortical thickness, surface area, local gyrification index, sulcal depth, and sulcal length, as well as increases in sulcal width. In fact, the changes associated with pregnancy did not differ from those that characterize the transition during adolescence in any of these measures. Our findings are consistent with the notion that the brain morphometric changes associated with pregnancy and adolescence reflect similar hormonally primed biological processes.

Pregnancy leads to long-lasting changes in human brain structure.

Pregnancy involves radical hormone surges and biological adaptations. However, the effects of pregnancy on the human brain are virtually unknown. Here we show, using a prospective ('pre'-'post' pregnancy) study involving first-time mothers and fathers and nulliparous control groups, that pregnancy renders substantial changes in brain structure, primarily reductions in gray matter (GM) volume in regions subserving social cognition. The changes were selective for the mothers and highly consistent, correctly classifying all women as having undergone pregnancy or not in-between sessions. Interestingly, the volume reductions showed a substantial overlap with brain regions responding to the women's babies postpartum. Furthermore, the GM volume changes of pregnancy predicted measures of postpartum maternal attachment, suggestive of an adaptive process serving the transition into motherhood. Another follow-up session showed that the GM reductions endured for at least 2 years post-pregnancy. Our data provide the first evidence that pregnancy confers long-lasting changes in a woman's brain.

Consultations for work related low back pain in Argentina.

OBJECTIVE: Low back pain (LBP) is a common cause of disability among people of working age. We investigated the incidence of consultation for work related LBP and of work absence, and determined the prevalence of continued work disability due to LBP in Argentina. METHODS: Our study population comprised 139,740 fulltime workers (mean age 34.4 yrs, range 17-79). An episode of work related LBP was defined as patient consulting because of acute LBP while at work or while traveling to/from work. RESULTS: In a 6 month period 360 episodes of acute LBP were reported in 69,329 worker-years of exposure to risk; thus the episode incidence rate was 5.2/1000 worker-years. This was the third most frequent work related injury. Twenty-one patients (5.8% of episodes) were lost to followup. Those with LBP were significantly older than the population at risk (p < 0.001) and were predominantly men (p < 0.001). In 244 episodes (72%) pain onset was related to heavy physical work and in 46 (13.6%) it followed trauma to the back. Surgery was performed in 9 (2.7%) cases. In total, 322 (98%) patients were absent beyond the day of the injury (median number of days of work absence, 7 days; range 0-422 days). Surgical patients lost significantly more days of work (p < 0.01). Seven patients (2%) remained off work more than 180 days: 2 were declared disabled, 3 moved to lighter jobs, and only 2 (28.5%) returned to their previous job. CONCLUSION: The incidence of consultation for work related LBP was 5.2/1000 worker-years. This was the third most frequent work related injury. Most patients had some work absenteeism. Surgery did not shorten recovery times. Only a minority of patients off work for 6 months or more were able to return to their previous job.