The Birthing Brain: A Lacuna in Neuroscience

Hormones and Behavior, 2015

Early mother-infant relationships play important roles in infants' optimal development. New mothers undergo neurobiological changes that support developing mother-infant relationships regardless of great individual differences in those relationships. In this article, we review the neural plasticity in human mothers' brains based on functional magnetic resonance imaging (fMRI) studies. First, we review the neural circuits that are involved in establishing and maintaining mother-infant relationships. Second, we discuss early postpartum factors (e.g., birth and feeding methods, hormones, and parental sensitivity) that are associated with individual differences in maternal brain neuroplasticity. Third, we discuss abnormal changes in the maternal brain related to psychopathology (i.e., postpartum depression, posttraumatic stress disorder, substance abuse) and potential brain remodeling associated with interventions. Last, we highlight potentially important future research directions to better understand normative changes in the maternal brain and risks for abnormal changes that may disrupt early mother-infant relationships.

2016

 Abstract•  Introduction•  Results•  Discussion•  Methods•  References•  Acknowledgments•  Author information•  Supplementary information 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 inbetween 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, suggestiv...

nature neurOSCIenCe advance online publication a r t I C l e S Most women undergo pregnancy at least once in their lives, yet little is known of how this process affects the human brain. Mammalian pregnancy involves radical physiological and physical adaptations orchestrated by endocrine changes 1 . During pregnancy, there are unparalleled surges of sex steroid hormones, including, for instance, an increase in progesterone of 10-15 fold relative to luteal phase levels and a flood of estrogens that typically exceeds the estrogen exposure of a woman's entire nonpregnant life 2 . Sex steroid hormones are known to act as an important regulator of neuronal morphology and number 3 . Not surprisingly, other endocrine events involving less extreme and rapid fluctuations in hormone levels than pregnancy are known to render structural and functional alterations in the human brain. The production of gonadal sex steroid hormones during puberty regulates an extensive reorganization of the brain 4-6 , and neural alterations have also been observed in response to even subtle changes in endogenous or exogenous steroid hormone levels later in life 7-9 .

Behavioral Neuroscience, 2010

Animal studies suggest that structural changes occur in the maternal brain during the early postpartum period in regions such as the hypothalamus, amygdala, parietal lobe, and prefrontal cortex and such changes are related to the expression of maternal behaviors. In an attempt to explore this in humans, we conducted a prospective longitudinal study to examine gray matter changes using voxel-based morphometry on high resolution magnetic resonance images of mothers' brains at two time points: 2-4 weeks postpartum and 3-4 months postpartum. Comparing gray matter volumes across these two time points, we found increases in gray matter volume of the prefrontal cortex, parietal lobes, and midbrain areas. Increased gray matter volume in the midbrain including the hypothalamus, substantia nigra, and amygdala was associated with maternal positive perception of her baby. These results suggest that the first months of motherhood in humans are accompanied by structural changes in brain regions implicated in maternal motivation and behaviors.

Brain Sciences, 2021

Neuroimaging researchers commonly assume that the brain of a mother is comparable to that of a nulliparous woman. However, pregnancy leads to pronounced gray matter volume reductions in the mother’s brain, which have been associated with maternal attachment towards the baby. Beyond two years postpartum, no study has explored whether these brain changes are maintained or instead return to pre-pregnancy levels. The present study tested whether gray matter volume reductions detected in primiparous women are still present six years after parturition. Using data from a unique, prospective neuroimaging study, we compared the gray matter volume of 25 primiparous and 22 nulliparous women across three sessions: before conception (n = 25/22), during the first months of postpartum (n = 25/21), and at six years after parturition (n = 7/5). We found that most of the pregnancy-induced gray matter volume reductions persist six years after parturition (classifying women as having been pregnant or n...

Cerebral Cortex, 2021

There is growing evidence that pregnancy may have a significant impact on the maternal brain, causing changes in its structure. To investigate the patterns of these changes, we compared nulliparous women (n = 40) with a group of primiparous women (n = 40) and multiparous mothers (n = 37) within 1–4 days postpartum, using voxel-based and surface-based morphometry (SBM). Compared with the nulliparous women, the young mothers showed decreases in gray matter volume in the bilateral hippocampus/amygdala, the orbitofrontal/subgenual prefrontal area, the right superior temporal gyrus and insula, and the cerebellum. These pregnancy-related changes in brain structure did not predict the quality of mother–infant attachment at either 3 or 12 weeks postpartum nor were they more pronounced among the multiparous women. SBM analyses showed significant cortical thinning especially in the frontal and parietal cortices, with the parietal cortical thinning likely potentiated by multiple pregnancies. W...

Plots of the remaining clusters For the remaining clusters not indicated in the main figures (the left inferior orbitofrontal and the left middle frontal cluster, see Table 1), this figure depicts the (a) slice overlays,(b) plots representing the mean signal from the smoothed normalized jacobian difference images of the PRE and POST session, and (c) plots representing the mean (M±S.E.M.) signal change at each POST session relative to the pre-pregnancy baseline. F CTR =nulliparous control women, F PRG =women who were pregnant and transitioned into primiparity in-between sessions, Inf.= Inferior, Mid.= Middle, L=Left.

Human Brain Mapping

Psychoneuroendocrinology, 2019

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.