The Impact of Pregnancy and Childbirth on Gamma-Aminobutyric Acid Neuronal Function

by Dominguez, Jennifer Estrella

Our present knowledge of the neuroendocrine changes associated with pregnancy and parturition is based primarily upon peripheral measures of ovarian hormones. Despite numerous investigations from productive laboratories, the impact of these dramatic hormonal fluctuations on brain function and their role in mediating normal maternal behavior or common postpartum mood disturbances has not been well elucidated. We hypothesized that occipital cortical gamma-aminobutryic acid (GABA) concentrations would be reduced in healthy, postpartum women compared to regularly menstruating, non-postpartum women in the follicular phase of their menstrual cycles, and that a gradual increasing trend in GABA would be seen across the puerperium. We also hypothesized that occipital cortical GABA concentrations would differ between non-depressed postpartum women with a personal or family history of a mood or anxiety disorder compared to healthy parturient women with no such history. We used the novel neuroimaging technology, proton magnetic resonance spectroscopy (1H-MRS), to investigate the effect of the early and extended puerperium in healthy, postpartum women (n =12), as well as at-risk postpartum women (n = 5) with a personal or family history of mood or anxiety disorder, on occipital cortex GABA concentrations. We compared these measurements with those from healthy, nonpuerperal women (n = 14) in the follicular phase of the menstrual cycle. We found no significant differences in GABA concentrations in the early postpartum period in either healthy, postpartum women or at-risk, postpartum women as compared to follicular phase controls. GABA concentrations remained stable over time in each group. There was a trend towards greater variations in GABA over time in the at-risk group as compared to follicular controls, however this did not reach statistical significance (t=-1.84, df=13, p=0.088), and these findings must be interpreted cautiously due to the small sample size with repeated measures in the at-risk group (n = 3). Contrary to our hypotheses, this study does not support a difference in GABA concentrations measured in the occipital cortex using 1H-MRS between healthy or at-risk postpartum women, and follicular phase, healthy controls. It does show a trend, however, which suggests that further studies may show evidence of greater GABA dysregulation in at-risk postpartum women compared to follicular phase controls, although these findings must be interpreted cautiously due to the small sample size.