text: sleep patterns11. These factors could have a role in the brain changes 
  observed here, with some driving neurobiological changes and others, 
  like water retention, potentially affecting MRI-based measurements. 
  Note that, although cortical reductions in GMV over gestation were 
  stable across analyses, accounting for QC measures influenced the 
  magnitude and location of these results. These metrics all fell within 
  the standard range, but there may be meaningful reductions in signal 
  that accompany volumetric reductions (for example, increased CSF 
  and decreased GM)—a methodological nuance that goes beyond the 
  scope of this resource study. Ultimately, identifying the shared and 
  unique contributions of these factors to the neuroanatomical changes 
  that unfold across gestation warrants further investigation. Deeply 
  phenotyping a large and diverse cohort of women across pregnancy will 
  open up new avenues of exploration, for example, allowing research- 
  ers to link blood-based proteomic signatures to pregnancy outcomes; 
  deploying wearable devices to monitor changes in sleep, cognition and 
  mood; and probing the broader social and environmental determinants 
  of maternal health27.  overlook the full range of changes that unfold within the gestational 
  window, and underrepresent the brain’s metamorphosis during preg- 
  nancy. Furthermore, although observed changes were largely global, 
  some regions displayed notable stability (for example, extrastriate cor- 
  tex). The subcortical region that displayed the strongest relationship 
  with gestation week was the ventral diencephalon, which encompasses 
  the hypothalamus and subsequent medial preoptic area and paraven- 
  tricular nucleus—structures critical for inducing maternal behavior12,16. 
  The hippocampus exhibited a reduction in volume across gestation, 
  and with higher spatial resolution, this reduction was revealed to be 
  driven by changes in CA1 and CA2/CA3 subfield volumes, while other 
  hippocampal subfields remained stable. Adjacent PHC within the 
  MTL also exhibited volume reduction across gestation. While our hip- 
  pocampal findings are consistent with pre/post studies of pregnancy13, 
  the precision lens applied within gestation revealed the nonlinear 
  nature of this reduction. Recapitulating and clarifying these region- 
  ally specific patterns of volume change throughout the MTL merits 
  further investigation. 