text: As a further test of the robustness of the dataset, we ran QC assess- 
  ments on all T1w images using the IQMs pipeline64 from MRIQC (ver- 
  sion 23.1). Assessments of interest included (1) coefficient of joint 
  variation (CJV), (2) signal-to-noise ratio for gray matter (SNR) and (3) 
  contrast-to-noise ratios (CNR). All QC metrics fell within expected 
  standard ranges65 (Supplementary Fig. 4b–d). Although relationships 
  existed between gestation week and QC measures (CJV,*r*= 0.70 and 
  *P*< 0.001; SNR and CNR,*r*= −0.83 and*P*< 0.001), including these vari- 
  ables in the regression models did not detract from our finding sug- 
  gesting cortical GMV reductions occur over gestation, especially within 
  regions belonging to attention and somatosensory networks (Supple- 
  mentary Fig. 5). When looking across all MRIQC outputs, discrepancies 
  were noted in session seven (gestation week nine, first trimester). 
  Removing this day from the analyses only strengthened observed 
  relationships between cortical volume and gestation; however, for 
  completeness, data from this day is included in the main findings. 
  These QC outputs for each session of the experiment can be found 
  in Supplementary Data 1. Finally, we used FreeSurfer’s Eueler num- 
  ber to evaluate a field-standard quantitative assessment of each T1w 
  structural image66. We observed no significant relationships between 
  the Euler number and gestation week or summary brain metrics. A 
  discrepancy (for example, two s.d. below average) was noted in session 
  eight; however, again, removing this session did not detract from our 
  main findings showing reductions in GMV over gestation. 