The genetics survey conducted in Japan by the Atomic Bomb Casualty Commission (ABCC) was the largest health survey conducted during the post-war occupation. The purpose of this study was to examine the collaboration between ABCC scientists and Japanese midwives in the genetics survey by reviewing the 1951 ABCC minutes. ABCC scientists and midwives routinely communicated, with scientists considering questions and proposals from midwives throughout the survey. The ABCC scientists adjusted their approach based on these proposals, taking into account the detailed opinions of midwives and their representation of the mothersʼ feelings. The midwivesʼ delivery reports were essential for the success of the genetics survey, and they advocated for and represented the feelings of the participating mothers and families. Thus, the midwives were able to voice their opinions freely to ABCC scientists as their equals. ABCC scientists reciprocated by making efforts to build close collaborative relationships with midwives by creating a system that made it easy for midwives to speak their minds.