The authors of the new paper used magnetic resonance imaging to track changes in the structure of the brain's gray matter in 25 women who were pregnant for the first time. Their brains were scanned before pregnancy and after childbirth (after different periods of time: from three weeks to several months). The analysis also included 20 nulliparous, non-pregnant women and, to exclude the influence of parenthood (and not specifically pregnancy), 19 men who became fathers for the first time and 17 men without children. All of these groups underwent brain scans at the same time intervals as the test group of pregnant women.