A groundbreaking study has provided the first detailed map of how a woman’s brain changes throughout pregnancy.

Led by neuroscientist Liz Chrastil, the research shows that the transition to motherhood affects nearly every part of the brain. Although the study initially focuses on one individual, it marks the beginning of a significant international research project aimed at examining the brains of hundreds of women.

“It’s been a very long journey,” a co-author of the paper published Monday in Nature Neuroscience, Ms. Chrastil, said, the Associated Press reported. “We did 26 scans before, during, and after pregnancy and found some really remarkable things.”

The study observed more than 80 percent of the brain regions, noting reductions in the volume of gray matter — areas responsible for thinking. This reduction averages about 4 percent, similar to changes seen during puberty.

Contrary to what might be expected, less gray matter is not necessarily negative. Researchers suggest it likely reflects the fine-tuning of neural circuits to prepare for motherhood.

Ms. Chrastil, who was 38 years old and working at the University of California, Irvine, was monitored from shortly before she became pregnant through in vitro fertilization. Throughout her pregnancy and for two years postpartum, the team conducted MRI brain scans and blood tests, observing changes as sex hormones like estrogen fluctuated. Some changes persisted beyond pregnancy.

The research team, in partnership with collaborators in Spain, is advancing with the larger Maternal Brain Project. Supported by the Ann S. Bowers Women’s Brain Health Initiative and the Chan Zuckerberg Initiative, the project aims to gather data from numerous women. This data could potentially predict conditions like postpartum depression before they manifest.