Ms. Suzuki has chosen not to breast-feed and that, too, has drawn criticism. “It’s easiest to not say anything when I get these types of comments, and many people don’t realize these are just their own beliefs,” she said. “I try very hard to let them know my child is fine and we’re doing very well.

“Unless I reassure them, new mothers following my footsteps will also have to endure this criticism.”

Despite its status as the world’s third-largest economy, Japan lags far behind other countries when it comes to the participation of women in politics. According to data from the nonprofit Inter-Parliamentary Union, China, the United States and South Korea are all ahead of Japan. It ranks 158 out of 193 countries, with women representing just 10.1 percent of its lower house, the House of Representatives. (In the upper house, the House of Councillors, women make up 20 percent.)

It’s no surprise, then, that the number of women who have become mothers while holding political office is minuscule.

“They are a novelty in Japan,” said Hiroko Nagano, the founder of a Facebook group called Network for Politicians Giving Birth (While in Office). Ms. Nagano is an assemblywoman from Tokyo’s City of Toshima district.