Marrying a Jewish man — and having Jewish children — wasn’t a top priority for Irina Barskaya. Despite pressure from her mother and her older sister, Ms. Barskaya, a 33-year-old hair and makeup artist from Brooklyn, said that in her search for Mr. Right, religion was “never at the forefront.”

Oct. 7 changed her mind.

Scrolling through social media between clients at the Midwood salon where she works, Ms. Barskaya found herself in tears at reports of the Hamas attacks on Israelis, in which about 1,200 people were killed, according to the authorities. As the scale of the killings became clear in the following days, Ms. Barskaya thought of her family and friends in Israel, and felt a new resolve to reproduce with another Jew.

“There’s not a lot of us in the world,” Ms. Barskaya said. “If we don’t continue this path and journey of marrying people and having children within our religion, that could end.”

In November, Ms. Barskaya traveled to Washington, D.C., to participate in the March for Israel, in which thousands of people gathered on the National Mall to show their support for the Jewish state. She brought a homemade sign. On the front it read “Bring them home!,” referring to the hostages held in the Gaza Strip.

On the back, it read “Who’s coming home with me? #MakeJewishBabies.”

It was a joke, kind of. A dark joke in a dark moment, when political engagement for people like Ms. Barskaya has turned painfully personal. Amid an endless scroll of social media invective and atrocity, and in the face of a gnawing feeling that many things in the world are hopeless, some young American Jewish women say they are doing — or trying to do — something that is the opposite of hopeless.