There are moments in “Earth Mama,” a drama about motherhood at its most fragile, when the movie’s quiet intensity seems to settle in your chest, as if a heavy stone had been placed over your heart. Written and directed by Savanah Leaf — this is her feature debut — the film is intimate, modestly scaled and often so outwardly unassuming that you might not at first notice its artistry. It also features one of the most expressive scenes that I’ve seen all year, one that reveals a world of heartache with a single camera movement.

Leaf eases you into the movie, which centers on Gia (a lovely Tia Nomore), a pregnant single mother in recovery with two kids in foster care. In tight, precise scenes, Leaf sketches in Gia’s life, its uncertain horizons and crushing limitations. Gia lives in the Bay Area, where she shares an apartment with her sister, an elusive figure in her life, and works in a mall portrait studio. Mostly, Gia struggles to get her kids back, a time-consuming process that involves a reunification program in which she’s constantly monitored.

Snippets of Gia’s history emerge throughout “Earth Mama,” but much remains unsaid and unexplained. These include the kinds of biographical and sociological details that can turn similarly themed movies into lectures, viewers into voyeurs and protagonists into object lessons. By focusing instead on Gia’s existential reality — her habits, the pleasure she gets from her job, the awkwardness of her gait — Leaf humanizes her. It’s very moving, and adamantly political.