Molly Cruit attached a small device to her pregnant belly, and a few minutes later, a graph on her smartphone suddenly spiked.

“Oh my god!” the 38-year-old Portrero Hill resident exclaimed.

She was having a contraction. But without the device, a small sensor she stuck to her belly called Bloomlife, and its corresponding app, she probably would have just passed the faint tightness in her belly off as nothing, she said.

Bloomlife is a digital pregnancy wearable that helps women track the frequency and duration of their labor contractions. On Wednesday, the San Francisco startup announced that the product had completed trials and is commercially available. An update, expected this year, will be able to track the baby’s movements, heart rate and position, and the mother’s stress levels.