A saliva-based fertility tracker has received regulatory approval for use as a contraceptive in Europe. Developed by Berlin-based startup Inne, the at-home testing device — called the “Minilab” — tracks daily changes in progesterone levels, a hormone that plays a key role in regulating the menstrual cycle. It’s billed as a non-invasive alternative to hormonal birth control methods like the pill — and early tests have shown promising results. A year-long clinical study involving 300 women over 1,...