pill for five years when she was told it was no longer safe for her to do so. She was in her mid-twenties and had started getting migraines with aura, which are associated with a higher risk of stroke on the pill. Swapping to the progesterone-only pill made her feel terrible: "I bled every day for two months, so they upped my dose," she recalls. "The higher the dose, the worse I felt. I had symptoms of depression: I had no energy, wanted to stay in bed, and felt really emotional."

It was after hearing about Natural Cycles' certification that Davis decided to try it, and met her partner, who works in insurance, shortly after. By summer 2017, she had been using the app for around seven months andhad reached the point when she had more green days than red ones. She inputted her temperature around 25 days a month and avoided unprotected sex when advised.

In July, she went to visit her new boyfriend in Amsterdam, where he was working. "He immediately said my breasts looked bigger," she recalls. "I ordered a beer and couldn't drink it; it didn't taste right." She was pregnant.

"I cried for two weeks. But both of us have always wanted a family and thought we would one day do it together."

Given her age and a diagnosis of endometriosis, Davis and her partner decided to continue with the pregnancy - he has now moved in with her and their baby is due on June 16.

Natural Cycles, which doesn't claim its method is