Clue, an app that tracks women’s menstrual cycles and predicts when they may be in pain, has raised $20 million, led by the venture capital (VC) arm of Finnish network equipment maker Nokia . Users can input details about their menstrual cycles, then the algorithm will learn and can predict when a woman is most fertile and when they may be in pain. Its website states that it can help if you “want to get pregnant, be prepared for your next period or understand your mood swings.” The app was launched in mid-2013 and earlier this year reported about 5 million monthly active users. It hasn’t disclosed the latest figures, but Clue founder Ida Tin said the user base is “growing very nicely.” Nokia Growth Partners, the VC arm of Nokia, led the round with existing investors Union Square Ventures, Mosaic Ventures, Brigitte Mohn and Christophe Maire also participating. Clue could be of strategic importance to Nokia which has been trying to expand into new areas such as virtual reality and health care. Earlier this year, Nokia announced the acquisition of fitness wearable gadget maker Withings for 170 million euros (US$181.35 million). Withings Chief Executive Cedric Hutchings became head of Nokia’s digital health business with the company citing its strength in “preventive health and patient care”. This is where German start-up Clue could feed in. Tin said that initial discussions regarding how Clue could work with Withings has been discussed but nothing has been decided. “A company like Withings is interesting. We need to meet the parents first so we haven’t started connecting to other portfolio companies. We have talked about it (working together), I’m sure it will happen but nothing concrete yet,” Tin told CNBC in a phone interview. Clue faces competition from other similar apps such a Glow in the U.S. which also tracks women’s menstrual cycle providing data on ovulation and mood. Clue also is currently not making money. The company’s chief executive said that it has been focusing on growing its user base and is now making plans to open up revenue streams. “We have many ideas, we will start experimenting this year,” Tin told CNBC, saying that she could not give specific details. “We have chosen to be strictly consumer facing, at this point we want to focus on business models that are consumer facing. We are very much a trust-based service, people trust us with very personal information. By having a consumer facing business model, people can understand how we make money. If it’s a business model that is invisible, they might assume we are selling data, which we aren’t doing.” The U.S. is Clue’s biggest market and the start-up is continuing to expand into new regions including Japan and India where it has launched local-language versions of its app. Tin said that Clue can reach a worldwide audience. “There is a huge social movement around menstrual health and mobile growth is exploding, so all these things combined make these markets interesting. We are addressing a real need for people and that need is truly global,” Tin told CNBC.