One third of women can’t function normally during their period, a survey by the Radboud teaching hospital in Nijmegen among 42,000 women has found.

Half of women who experience problems related to menstruation don’t talk about it, head researcher and gynaecologist Bertho Nieboer said.

‘They hide the fact that they have not been able to do certain things because of period pain, for instance. That means a condition may go untreated,’ he told broadcaster NOS.  A painful condition like endometriosis, or tissue growth outside the uterus, could go undetected and cause infertility, he warned.

The most frequently mentioned problems by women are severe stomach ache, psychological problems, tiredness and back ache, Nieboer said.

It is important women discuss the problem, gynaecologist Joke Schutte said. ‘You really don’t have to bring up your period pain at every birthday party you go to but if you are really suffering then that is not normal and you need to speak out,’ the broadcaster quotes her as saying.

The survey, the biggest of its kind, may not represent all women in the Netherlands because it was conducted online and this may have caused selection bias. In other words those not experiencing problems less likely to participate in a survey, but it gives a good indication of the scale of the problems, the researchers said.