For generations of women the contraceptive pill has provided a means to a previously unimaginable sexual freedom. In Germany alone, 6.8 million women take a contraceptive pill. Taken correctly, the pill is over 99 percent effective at preventing pregnancy. But with some brands of the contraceptive pill comes the risk of potentially deadly side effects.

On Thursday, a court case against German pharmaceutical giant Bayer will open in the southern German town of Waldshut-Tiengen. The law suit was first filed in May 2011 by German native Felicitas Rohrer. The former veterinary student is suing Bayer for 200,000 euros ($220,000).

The 31-year-old claims she suffered a double pulmonary embolism as a result of taking Bayer's Yasminelle contraceptive pill, which uses the hormone drospirenone. An embolism is caused by a blot clot obstructing the circulatory system.

'No existing condition'

In 2009, Rohrer, who was 25 at the time, suddenly collapsed and her heart stopped beating for 20 minutes. In emergency open-heart surgery, doctors found huge blood clots blocking the main artery to her lung.

"I didn't have a bleeding disorder, any pre-existing conditions, or any cases of illness in the family. I've never smoked, I'm not overweight and I've always exercised," Rohrer wrote on her website.

After finding no alternative explanation, doctors pointed the finger at Bayer's pill, which Rohrer had been taking for eight months when she collapsed. Since her surgery six years ago, Rohrer has had to take an anti-coagulant which reduces her chances of conceiving a child.

Rohrer's case will be the first of its kind in Germany, but in the US, such lawsuits are far from unheard of. Bayer has already had to pay out $1.9 billion in compensation in 9,000 cases of alleged side effects in the US. In 2014 alone, the company paid out 768 million euros in cases connected with with its Yasmin contraception range, which includes Yaz, Yasmin and Yasminelle.

Studies find increased risk

According to several recent studies, birth control pills containing drospirenone, such as Bayer's Yasmin range or Jenapharm's Aida and Petibelle, were found to increase the risk of an embolism or thrombosis by up to three times compared to previous generations of contraceptive pill.

Researchers in a study that assessed the data of 1.6 million Danish women who took a drospirenone contraceptive pill for several years, also found that the risk of a heart attack or stroke was higher in these women than those using a non-hormonal method of contraception.

Germany's Federal Institute for Drugs and Medical Devices (BfArM) also said they received reports from 478 women in the last 15 years who suffered from thrombosis and were also taking a contraceptive pill containing drospirenone. Sixteen of the suspected cases resulted in death.

'Positive user risk profile'

Despite the studies, Bayer insists that its contraceptive pills are safe when taken correctly. In an interview with DW, Bayer's spokesperson for women's health, Dr Michael Diehl, said that all of the company's "combined oral contraceptives, even those containing drospirenone, have a positive user risk profile, when they're taken as indicated."

Diehl also highlighted that each prescription is based on an individual assessment of risk factors and personal health. "Before a modern, low-dose combined oral contraceptive is prescribed, a doctor and patient should have a detailed conversation about personal or family risk factors, such as smoking, obesity and thrombosis in the family," he told DW.

'Aesthetic' appeal

In a report released last year by one of Germany's leading public health insurers, the Techniker Krankenkasse, pharmacologist Gerd Glaeske criticized doctors and the pharmaceutical industry for the lack of information about Bayer's Yasmin range.

It is "the first pill that has a very clear marketing angle on beauty and well-being," he argued, that opened the way for claims that contraceptive pills are effective in fighting acne.

"Due to Yasmin's anti-water-retention effects, patients are less likely to gain weight," Glaeske added.

Calls for a ban

Following her surgery, Rohrer founded a self-help group that campaigns for the pharmaceutical company to withdraw birth control containing drospirenone from the shelves.

If the campaign group were successful in banning drospirenone contraception, it wouldn't be the first time that Bayer had discontinued one of their birth control products. In neighboring France last year, the firm was forced to end sales of their acne treatment Diane-35 after four thrombosis deaths were linked to the medication.

In that case, however, Bayer had only officially approved the hormone drug to be taken to treat acne, but many doctors prescribed it instead as a contraceptive pill. After a reassessment by the European Medicine Agency, the drug was put back on sale.

While Bayer begins its legal battle on home turf on Thursday across the pond in the US, the drug company will also face a growing number of compensation law suits from women who claim its contraceptive implant Essure caused pain and severe bleeding.