Why you should avoid YOGA in pregnancy: 35-year-old expectant mother temporarily lost vision in her eye while doing a downward pose

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It's long been adored by celebrities - but prenatal yoga isn't as harmless as Gwyneth Paltrow, Jessica Alba and Sienna Miller would have you believe.

A new case report reveals a possible danger for expectant mothers who choose to attend trendy yoga classes to keep fit and healthy.

A 35-year-old pregnant woman experienced a few weeks of vision loss - caused by straining as she stretched into a downward pose.

The difficult position, which sees a rush of blood to the head, was responsible for her valsalva retinopathy (VR), doctors claim.

They said the condition, which causes floaters in the eyes and temporarily affects vision, is usually associated with an episode of straining.

However, they warned the increased pressure in the form of practising the ancient Indian science could also trigger the bizarre symptoms.

A new case report reveals a possible danger for expectant mothers who choose to attend trendy yoga classes to keep fit and healthy

Writing in the BMJ Case Reports, doctors treating the patient, believed to be from Leicester, described it as an 'unusual case'

They said: 'We present an unusual case of VR in a pregnant woman after yoga. To our knowledge, it has not been reported in the literature in association with yoga.'

The doctors added that certain yoga exercises, such as pranayama - controlled breathing, have been linked to VR in medical literature.

But this case involved no breathing techniques, and was solely caused by the yoga position the woman attempted. 

How is the condition normally caused? 

Most often, this bizarre condition occurs during labour - where the severe strains to push out a child causes the same response.

Other triggers in pregnant women include vomiting, stooling, heavy lifting and labour. But it can also result from fairly innocuous actions.

It most commonly strikes due to extreme abdominal pressure, causing tiny blood vessels in the eyes to rupture. 

It is unsure where the patient attended her class, but the VR symptoms occurred almost immediately after striking the pose.

What were her symptoms? 

She was rushed to the A&E department at Leicester Royal Infirmary at 27 weeks gestation with a painless loss of vision.

Doctors also noticed a large floater in her left eye - which are often dismissed as harmless but can be a sign of something more sinister.

The patient revealed the symptoms were triggered following a head down posture, when her head was below her bottom.

After five months of follow-up, this woman had undergone a normal delivery and her haemorrhages and vision loss had resolved.

Doctors said that prognosis of the strange condition is 'variable', but most cases report 'excellent' outcomes.

Is yoga safe during pregnancy? 

According to NHS guidelines, it's safe to keep up your normal level of exercise in pregnancy whether that's yoga, running or dancing.

The more active and fit you are during pregnancy, the easier it will be for you to adapt to your changing shape and weight gain. 

It will also help you to cope with labour and get back into shape after the birth, experts say.

However, pregnant women are advised against contact sports such as judo, scuba diving and exercising at altitude.