A Louisiana man has filed a lawsuit after claiming that his ex-girlfriend stole his frozen sperm from a clinic and used it to get pregnant.

Smoking, alcohol consumption, drugs and tight underpants have very little to do with lower sperm count, according to a new report.

Scientists from the Universities of Manchester and the University of Sheffield have found that an unhealthy lifestyle such as consuming alcohol, smoking and drugs has very little impact on sperm quality than previously estimated.

Previously, researchers had stated that smoking, alcohol consumption and recreational drug use, as well as the risks of being overweight and wearing tight underwear have a major effect on sperm quality. They claimed people who smoke and consume alcohol are likely to have lower swimming sperm.

Scientists have now found that an unhealthy lifestyle has minimal impact on sperm quality. The discovery was made when they analysed sperm quality of 2,249 men from 14 fertility clinics around the UK.

During the study, scientists analysed 2,249 men's sperm quality from 14 fertility clinics around the UK. The participants were asked to fill out detailed questionnaires about their lifestyle. They found that among 2,249 men, 939 men had ejaculated low numbers of swimming sperm, whereas the other 1,310 men had produced higher numbers of swimming sperm.

The study revealed that men who ejaculated low numbers of swimming sperm were 2.5 times more likely to have had testicular surgery and 1.3 times more likely to be in manual work, not wearing boxer shorts, or not had a previous conception.

Surprisingly, men's use of recreational drugs, tobacco and alcohol, as well as their weight measured by their body mass index (BMI), had little effect on the sperm quality.

"The higher risk we found in manual workers is consistent with earlier findings that chemicals at work could affect sperm and that men should continue to keep work exposures as low as possible," said Professor Nicola Cherry, scientist at the University of Manchester, in a statement.

"Despite lifestyle choices being important for other aspects of our health, our results suggest that many lifestyle choices probably have little influence on how many swimming sperm they ejaculate. For example, whether the man was a current smoker or not was of little importance. The proportion of men who had low numbers of swimming sperm was similar whether they had never been a smoker or a smoker who was currently smoking more than 20 cigarettes a day. Similarly, there was little evidence of any risk associated with alcohol consumption," said Dr Andrew Povey, scientist at the University of Manchester's School of Community Based Medicine, in a statement.

Even though the study says that an unhealthy lifestyle has very less effect on the swimming sperm, scientists believe it could affect the size and shape of sperm (sperm morphology) or the quality of the DNA contained in the sperm head.

However, further study needs to done in these aspects to know about the affects of unhealthy lifestyle on sperm quality.

"In spite of our results, it's important that men continue to follow sensible health advice and watch their weight, stop smoking and drink alcohol within sensible limits. But there is no need for them to become monks just because they want to be a dad. Although if they are a fan of tight Y-fronts, then switching underpants to something a bit looser for a few months might be a good idea," said Dr Allan Pacey, scientist at the University of Sheffield, in a statement.