(Reuters Health) - Scratching the interior of the uterus before implanting a fertilized egg into the womb does not improve the chances that it will attach and develop into a baby, according to a large study of a popular in vitro fertilization (IVF) technique that now appears to be a waste of time and money.

The method, known as endometrial scratching, involves taking a flexible tube that lets gynecologists collect tissue samples in the uterus and using it to create a small scratch in the lining of the uterus a month or so before a fertilized egg is transferred.

The scratch was supposed to somehow create inflammation or affect the immune system in a way that would make it easier for the egg to attach.

But the new randomized, controlled trial of the technique, which was performed on half of the 1,364 women included in the study, showed that unscratched women were just as likely to get pregnant and deliver a baby as those who received the scratch.

In fact, the success rates in the two groups were identical: 180 live births in the 690 women (26.1%) in the endometrial-scratch group and 176 among the 674 women (26.1%) in the control group, the study team reports in the New England Journal of Medicine.

Although the technique was unproven - earlier studies supporting its use were small or not done well - a survey in the UK, Australia and New Zealand showed that 83 percent of fertility doctors were doing it, and typically charging $200 to $500 for the futile procedure

“We would recommend that clinics stop offering this,” lead study author Sarah Lensen told Reuters Health in a telephone interview.

“This unequivocally shows there is no place for this in our practice for treating infertility patients,” Dr. Christos Coutifaris, past president of the American Society for Reproductive Medicine, told Reuters Health by phone.

Even when the researchers looked at subsets of patients who, in theory, might benefit, “there’s not even a trend” indicating that scratching improves the success rate, said Coutifaris, of the University of Pennsylvania’s Perelman School of Medicine in Philadelphia, who wasn’t involved in the study.

If nothing else, abandoning the technique will save women some pain. On a scale of 1 to 10, with 10 being the worst pain, half of the participants in the study said the scratching technique rated a 3.5 or higher, and that was after they had taken pain medication first.

The pain was so great for one woman, she went to the emergency department. Seven fainted, felt dizzy or experienced nausea after the scratch. There were two cases of excessive bleeding. The technique did not appear to cause any infections.

Lensen said the practice of endometrial scratching began around 2005 after a group of fertility doctors noticed that women who had failed previous IVF attempts seemed more likely to get pregnant after the doctors took tissue biopsies to help figure out why their fertilized eggs weren’t implanting. The idea has actually been around since the 1970s, Coutifaris noted.

The new study was done at 13 centers in five countries, with women recruited over a three-year period. For 25 percent of the volunteers, it was at least their third attempt to have a child via in vitro techniques.

The Lensen team also looked at whether scratching affected the odds of having twins, a miscarriage or a tubal pregnancy. It did not.

Nor did it matter whether the implanted embryos were fresh or had been frozen.

“Neither the days between endometrial scratch and embryo transfer nor pain during the procedure was a predictor of live birth in the endometrial-scratch group,” the researchers report. “There was also no evidence of any benefit from endometrial scratching among women in whom implantation had failed at least twice or among women in whom it had failed no more than once.”

The scratching was typically done 35 days before the embryo was transferred into the uterus, but doctors had wide latitude over the timing.

Because the study showed no benefit among women in any of the subgroups and was done at centers in different countries, “the results of this trial should be trusted,” Drs. Ben Mol of Monash University in Australia and Kurt Barnhart, also of Perleman, write in an accompanying editorial.

SOURCE: bit.ly/2FESdVv The New England Journal of Medicine, online January 23, 2019.