Couples seeking fertility treatment are being sold "add ons" by clinics despite little evidence some of them work, a watchdog has warned.
The Human Fertilisation and Embryology Authority (HFEA), which regulates IVF and fertility clinics, said it was planning to ensure patients had access to accurate information about a range of "extras" so they could make informed decisions.
Couples are being increasingly sold treatments aimed at boosting IVF success, including immune system-suppressing drugs, pre-implantation testing and time-lapse photography.
The warning comes following a series of interviews with experts published by The Independent, with some claiming clinics were handing out "expensive, potentially harmful stuff like Smarties", or announcing breakthroughs that were closer to marketing "hype".
One said that half of the people treated did not actually need any help to have a baby.
The HFEA's chairwoman Sally Cheshire said in a statement: "Although the vast majority of clinics provide excellent care for fertility patients, we are becoming increasingly concerned about IVF treatment 'add-ons' without a strong evidence base being offered at some clinics.
"We know from talking to patients that they can find navigating the IVF process difficult and the offer of 'add-ons' can increase their confusion, and the cost of their treatment.
"Patients are often not sure whether they need the additional treatments, but worry that they could regret not making every attempt they can to get pregnant."
She said the HFEA was now working with scientists and the industry to "provide accurate and easy-to-understand information about these new treatments".
In an interview with The Independent, Cambridge University immunologist Professor Ashley Moffett questioned the idea that a foetus might be attacked by its mother's body because half the unborn baby's DNA comes from the father.
"That's a very attractive idea, but it's actually not correct. But it's become firmly embedded and it's extremely hard to dislodge it, even among scientists," she said.
"There's certainly no evidence that it [immune-suppression] does any good and there is the potential that it can do harm because these treatments are immunosuppressive."
She said one woman given immunosuppressant drugs by a private clinic became pregnant, but also seriously ill with a fungal infection. After the infection got into her bloodstream, she "lost the baby as a result quite late in the pregnancy".
She added: "I think these women are quite obviously, one understands, desperate, desperate and they will try anything."
Yacoub Khalaf, director of the assisted conception unit of at Guy's and St Thomas' Hospital in London, told The Independent that some of those working in private fertility clinics were "very decent and honest people".
But he added: "At best, patients are subject to exploitation; at worst, patients are being subjected to harm.
"All of this needs to be subjected to rigorous checks - and a reality check among the providers and the users."
Mr Khalaf said some fertility clinic staff were simply putting "two and two together" about treatments that appeared to show signs of success without waiting for scientific proof.
He said there might be a small number of patients who would benefit from such treatments, but this was "not a recipe to just dish out expensive, potentially harmful stuff like Smarties".
"Some patients, through their use of expensive, unproven medication, could be deprived of the financial resilience to try again," he added
Professor Martin Johnson, emeritus professor of reproductive sciences at Cambridge University and joint senior editor of the journal Reproductive BioMedicine and Society, said there was "a lack of scientific rigour" behind some fertility clinic techniques.
He said: "What it means is the treatment could be making their situation worse and certainly not improving it - and is costing them money. It's all about anecdotal evidence or no objective evidence."
Dr John Parsons, founder and former director of King's College Hospital's assisted conception unit, said: "I genuinely believe at least 50% of the people who got pregnant didn't need our help."
Professor Adam Balen, chairman of the British Fertility Society - which speaks on behalf of the industry, said: " Clinics have to be transparent and be open and provide appropriate information about exactly what it is they are offering and provide their own statistics as to the potential prospects of success.
"All of these treatments have been tested around the world and have been studied in clinical trials - every single one. None have been shown to do harm."