By Phil Kemp
Five Live Report
The chances of successful IVF treatment on the NHS are lowered because doctors do not always see patients at the best time, a BBC investigation has found.
The timing of egg collection and transfer back is key
The key moments in an IVF cycle are when eggs are collected and when the fertilised eggs are transferred back to the womb.
The top five clinics carry out these procedures at least five days a week.
But more than half of NHS clinics that responded to a Five Live Report survey did so fewer than four days a week.
Some only did it one or two days a week.
Kavita, 38, from London has been trying for a baby for eight years, during which time she has had treatment both privately and on the NHS.
She said her private treatment was always more likely to result in pregnancy.
She said: "They are waiting to see the optimum moment for when it's best to collect the eggs and monitoring the condition.
"I just remember with the NHS, it was very geared around when they could fit me in rather that when it was appropriate."
After more private treatment, Kavita has now discovered that even with IVF treatment, she is unlikely to conceive naturally.
But this was something that wasn't explained to her before her NHS treatment.
She said: "I just felt that the whole process was a complete and utter waste of time.
"All one is asking is for consideration to be given to what is appropriate for me and is the treatment tailored to my needs from a medical point of view?
"At no time could I say that that was the case."
Laurence Shaw is deputy medical director at the private clinic, the Bridge Centre in London.
Until 2005, he was an IVF specialist with the NHS, where he only had time to collect eggs one morning a week.
He said this was typical of the pressures other units are facing.
"The vast bulk of units up and down the country are very similar to the one I used to work in.
"They may be only free to do an egg collection or an embryo transfer on one or two days of the week."
Having the flexibility both to collect eggs and transfer embryos back into a woman's womb at the optimum moment, he said, could make a significant difference to the patient's chances of conceiving.
"This is a biological process and the more we can respond to the biological response the better.
"You are more likely to improve your pregnancy rates if you can adapt to the needs of the particular patient."
According to figures from the regulator, the Human Fertilisation and Embryology Authority, IVF clinic success rates range from around 50% for the best performing clinics to 10% for the worst.
Clare Brown, from the patient group Infertility Network UK, said the impact week-long egg collection and embryo transfer procedures have was an area the NHS needed to look at.
"I would urge more research into what can improve success rates.
"For the sake of patients and to give them the best possible chance, we need to look into this very carefully."
5live Report: NHS Baby Blues can be heard at 1100BST and 1900BST on Sunday 12 August or afterwards at the 5live Report website.