For someone who was told she'd never have her own biological children, 40-year-old Tracy Sant, who has an 18-month-old daughter and is now expecting a son, is doing well.
Like many other women, the former RAF pilot was turned away from fertility clinics as a matter of course because her levels of Follicular Stimulating Hormone (FSH) were considered too high.
"A well-known clinic in Wimpole Street turned me down because my FSH was 12," Sant says. "Four months later we went to another fertility centre in Cambridge. By then my FSH levels had risen to 22.
"The consultant told me this meant I was approaching the menopause and wouldn't be able to have a child naturally. Egg donation, he said, would be my only option. Well, we weren't ready to hear that and were absolutely devastated."
FSH is linked to egg quality and quantity. When levels exceed 10 to 15, it is widely believed a woman's eggs aren't good enough quality for fertilisation. There is another hitch. The IVF industry relies heavily on fertility drugs to guarantee success rates. And patients such as Sant, who have high FSH and are medically known as "poor responders", do not respond well to fertility drugs.
Yet there is now more evidence than ever to show that mild or natural-cycle IVF – which uses a woman's natural cycle and minimal or no ovary-stimulating drugs – does work for these women.
Several studies have shown this gentle approach leads to better-quality eggs and improved rates of implantation in the womb lining, exactly what women need if egg numbers and quality are hanging in the balance.
The outcome is significant. In a study at the Centre of Assisted Reproduction in Rome on "poor responders" with high FSH levels, natural-cycle IVF led to a pregnancy rate of 18 per cent each cycle in women under 35. In those aged 35 to 40, pregnancies were achieved at a rate of 11.7 per cent per cycle.
Dr Geeta Nargund, medical director of Create Health Clinic and president of the International Society for Mild Approaches in Assisted Reproduction (ISMAAR), says that might not seem like a high percentage. But it is significant when the only other option might be egg donation, she says.
"Although natural-cycle IVF success rates are lower than conventional stimulated IVF in young women with normal egg reserve, it can be equally or even more successful in older women who have high FSH and low-egg reserve," Dr Nargund says. "Also, the treatment does not upset the body's hormones, so you can fit around twice the number of treatments into the same time period."
Vitally for women with low egg reserves, mild IVF is known to lead to fewer genetic abnormalities in developing embryos. One study in Human Reproduction that compared embryo quality had to be abandoned on ethical grounds when researchers discovered that standard IVF led to almost double the rate of genetic abnormalities in embryos than those produced using low-dose IVF. Another study, also in Human Reproduction, found that low-dose IVF had double the rate of embryo implantation in the womb lining, compared with standard IVF, which required twice the number of embryos to get the same results.
"Forcing eggs to mature using high-dose medication in women with low egg reserve may not be in the best interests of egg quality," Dr Nargund says. "Instead, evidence suggests it is best to work with nature where the egg is selected naturally and matures in its own time."
Minimal or zero-drug IVF may also be better for a baby's future health. In research just published in the European Journal of Obstetrics and Gynecology, babies born using natural-cycle IVF were on average 134g heavier than those born under standard IVF regimens. This is significant because in recent years lower birth weights have been linked to an increased risk of cardiovascular and other inflammatory diseases later in life.
So why aren't more clinics offering women this treatment?
Unfortunately, there is a view that the success rates with natural-cycle IVF are so low, it is not worth bothering with. And clinics that wish to remain at the top of the Human Fertilisation and Embryology Authorities' (HFEA) league tables do not want to offer options with lower success rates.
"In patients who don't have ability to respond to medication the only option is natural IVF but the chances of success are low and that is why clinics do not encourage it," says Paul Serhall, medical director of UCL's Centre of Reproductive and Genetic Health.
But a low success rate counts for women desperate to have their own child. Sant and her husband, Andrew, certainly had the odds stacked against them. Not only did Sant have high levels of FSH, but her husband suffers from fertility problems as a result of carrying the Cystic Fibrosis gene. At Create Health, one of the few UK clinics to offer natural-cycle IVF, the couple was given a 7 per cent chance of having their own child.
The main thing for us is that our chances weren't zero," Sant says. "Because Andrew cannot produce mature sperm, my eggs had to be fertilised with ICSI. Despite this difficulty, over nine cycles of natural-cycle IVF, I got pregnant three times. The first pregnancy was lost but I became pregnant again after six attempts and gave birth to my daughter, Georgina."
Wanting a second child, the couple started trying again. Just a year after Georgina's birth, Sant got pregnant after a further three cycles of natural-cycle IVF.
Sant believes the non-drug approach helped keep her eggs healthy. "Each time I produced embryos, they were good quality and I'm sure staying away from fertility drugs helped," she says.
"I was also able to undergo nine IVF attempts in a relatively short period of time. With standard IVF you need to wait two or three months to recover. But with natural IVF, I could start a new cycle as soon as I knew the previous cycle had not worked."
Catherine Huntley, 43, turned to natural-cycle IVF at Create Health after being told by an IVF clinic that she would not be able to have her own child.
"I tried one cycle of conventional IVF at a leading IVF unit but it was abandoned because I had high FSH and I wasn't responding to the drugs," says Catherine, a writer from north London.
The doctor ruled out natural-cycle IVF as an option. "They said it is less successful than conventional IVF, so what chance would I have? I was told my only hope for a child would be through egg donation."
Huntley approached Create Health Clinic in London after reading an article about natural-cycle IVF. "At my age I had just a 5 per cent chance of a successful pregnancy," she says. "But I got pregnant after four attempts, which I thought was pretty good for someone who had been told to 'forget it'.
"It doesn't matter that a woman's FSH levels are high. As long as a woman has a menstrual cycle and is ovulating, she has a chance of getting pregnant," Dr Nargund says. "Of course, egg quality declines with a woman's age so you have to be realistic. Consultants need to suggest a timeframe – say of a woman trying for six months to a year with her own eggs. But it is vital that she is given the option."
Dr Nargund, who is campaigning to raise the profile of natural and mild IVF in the UK, hopes that one day these options will be offered to all women as a first-line fertility treatment. "As it is safer for the woman and less disruptive, it makes sense to try before using high-dose conventional fertility drugs," she says. "That being said, it is a technique where you usually need more than one treatment cycle to get results."
Sant desperately wants more women to know that natural-cycle IVF is an option for women like her. "It is worrying that I only found out about natural-cycle IVF by chance," she says.
"The other clinics weren't offering it and one clinic told me to forget about having my own children. That is a strong message and it is wrong. The fact is, I had a glimmer of hope and now have a beautiful daughter and a son on the way."
Conventional versus natural IVF – the key differences
* Conventional IVF uses drugs to induce an artificial menopause, followed by high doses of ovarian stimulation. The aim is to produce more than eight eggs to be fertilised in the laboratory. If several embryos develop, two can be introduced to the womb at once.
* Natural-cycle IVF uses scanning techniques to monitor a woman's natural cycle so her egg can be collected just before ovulation. The egg is fertilised in the laboratory in the usual way. If an embryo develops, it is introduced to the womb a few days later.
* If the first attempt does not succeed, it takes a woman's body two to three months to recover from a round of conventional IVF and for a second attempt to begin.
* If a round of natural IVF fails, a woman can try again the following month.
* Conventional IVF can cost from £5,500 to £7,500 per cycle, compared to around £1,500 to £2,000 for natural-cycle IVF.
* The success rate "per cycle" for natural-cycle IVF is around half that of conventional IVF in young women. As this method is less disruptive to a woman's body, she can fit two or three more rounds of IVF into the same time. This means in a year her chances of achieving a successful pregnancy with mild IVF versus standard IVF are pretty similar.
* In older women with high levels of FSH, the success rate of natural-cycle IVF is equal to or greater than conventional IVF. This is because it favours egg quality and implantation of the embryo in the womb lining.