Sarah's* three-year-old is a perfect little boy, right down to his curious webbed toes.

"That's a family trait we never expected. It was definitely not in the donor's profile - and neither were the tantrums," says the 37-year-old, with a laugh.

Her twins, a boy and a girl, were conceived using genetic donors. "After five unsuccessful cycles of IVF, the doctors said my eggs were of such poor quality that the treatment was never going to work. It was heartbreaking."

The fertility specialists suggested egg donation.

Dr Paul le Roux, president of the Southern African Society of Reproductive Medicine and Gynaecological Endoscopy, says South Africa's first birth by egg donation happened in 1986. The numbers and success rates have climbed steeply since about 2000, as technology improved.

"I would estimate that out of the 6000 conceptions by IVF treatment per year, 1000 babies are conceived by egg donation," says Le Roux.

And the demand has grown, because more couples are now deciding to have children later in life, when their genetic material is past its prime.

While the success rate for IVF using a woman's own eggs is about 20% to 45%, depending on her age, conception by egg donation has a 65% chance of success.

Sarah says they had three further unsuccessful tries with donor eggs. "My husband found out he had fertility issues too, so we also went with a sperm donor.

"And yes, we still feel our kids are our own. We just borrowed the genetic material from people who were willing to share it with us.

"It was a difficult decision. Not being able to visualise the person who is donating is daunting. Physical attributes were important - I wanted the kids to look like us. But choosing your child based on a piece of paper provided by someone who may or may not be honest is something else."

Egg donors are anonymous, but provide childhood photographs and a detailed profile of themselves. Sperm donors share three lines at most: race, age and physical attributes.

"We chose donors with dark hair and eyes but ended up with blonde kids anyway," she says.

The egg donor goes through a rigorous process of fertility treatment and retrieval after she is selected. The fusion is done in a lab and the embryos develop for a few days before they are implanted in the recipient mother. "Then you pray. It is an agonising two-week wait before you hear whether the embryo embedded successfully."

Although the couple cannot contact the donor personally, she can be informed of the success or failure of the procedure and the birth of the child or children - multiples are common with donor-conceptions.

"I got a touching e-mail from her via the agency, I know her birthday and on Mother's Day she is in my thoughts. I am curious. I would love to see what she looks like, but legally I can't."

The couple did not consider adoption. "I wanted to carry our children," says Sarah. "I had to see a psychologist, who helped me mourn the loss that I felt every time I had a failed pregnancy - and to help me realise there are other means of being a mother.

"Going through all that, pregnancy and delivery, makes a person a mother, not genetics.

"But I also had to work around the fact that my kids might reject me as their mother when we eventually tell them their conception story."

They have started explaining the concept of a biological mother versus birth mother through story books. A popular one is about a duck with broken eggs who is given a present of new eggs by another kind duck.

"We have only told my parents and siblings, maybe two friends. I want the kids to hear it from us, bit by bit, so it doesn't become a nasty surprise one day. They must not feel like they were lied to all their lives."

She is slightly nervous about that day, but says they are happy with their decision.

"We went through so much disappointment and loss. Suddenly someone puts a hand out to help you, with a nearly 70% chance of it working, which is a massive success rate for fertility patients. After eight years of trying, my only regret is that I waited so long to go the donor route. It makes me appreciate our kids so much more."

Clinical psychologist Mandy Rodrigues specialises in fertility medicine. She says the majority of her patients choose not to tell their children that they were conceived with a donor egg.

"It is simply because they cannot trace the donor, so that knowledge will not empower the child, there is nothing to be gained. It is a little white lie to protect the child. But they then choose to not tell anyone else about it either and really just forget about it.

"On the other hand, some people may find they are so comfortable about their fertility choice that they tell everyone about it and allow their child to tell whomever they want to, also.

"If they decide to tell, they explain it as something extremely special, a gift. Unlike adoption, it is not about being abandoned by someone, so it is not an issue of rejection."

For those children, she says, it could potentially come up when the child reaches adolescence. "Teenagers will always throw something in your face, and this will probably be it. So we give the parents the skills to manage it when it happens."

She says it can take years for parents to decide on egg donation. "By then, it is normalised for the recipients or they figure it is not for them. If you are comfortable as a parent, your child will be fine."

SPERM donors get a few hundred rand for their donation, while egg donors receive R6000.

"For the male donor, it is really ejaculation in a cup and it is over," says Lindsay Broome, who works with egg donor agency Nurture.

"At sperm banks, a recipient will get a spreadsheet of characteristics to choose from, but not much detail." Often students, sperm donors fill in a few lines about their race, hair and eye colour, make a deposit and leave.

On the other hand, an egg donor is altruistic, says Broome. "Sure, some people do it for the money. But the procedure is really not worth it. It entails invasive tests, fertility drugs, an in-hospital retrieval procedure and recovery. It is physically taxing in a way that the money doesn't match up."

And not everyone can donate.

"It may sound shallow, but impoverished people won't likely make it onto a donor list, so it is not a way of earning a living. People choose donors who are educated, firstly." Some agencies ask for school reports.

"Logistically, they must have an e-mail address and internet access, because there are many doctors' appointments and procedures to schedule and reminders to take their fertility injections. Recipients will also choose a person who has a good family history. They also have to be a healthy weight, aged 20 to 34, and drug-free."

She can contribute to six successful births.

"Then there are donors who might tick all the boxes, but are never chosen on physical characteristics," says Broome.

Candace Whitehead was a student in her 20s when she found Nurture.

After the psychological and medical-screening, donors are placed on a course of medication that stimulates follicle growth.

"I know that the daily injections put off a lot of women and honestly, they were probably the worst part," says Whitehead. "You have further scans with the doctor before being given two shots to ripen the eggs, 36 and 24 hours before you donate."

The process takes about 14 days.

The 20-minute, non-surgical donation procedure was mildly painful. Under anaesthetic, a needle is inserted into the ovary via the vagina to retrieve the eggs.

She does think about meeting the recipient's children. "I'd like to see that they're healthy and obviously I'm curious about how much they resemble me. But that's about it.

"A friend of mine was shocked that I wouldn't want to be involved in 'my' children's lives. But they aren't my children. They never were."

Amina,* a bubbly mother of three, from Nigeria, says she decided to donate her eggs after a Facebook ad for egg donors jogged a memory.

"I had an aunt who had fertility issues. In my culture, being Yoruba, you are expected to have a child in the first year of marriage, or even before a man contemplates marrying you. A woman who is unable to have a child is discarded by her husband and society.

"My aunt told me she had to travel abroad to fall pregnant because a lady was going to donate her eggs. It was shocking, difficult to accept. But I have three cousins now, which is a blessing."

The 29-year-old, who runs a catering outfit with her husband, says she is "hyper-fertile". "We conceived really easily, so I thought, why waste the gift I have? I have my own children and, while I am able, I might as well give to those who don't have. Otherwise, it is wasted DNA."

She went through the donation process twice.

"Look, the money is nothing, considering what you have to do. I chose to do it. The idea was quite scary; doctors, needles, hormonal changes. But from the first retrieval they got 16 eggs, 22 the second time."

Amina says the numerous doctors' visits can be taxing. "You can opt out at any time. But every time I went in, I saw these photos of beautiful babies on the wall and I was encouraged to carry on.

"The first implantation didn't work - I was very disappointed. But I am told the lady flew in from America for the procedure. That is sad. Imagine her sacrifice! The second time around, when I found out someone was pregnant, it was wonderful."

She will donate again. "Some things we have no control over, like fertility. But especially for recipients, let it be said that you tried."

IT is cosy in Dawn Blank's offices: white with a tinge of pink, warm lighting and soft carpets. It's fittingly womb-like for the place where couples come to choose their child's genetics. Her agency, Gift Ov Life, pairs egg donors with prospective parents.

"It is easy to choose a profile off the website, but we always meet with the couple to talk them through the process, explain the options and work out the long-term questions," she says.

"There is a recent study in epigenetics, which found that the carrier contributes 50% of the genetic profile of the baby. We didn't realise that before, but it comes from the hormones, shared blood etc in utero.

"The study was conducted with surrogacy in mind, but it is obviously a positive for those who go the egg-donation route. Usually the partner's sperm is used, so it is a genetic addition from the father."

The prospective parents consider donors who match their own physical characteristics as closely as possible. "But I have a 50-year-old Indian client who chose a white donor, it didn't matter to her," she says.

Not every couple can make the choice. Donor-conception is expensive. With medical costs around R65000, donor fees and the agency's finding fee, it could add up to about R90000.

"The costs mean there are far more donors than recipients at the moment. We have about 70 donors around the country, but it is not affordable for many couples. Medical aid does not cover egg donation. Some say they will save up for five years and come back."

They do fertilisation tourism for overseas clients.

"About a third of our couples come from Australia, a few from Britain and Europe. They have the implantation procedure, then go on holiday to the Kruger while they relax and wait for the process to happen," says Blank.

"We use young donors. The younger the DNA is, the easier it is to replicate all the way to full-term. The reality for middle-aged women is that DNA that is 40 years old will battle to replicate itself. Half of those pregnancies result in miscarriage, if there is conception at all," says Blank.

Couples also appreciate the anonymity of the process.

"In other countries, the donor is not always anonymous, so at 18, the child can choose to find their donor. As a result, there aren't many donors. Here, not even the gynaecologist needs to know that a couple has used a donor egg."

Blank says that once couples understand the science, they consider the opportunity a blessing.

"People save lives donating blood and bone marrow. When a woman donates her eggs, she is giving someone an opportunity to create a life."

*Not their real names