When parents tell a child that he or she was conceived from a donated egg, or donated sperm, it can come as quite a shock.
After Elaine Chong wrote about donating her eggs to help other couples have a child, two readers got in touch to explain how the revelation that they were donor children affected them - one said it split his family, the other said it drew hers even closer together.
'My entire existence is a lie'
I found out I was donor-conceived when I was 22. The conversation was not planned. When my younger sister discovered she was pregnant she asked my parents if there were any hereditary family conditions that she needed to be mindful about. Then my parents told her that they couldn't answer her question that she had been born as a result of gamete donation.
My social father (this is what we call the parents who raise us) then told me that was also the case for me. He said they had gone to a doctor at Harley Street who had helped them conceive both myself and my sister, who is three years younger. But that was all he was willing to talk about and neither he nor my social mother wanted to discuss the subject any more.
As I was conceived in the early 80s it's impossible to find records as to who the egg and sperm donors, my biological parents, are. It was rare for that information to be kept on file then.
I'd often wondered why I looked so different to the people that raised me. I'm tall, hairy, with dark eyes and features. My parents are shorter, pale with light eyes. I started wondering if maybe I could be of a different ethnicity. Suddenly my whole existence felt like a lie.
My relationship with my social parents deteriorated and I spent years moving around, doing a number of odd jobs. I also battled with gambling issues. I felt like a gypsy. I should add that my sister had a different reaction to me. She maintains a good relationship with our social parents, whereas mine has almost entirely broken down.
Even though I am now married, with a young child of my own, I am still against gamete donation. We shouldn't be playing around with science like this. If I had been adopted, it would be easier to trace the story of how I came to be and easier to find roots. As it stands it's unlikely that my egg or sperm donor parents knew each other, and I don't know the motivations of why they chose to donate.
I feel that donor conception is a trade in human beings and very few people consider the effects it has on a child.
John, 35, UK
'I also want to be an egg donor'
My sister and I have always been almost opposites - which was the main reason why I could tell something was different between us. She was slim, smart, and a rule-abider. I was more of a wild child with an athletic build. Throughout our childhood, it was always a joking topic, but it was never addressed until I was 11.
My dad and I were in the car and I had brought up again how my sister and I were so different. He said: "Yeah, we can talk about it when we get home." I was like, what? After all this time, now there's an explanation! In a way it was satisfying to know that my premonitions were correct.
At home, it was a full family conversation. My mom cried when she confirmed my suspicions that my sister and I weren't fully related.
She'd had a problem with her IUD implant in the 70s that affected her uterus and the transport of her own eggs. She had never told anyone in her family except for her mother because of the stigma against not being able to get pregnant.
My parents told me that my sister was an in-vitro fertilisation (IVF) baby, with my mom's egg and my dad's sperm, and that I was conceived from an egg donor with my dad's sperm.
It was very emotional. I can vividly remember that.
It's such a fragile state to be in, to have your own kid question where they're from. It was one of those things where my mom thought if I knew that I wasn't necessarily related to her, I would push her away - that's what she conveyed to me.
After, I remember sitting in my room and I felt like I had known it was true the whole time. I had grown up with these differences and my parents never loved me any less. I've never felt betrayed - I've just felt grateful for the chance to be given life.
My mom and I have gotten closer because of it. I think it is the bravest thing she has ever done. I began to see how it had shaped her as a mother too - every night she would tell my sister and me: "We did everything to have you, we're so grateful for you in our lives." Now I understand that they really did do everything.
As I got older, I became more intrigued by IVF. I thought it was very interesting to see how my parents had taken this very new technology and applied it to their lives.
I want to be an egg donor once I finish college because it would make me feel so proud.
I want to represent a successful story of in-vitro. My mom is very supportive of me becoming an egg donor. I think it would make her feel like she has continued the process of family completion in a way.
Donor conception is still seen as a very secretive process, but I think if it were to have more light brought to it, things might change. If I could help at all to de-stigmatise the idea, I would feel very proud.
Elizabeth, 21, US
When to tell the children
If children have been conceived from a donated egg or sperm it's good to tell them early, says Nina Barnsley, director of the Donor Conception Network. Ideally at the age of five, and no later than 10.
This allows them to get used to the idea as they grow, and averts the possibly traumatic experience of a sudden revelation later on. "It ends up being just an exciting story of how they came into the world," she says. "Parents should see it as an open door to continuing the conversation as the child wishes and ages."
If parents wait until their child is an adult, they may be asked why they hid the truth for so long. But late is better than never, Barnsley says, and better than a deathbed confession. "We've had children in their 30s with parents in their 70s when they have the conversation. It can go very well."