The '4 Minutes' singer said the adoption was an incredibly painful process because it involved so much bureaucracy.

Speaking at the Cannes Film Festival, in France, Madonna said: "It was painful and a big struggle and I didn't understand it. In the end, I rationalised that when a woman goes through natural childbirth, she suffers an enormous amount. I went through my own kind of birthing pains."

However, the 49-year-old singer is not bitter about the experience, and insists it has made her stronger.

She said: "Everything that happens to me is a karmic thing. It was meant to happen."

Madonna also hit out at critics who claim David's mother did not die of AIDS and his father did not agree to the adoption.

She said: "Yes, his mother did die of AIDS and yes, I met his father and he absolutely agreed to the adoption. There is nothing controversial about the adoption."

Madonna was speaking to promote her new documentary 'I Am Because We Are'which premiered at the festival this week.

The film is about the effect of Aids on orphans in Malawi, and features David.