A Nigerian family planning expert has told the BBC it would be difficult to implement the suggestion that Nigerians should only have three children. Isaac Ogo pointed to the tradition of polygamy and the belief that the children were seen as a "gift from God" in a male-dominated society. Recent UN figures suggest Nigeria's population could jump to 730 million by 2100 - behind only India and China. UN special adviser Jeffrey Sachs said this prospect alarmed him. "It is not healthy. Nigeria should work towards attaining a maximum of three children per family," he told the AFP news agency. Mr Ogo, from the Planned Parenthood Federation of Nigeria, agrees with the goal but says it will be hard to change the views of many Nigerians. He says Nigeria is a "high birth, high death" society where many people think: "I need to have as much children as I want, as I don't know which will survive." Nigeria is one of the world's worst places to have a baby, according to the UN. About 145 women die each day in pregnancy or childbirth, as do 2,300 children below five years of age. 'Not their business' Mr Ogo also told the BBC's Focus on Africa programme that many women are unable to visit an organisation such as his without their husband's agreement. On the streets of the northern city of Kaduna, some people told the BBC that God decided how many children they had and so it would be wrong to try to limit the number of births. "[The UN] should try to advise the government how to make the lives of Nigerians better, not telling Nigerians not to have children - that is not their business," one angry woman said. But one woman agreed with Mr Sachs, saying that in a poor country such as Nigeria, it was better to have fewer children and look after them properly. Nigeria's population is currently 160m - by far the most populous in Africa but a long way behind those of China and India. As those countries grow richer, the UN predicts their populations will stop expanding, while those in Africa such as Nigeria, will continue to grow rapidly. Source: BBC