India is the most likely place for the seventh billionth child to be born

The Madanpur Khadr colony is a tenement slum on the southern outskirts of Delhi, the Indian capital. A decade ago there was nothing here but green fields, buffaloes wallowing, goats grazing and the odd small dwelling. Now an estimated 40,000 people live in ramshackle, five-storey, brick and concrete homes, 10 to a room, without sewers or a clean water supply – and often without jobs. No one knows exactly who will be the seventh billionth person on Earth, to be born on the last day of this month, according to United Nations statisticians. But the chances are he or she will be born in northern India – perhaps even in Madanpur Khadr. Here, narrow, rubbish-strewn lanes are filled with young children and scores of heavily pregnant women. India is home to nearly a fifth of the world's population and around 2020 it is projected to overtake China as the most populous nation on Earth. One Indian state – Uttar Pradesh in the north – now has a population of around 200 million people, only a little less than that of Britain, France and Germany combined. Madanpur Khadr lies astride the administrative boundary between Uttar Pradesh and Delhi itself. Chanchal, 27, is one resident. She lives with her husband, a mason, and their three young children in a single 15ft by 10ft ground floor room which they rent for 2,000 rupees (£27) a month. Chanchal, who came from her village in Rajasthan to marry eight years ago, is heavily pregnant with her fourth child, due in the first week of November. Most families in Madanpur Khadr have between four and eight children despite the efforts of Manju Upadhayay, manager of a local NGO, to introduce the concept of family planning. "We do our best but there is some resistance," she said. The colonyMadanpur Khadr was created in 2001 to house slum residents ejected from land in central Delhi by local authorities to make room for middle-class housing and retail developments. A total of 20,000 people were resettled. The population of the neighbourhood has doubled in the decade since then. These are fast growth rates even by Indian standards. The latest national census, conducted this spring, found that India increased by 181 million inhabitants in the 10 years from 2001 to 2011. The population now stands at 1.21 billion. Though the growth rate has slowed, if there is no radical change in trend the country's population is expected to exceed 1.45 billion by 2035. Indian politicians hope the youthfulness of the population will bring a huge "demographic dividend" for the country by boosting economic productivity. But some fear a demographic disaster. The situation in Madanpur Khadr highlights both the hopes and challenges of an expanding population. Local schools in the slum neighbourhood are understaffed, underequipped and hugely oversubscribed. India suffers from a lack of teachers and educational resources at all levels. Chanchal sends her children, three girls aged four, five and seven, to a private school for 1,000 rupees per month (£13.50), and hopes they will have better prospects. "I want them to be teachers," she told the Guardian. Like most of the adults in the neighbourhood, Chanchal is illiterate. The recent census showed a nine point rise in literacy to 74% for Indians aged seven and older. The prospects for India's younger population largely depends on the ability of the economy, currently growing at around 8% per year, to generate enough jobs for them all. With a weak manufacturing base, however, meeting this demand is by no means inevitable. Another deep and intractable problem in India is infant malnutrition, which affects adult cognitive capacities and the future employability of today's young. Almost a half of children under five in India are malnourished. There is also the continuing preference for boys over girls, which has led to widespread female infanticide. The 2011 census showed 914 girls being born or surviving for every 1,000 boys under the age of six, compared with 927 for every 1,000 in the previous census of 2001. "This is a matter of grave concern," said C Chandramouli, the census commissioner at the time of the data's release. Campaigners fear the skewed gender population will lead to social problems when the present generation want to start a family.Finally, there is the sheer pressure of so many people living on such scant resources. This is evident everywhere in this giant country. Wildlife – ranging from birds to freshwater crocodiles, tigers to rare species of monkey – has suffered from loss of habitat and from pollution. The country's creaking infrastructure is overwhelmed with trains and roads already packed with people. Healthcare is rudimentary at best. Women like Chanchal have to travel to the centre of Delhi – a two-hour bus journey — to reach a maternity ward. The roads from the colony are so bad that many suffer premature labour as they are bounced in rickshaws across potholes on the way. Upadhyay, who has watched the neighbourhood double in size, is afraid of further expansion. "When you take a bus from here into the city there are already 15 people crammed into five seats and the road is blocked by traffic. What is going to happen if there are more people?" she said. Chanchal, however, is optimistic. "I have a good life ... my children will too."