One woman confided that it was due to an airborne fertility drug pumped secretly around the village supermarket. Others suggested it was the herding instinct of young families. But whatever the reason, Cambourne was yesterday revelling in its status as one of the planet's reproductive hotspots.
The Cambridgeshire community of 7,600 souls, which a decade ago was windswept East Anglian farmland, has been revealed by statisticians to enjoy a birth rate that is twice the British average and comfortably ahead of the world's five most densely populated nations.
Such is the fecundity of residents in the new-build village, which was founded in 1999 to provide housing for professionals flocking to hi-tech companies in nearby Cambridge, that it has surpassed India (the world's fastest-growing population), China, Indonesia, Brazil and the USA with a birth rate of 24.1 babies per 1,000 women in 2009.
The figure is far ahead of the United Kingdom average of 12.1 births and means that this corner of rural England, a few miles to the west of Cambridge, is beaten only by the likes of Uganda, Niger and Afghanistan in its ability to populate the planet. The result of the hitherto unrecognised Cambourne baby boom is a procession of buggies being pushed along the high street to a squealing soundtrack of recalcitrant toddlers and a mushrooming of infrastructure and activities to accommodate not so much the pitter-patter but the thunder of tiny feet.
Ali Withers, who runs the Cambourne Carers and Tots group, said: "The growth has been extraordinary. When we started the group four years ago, we had around a dozen carers and we fitted into a small side-room in the community hall. Now we have 55 carers and we had to take the largest room available as well as adding space outside. You do look around and think, wow, there are a lot of pushchairs in this village. Most mums have a couple of kids but there are a fair few with four or five."
The numbers are indeed dramatic. An analysis by the Cambridgeshire County Council Research Group found that while Cambourne produced 115 babies in 2004, the figure from April 2008 to this March is 210. It is expected to continue to rise.
It is a phenomenon with which Sarah Humphreys is all too familiar. Like every other headteacher in the land yesterday, she was busy coping with the demands of the first day of the new school year, juggling timetables and distributing uniforms.
But few headteachers will have been going about their work in a school which is so new that it does not have a name and was brought into being after the two other primary schools in the village, originally designed to meet demand for the next 20 years, filled beyond capacity in less than five.
Housed in four Scandinavian-looking portable classrooms, the school opened its doors to 53 five-to-seven-year-olds with a sign that read: "Cambourne Third Primary – Temporary School". It was an indicator that the race to build the facilities necessary to cope with the baby boom has not been without problems. Until this summer, the overflow of pupils who could not get places in Cambourne were bussed 10 miles to a nearby village.
Sitting in her office, which was furnished with a spare table and chairs culled from the dining room, Mrs Humphreys said: "There is no question that there was a third primary needed in Cambourne. The others were full to bursting. There seems to have been a little concern that once opened we might find ourselves with just a handful of pupils. But that has not been the case. There is even the suggestion that the planned expansion of Cambourne means we will need a fourth primary and a secondary school."
All of which begged the question just what is driving the village's reproductive extravaganza?
Residents battling through the gusting wind to do their shopping in Cambourne's scattering of shops offered a wide range of explanations, from boredom-induced babymaking to outlandish conspiracy.
John Hutchings, 34, a father of two, moved to the village in 2002. He said: "For a long time there was a lag between building houses and building other amenities. We're still waiting for the swimming pool. So it doesn't take much imagination to work out what a young couple might do to keep themselves amused on a dark winter's night." Another woman took The Independent aside to suggest that medication to enhance fertility was being added to the air conditioning system of the village branch of Morrisons to increase demand for family homes.
The reality is more prosaic, according to statisticians. Drawn by employment in the so-called crescent of hi-tech industries that stretches between Cambridge and Peterborough, and the more affordable housing that Cambourne offers compared with the two cities, many young couples and families have moved to the village.
Vicky Head, the county council's demography research manager, said: "The high birth rate mainly reflects the fact that Cambourne has a young age structure with a higher proportion of women of child-bearing age than the national average. We can say with confidence that Cambourne has more births than expected for a settlement of its size."
John Vickery, the clerk of Cambourne Parish Council, added: "There must be something in the water. There are a lot of young people. A lot of houses have been bought by couples in their 30s who are ready to settle down."
The Cambridgeshire baby boom is part of a nationwide rise in fertility. The Office for National Statistics revealed last month that the UK population had seen its biggest rise in 50 years to more than 61 million, largely driven by an unexpected increase in the birth rate which saw the arrival of 19,000 extra babies.
In Cambourne, the news that that the village's reproductive spurt had pushed even London and Birmingham, where the birth rate is about 15 per 1,000, into the league of baby-making also-rans was greeted with some pride.
Pushing her twins along the high street, Marie Watkins, 32, a mother of three, said: "It's great. It brings a vibrancy to the village to have so many children around. And at least it proves we're good at something."
Fertile Britain: Baby booming boroughs
Highest birth rates in London (babies born per 1,000 people):
1. Newham 23.90
2. Barking/Dagenham 21.43
3. Hackney 21.14
4. Waltham Forest 20.53
5. Greenwich 19.56
6. Tower Hamlets 19.18
7. Haringey 18.96
8. Hounslow 18.91
9. Lewisham 18.62
10. Wandsworth 18.47
Highest birth rates outside London:
1. Bradford 17.10
2. Birmingham 17.02
3. Watford 16.72
4. Manchester 16.69
5. Sandwell 16.54
6. Harlow 16.08
7. Northampton 16.07
8. Corby 15.77
9. St Albans 15.44
10. St Helens 15.31