On British Boston's baby boom

The Guardian's Sarah Boseley and Emine Saner have produced an interesting if somewhat impressionistic new article on Britain's recent growth in fertility ("The new baby boom"), starting with Boston, namesake of the American Boston's, one of the more notable communities namesake located in Lincolnshire, and a community with a TFR of 2.8.

In the shortlived bursts of sunshine, Boston is prettier than its grim reputation suggests, but it still has obvious pockets of deprivation, with some shops boarded up. Asked for directions, a woman in a cafe says "go down there, between the jobcentre and the rundown Kwik Save", which tells you quite a bit about certain areas of the town. It has one of the highest levels of immigration in the UK – it is estimated that a quarter of the population are new arrivals, migrant workers mainly from Portugal and eastern Europe who have come to work in factories around the town packing fruit and vegetables.

Sandra Silva, 34, who moved to the town from Portugal six years ago and works in a factory, is due to give birth to her second child any day now. "There are loads of babies here," she says. "Four of my friends are pregnant." She says she doesn't know why so many babies are being born. "Maybe it's because there's not a lot to do."

But one English mother in her 40s has another view. "It's the foreign workers, isn't it," she says, "but you're not supposed to say that." (This is why she won't give her name.) It is an incendiary topic in this town. Asked if it is because of an increase in migrant workers, Elizabeth Grooby, matron for maternity at the local Pilgrim hospital, is careful with her answer. "We did have some increase but it appears to be reducing, and it is certainly not the only factor." Last year, the maternity unit delivered 2,178 babies, about a 10% rise, and they have taken on new staff to cope. "This year we haven't seen the same sort of increase, it's stayed the same," she says.

Some locals believe that Boston's high fertility relates to a long history of sustained high fertility in rural areas. The postponement of fertility seems to be key, however, and demographer David Coleman connects it to a long history of postponed fertility as birth control in England coupled from the mmid-20th century on with effective birth control and women's emancipation.

Reading the tabloid shock headlines, you would have thought the only people having babies in Britain were hapless teenage mums, while desperate fortysomethings who have left it too late queue at the IVF clinics. In fact, it's not like that. Over the past five years, the highest fertility rates have been among women aged 30 to 34 – probably women with careers who take a conscious decision to have a baby just before their fertility begins to decline, as it does rapidly after the age of 35.

David Coleman, professor of demography at Oxford University, says one of the main factors across the UK in the complicated dance of procreation and population has been women's choice to delay childbirth. "It has been happening everywhere since the end of the baby boom in the very early 1970s," he said .

The thriving fertility clinics are a result of the trend, but not the cause of the baby boom. About 12,600 babies were born as a result of IVF in 2006, the last year for which there are complete figures. Even allowing for a rise similar in scale to that over the previous couple of years, no more than about 14,000 IVF babies would have been born in 2008 – a fraction of the nearly 800,000 total.

Most of these mothers arrive at the clinics because they have left it too long to conceive easily. "Over the last 10 years, the age profile has increased quite markedly," said Dr Allan Pacey, secretary of the British Fertility Society. But he doesn't see any likelihood of IVF contributing further to the baby boom. "There is not a major year-on-year change now. There is not any evidence to suggest that there is an unmet demand."

According to Coleman, women have been delaying having children since at least the 16th century, which is when parish registers were introduced. From 1550 to 1930, the average age of marriage was 25 for woman and up to 20% of females never married. It was a way of limiting family size. "If you marry late, even though you practise no contraception after marriage, the birth rate is going to be moderate," said Coleman. Nor was there much childbirth outside of marriage – never more than 10% of babies born out of wedlock in Britain and often only 5%.

Coleman suspects that Britain, unlike more family-dominated cultures like Italy, may be able to better support autonomous women, while a recent celebrity culture of births and growing subsidies may promote fertility. Then again, the ongoing recession may do the opposite.