London, July 11 (IANS) Women of South Asian origin are contributing most to Britain’s population boom, says a new study which shows that women in general are now having more children than at any point of time since the 1970s. The Office of National Statistics (ONS) has predicted the British population could reach 71 million by 2031, with migrants and their Britain-born children accounting for 69 percent of the growth.

Eastern European women, particularly Poles, having more children in Britain is only part of the reason. The major contributors are women from South Asia.

Each woman now has 1.91 children on average - the highest since 1973, according to the latest study conducted by the ONS. As a result, the number of births - 690,000 - increased by 20,000 in 2007 compared to the previous year, when there were 1.86 children per woman.

A third of those were born to British mothers and the rest to women originally from overseas. On average, foreign women have 2.5 children each, rising to almost five for those from Pakistan and 3.9 from Bangladesh.

The number of babies born to British mothers is also increasing, but lags far behind immigrants at an average of 1.7 children each.

The study, quoted by The Telegraph, says one factor in the rise is the tendency for foreign-born mothers, particularly from the Indian sub-continent, to have large families. Another is women choosing to have children when they are in their more fertile 20s, rather than delaying until they are in their 30s and 40s.

Those who do delay are having more children due to improvements in fertility treatment. The figures, which relate to England and Wales, indicate the overall fertility rate has now increased for six successive years.