More than one in five children born in the UK in 2007 has a foreign-born mother, according to an Office for National Statistics (ONS) report.
Of those, the highest proportions are in the London boroughs of Newham (74.8%) and Brent (72%).
Says the report: "Foreign-born women, who generally have higher fertility, are making up an increasing share of the population, which is also acting to push the overall total fertility rate upwards."
But it notes that since 2004 it has been rising fertility rates among UK-born women that is the largest single factor increasing the overall number of births.
Overall, between 2001 and 2007 the number of births to foreign-born mothers rose by 65%, well above the 6.4% rise recorded among British-born women.
The figures show that the number of births increased each year between 2001 and 2007, mirroring the 14% increase in the proportion of foreign-born women in the childbearing population.
But the report states: "The rise in the overall total fertility rate is mainly due to increasing fertility among UK-born women, since fertility among foreign-born women has remained relatively stable since 2004."
"Yes I think it will. The government should take the opportunity now, however insensitive and divisive to debate fully the unsustainability rather than political point scoring and vague assurances made on the security of the health service in its hands. More injection of money without monitoring does not necessarily bring improvements to health and welbeing" - V Henry, London