The rising number of births could also make the United Kingdom more powerful longer term by boosting the workforce.
"With an increasing population and economy, the U.K. could actually become the largest economy in Western Europe in the next 20 years," said Rossi, noting that other European countries tend to have much lower birth rates than the U.K.
$380 million royal baby boost
Germany is Europe's leading economy and has the biggest population, but statistics show it has a lower fertility rate than the U.K.
Carl Astorri, economic adviser to Ernst & Young, said rising birth rates should help the U.K. deal with the challenges of supporting an increasing number of over-65s in the population as life expectancy increases.