Almost 39 percent of the 82,700 infants born in the country in 2013 had non-Swiss mothers, the federal statistics office (FSO) said in a report issued on Tuesday.
That compares with a rate of 19.6 percent in 1990, the office said.
The numbers were released a day after statistics showing continued high immigration to Switzerland in the past year.
The country’s population increased by 100,600 to 8.14 million, with net immigration of foreigners amounting to 89,500.
The number of foreign women surpassed 900,000 in 2013 to account for 22.1 percent of the female population, up from 14.4 percent in 1990.
A higher proportion of non-Swiss women are also of child-bearing age than among Swiss women, the FSO said.
The rate of fecundity among foreign women aged between 15 and 24 is four times higher than among their Swiss counterparts, who are less likely to become pregnant.
Three-quarters of foreign women giving birth last year were Europeans, accounting for 29.2 percent of the overall total.
A quarter of these came from the former Yugoslavia (Kosovo, Macedonia, Serbia, Bosnia-Herzegovina, Croatia, Montenegro and Slovenia).
A further 18.9 percent came from Germany, followed by Portugal (13 percent), Italy (8.7 percent), France (6.8 percent), Turkey (4.7 percent) and Spain (3.3 percent).