According to preliminary data reported Wednesday by the National Center for Health Statistics more babies were born in the United States in 2007 than any other year in the country's history.

The 4,317,199 births of 2007 toppled the previous record which was held by 1957 which was the height of the baby boom. This new record brings good news and bad news as on one hand it indicates that the US population is more than replacing itself yet on the bad side teenage birth rate showed an increase for a second year in a row.

The increase was slightly higher in women of all ages, including those in their 30s and 40s, while a record share of births to unmarried women was seen at an all time high of 40%. This continued a trend that had been witnessed starting some years ago and more than three quarters of these were in women who were 20 or older.

Duke University's S. Philip Morgan, a leading fertility researcher said for a number of reasons it seemed it was more acceptable for women to have children without husbands.

Stephanie J. Ventura, chief of reproductive statistics at the center and an author of the new report said that despite the increase in the birth rate today the average woman has 2.1 children which is the "magic number" required for a population to replace itself and lower than the earlier average of women bearing three to four children.

The racial and ethnic break up was as follows: 28 % of white babies were born to unmarried mothers in 2007, compared with 51 % of Hispanic babies and 72 % of black babies. The shares of births to unwed mothers among whites and Hispanics have climbed faster than the share among blacks, but from lower starting points Ventura said.

The trend that health officials found worrying was that of the increase in teenagers becoming moms which for a second year showed a slight increase after declining by one third from 1991 to 2005. The rise was of 2 % in 2006 and 1 % in 2007.

"The 14 years with teenage birth rates going down was one of the great success stories in public health, and it's possible that it's coming to an end," said Sarah S. Brown, chief executive of the National Campaign to Prevent Teen and Unplanned Pregnancy, a private group in Washington.

Caesarean section deliveries also registered a high at 32 % in 2007, up 2 % from 2006 climbing steadily, from 21 % in 1996.

Although the number of births in the U. S. reached nearly 4.3 million in 2006, some experts think birth rates are already declining because of the economic recession that began in late 2007.

"I expect they'll go back down. The lowest birth rates recorded in the United States occurred during the Great Depression - and that was before modern contraception," said Dr. Carol Hogue, an Emory University professor of maternal and child health.