40% of US Births were out-of-wedlock in 2007
The stats:

The birth rate rose slightly for women of all ages, and births to unwed mothers reached an all-time high of about 40 percent, continuing a trend begun years ago. More than three-quarters of these women were 20 or older.

... Meanwhile, U.S. abortions have been dropping to their lowest levels in decades, according to other reports. Some have attributed the abortion decline to better use of contraceptives, but other experts have wondered if the rise in births might indicate a failure in proper use of contraceptives. Some earlier studies have shown declining availability of abortions.

... Cesarean section deliveries continue to rise, now accounting for almost a third of all births. Health officials say that rate is much higher than is medically necessary.

"It's the tiniest of baby booms," said Morgan in agreement. "This is not an earthquake; it's a slight tremor."