March 4, 2010 -- It is something we take for granted in the United States. A woman enters the hospital to give birth and she emerges a couple of days later with a beautiful bundle of joy.

That is how it usually goes. But this story is about the rare exception -- women who die within 42 days of childbirth. In the health care community it's called simply "maternal mortality." And in the U.S., many experts believe it is on the rise.

According to the World Health Organization, the U.S. ranks behind more than 40 other countries when it comes to maternal death rates, with 11 deaths per 100,000 pregnancies when measured in 2005. More women die in the U.S. after giving birth than die in countries including Poland, Croatia, Italy and Canada, to name a few.

Watch "World News with Diane Sawyer" tonight for more of Kate Snow's report on maternal mortality.

A new report out of California found the number of women who died in the state after giving birth has nearly tripled over the past decade, from 5.6 deaths per 100,000 to 16.9 per 100,000 in 2006. The report was commissioned by the California Department of Health but has not yet been publically released. ABC News first learned of its existence from a watchdog group called "California Watch."

Death after childbirth is still rare, but experts say many of those deaths could have been prevented.

"We've been able to double-check the data so we can truly say there is a rise," said Dr. Elliott Main, chairman of the California Maternal Quality Care Collaborative, which worked on the report.

"Most women died from hemorrhage, from deep vein thrombosis or blood clots, and from -- this is the surprise -- from underlying cardiac disease," added Main.

The Joint Commission, the leading accreditation and certification group in the United States for hospitals, issued an alert Jan. 26, 2010 stating that "current trends and evidence suggest that maternal mortality rates may be increasing in the United States."

"As many as half of maternal deaths are preventable," said Dr. Mark Chassin, president of the Joint Commission. "The rate of maternal death today is not acceptable in the United States. We need to work much harder than we have been to reduce it."

Maternal Mortality Rising: One Family's Story

In some cases, the chances of maternal mortality rise simply because important warning signs are missed. Jim Scythes knows first-hand how important those warning signs are and how tragic the consequences of missing them can be.

"I just think it's unbelievable that in our country today people still die of childbirth," said Jim Scythe. "I had no idea that anything like that could've happened when we went to the hospital that Friday morning."

It was March of 2007. Jim's wife Valerie had a scheduled cesarean section that seemed to go well. Their daughter Isabella was born.

But by the next day, Jim started to notice clues that all was not well. He says his wife's legs felt hard to the touch.

"She sat in her bed for 30 hours after her surgery and then got herself up and collapsed," Scythe said.

A blood clot in Valerie's leg had moved to her brain and caused a stroke. She later died.

"I look at Isabella and I think 'you're never gonna know how wonderful your mother was,'"Jim says now. "We all feel robbed."

Doctors Say Obesity & C-Sections May be Increasing Risk

Doctors say it's hard to pinpoint exactly why the numbers are rising. Experts have cited the growing number of obese mothers as a big factor -- 20 percent of all pregnant women in the U.S. are now obese at the start of their pregnancy, according to the Centers for Disease Control. These women are more likely to have underlying health conditions, including diabetes or asthma, which can lead to pregnancy-related complications.

The popularity of scheduled C-sections has also been cited by public health experts as a possible cause for rising maternal mortality rates. The latest data from the CDC shows that 31 percent of the mothers now choose to have C-sections, up 50 percent since 1996. Studies have repeatedly shown a higher rate of mortality in mothers who have a C-section delivery, especially those who have multiple C-sections.

"If the risks of a Cesarean birth are small, they're magnified greatly when you add many more Cesarean births each year," said Main, adding that "not that many women actually choose to have an elective C-section at the beginning, but it's easy to fall into a pattern of care that ends up resulting in a C-section."

Dying from Childbirth: Hospitals Can Do More

"These are all wake-up calls across the country that we need to do things differently," said Dr. Erin Dupree, vice president of patient safety at Mount Sinai Medical Center in New York.

While no one can know for certain in Valerie Scythes' case, simple devices called compression boots could have helped. The boots are worn around the calves and keep blood pumping to hopefully prevent clots.

Mt. Sinai Hospital in New York is at the cutting edge of preventing maternal mortality, trying to turn the trend around in the United States. For women who have a C-section at Mt. Sinai, inflatable boots are standard practice, but providing the extra treatment can be expensive. While the compression boots cost only $14, the machine that inflates them costs $4,600.

Dupree admits that the costs and lack of awareness of the technology might be keeping some hospitals from using compression boots, but a good portion of what Mt. Sinai does costs nothing at all.

Doctors and nurses at Mt. Sinai work constantly at improving communication and training to make sure that staff members ask patients the right questions and that patients are empowered to speak up when something doesn't feel right.

For more on maternal mortality and pregnancy complications, visit the CDC's page on the topic by clicking here.