HANOI, Vietnam (AP) — Nearly half of all births in China are delivered by caesarean section, the world's highest rate, according to a survey by the World Health Organization — a shift toward modernisation that isn't necessarily a good thing.

The boom in unnecessary surgeries is jeopardising women's health, the UN health agency warned in the report published online in the medical journal The Lancet. Unnecessary C-sections are costlier than natural births and raise the risk of complications for the mother, said the report surveying nine Asian nations. It noted C-sections have reached "epidemic proportions" in many countries worldwide.

The most dramatic findings were in China, where 46 percent of births reviewed were C-sections — a quarter of them not medically necessary, the report said. "So many pregnant women ask for a caesarean birth in China, but we always suggest that they have a natural birth," said Dr. He Yuanhua, at Capital Antai Obstetrics and Gynaecology Hospital in Beijing, who did not participate in the study.

"It's bad to have so many caesarean births because natural birth is the ideal way."

The WHO, which reviewed nearly 110,000 births across Asia in 2007-2008, found 27 percent were done under the knife, partially motivated by hospitals eager to make more money.

That mirrors similar results reported by WHO in 2005 from Latin America, where 35 percent of pregnant women surveyed were delivering by C-section.

In the US, where C-sections are at an all-time high of 31 percent, the surgery is often performed on older expectant mothers, during multiple births or simply because patients request it or doctors fear malpractice lawsuits. A government panel warned against elective C-sections in 2006.

"The relative safety of the operation leads people to think it's as safe as vaginal birth," said Dr. A. Metin Gulmezoglu, who coauthored the Asia report. "That's unlikely to be the case."

Women undergoing C-sections that are not medically necessary are more likely to die or be admitted into intensive care units, require blood transfusions or encounter complications that lead to hysterectomies, the WHO study found.

US studies have shown babies born by caesarean have a greater chance for respiratory problems. The Asia survey found the procedure benefits babies during breech births. Reasons for elective C-sections vary globally, but increasing rates in many developing countries coincide with a rise in patients' wealth and improved medical facilities.

In Asia, some women opt for the surgery to choose their delivery day after consulting fortune tellers for "lucky" birthdays or times.

Others fear painful natural births or worry their vaginas may be stretched or damaged by a normal delivery. Some women also prefer the operation because they mistakenly believe it is less risky.

"I think it's safer for the mother and child to have C-sections, and the relatives feel more secure because it's very simple and very common now," said a Vietnamese woman, Trang Thanh Van, 25, just days away from giving birth to her first child. "People worry that using tools to pull the baby out (in a vaginal birth) may affect their brains."

The Asian survey examined deliveries in 122 randomly selected public and private hospitals in 2007 and 2008 across Cambodia, China, India, Japan, Nepal, the Philippines, Sri Lanka, Thailand and Vietnam.

The hospitals were located in capital cities and two other regions or provinces within each country, all logging more than 1,000 births a year.

China's 46 percent C-section rate was followed by Vietnam and Thailand with 36 percent and 34 percent, respectively. The lowest rates were in Cambodia, with 15 percent, and India, with 18 percent.

The study did not discuss specific reasons for the high number of C-sections, but it noted that more than 60 percent of the hospitals studied were motivated by financial incentives to perform surgeries.

At Vietnam's National Hospital of Gynaecology and Obstetrics in Hanoi, about 40 percent of the 20,000 babies delivered there annually are by C-section, said Dr. Le Anh Tuan, the hospital's vice director, who did not participate in the study.

As the capital's largest maternity hospital, it receives the most complicated cases, with many women undergoing emergency surgery. But he said another reason is women with small frames whose babies are simply too large for them to deliver naturally.