(CNN) No matter where a family lives, welcoming a baby into the world can be a joyous occasion -- yet how a woman experiences birth varies drastically from country to country.

The number of births by cesarean section is on the rise, climbing from about 16 million (12.1% of all births) in 2000 to 29.7 million (21.1% of all births) in 2015, according to a study published Thursday in the journal The Lancet

"We knew that globally, C-section rates were increasing for quite some time now, but that now more than one in five babies are delivered by C-section is striking," said the study's first author, Dr. Ties Boerma, a professor at the University of Manitoba and director of the multi-institutional research initiative Countdown to 2030 for Women's, Children's, and Adolescents' Health.

The research revealed that C-sections remain more common in certain parts of the world.

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In 2015, its use was up to 10 times more frequent in Latin American and Caribbean regions, where it was used in 44.3% of births, than in West and Central African regions, where it was used in only 4.1% of births, according to the study.

In the United States, 32% of births were by C-section in 2015, an increase from 23% in 2000, the data showed, and in the United Kingdom, 26.2% of births were by C-section in 2015, up from 19.7% in 2000.

Cesarean section, or C-section , is a surgical procedure used to deliver a baby in which the child is removed through a surgical opening in the mother's lower abdomen area rather than birthed through the vaginal canal. Procedures can be planned, but many occur when unexpected childbirth problems arise, putting the mother's and/or the infant's life at risk.

The new study noted that C-section should be universally accessible -- as it can be life-saving in some cases -- but a rise in C-section for non-medical emergencies has become of concern because the procedure can pose risks , such as risk of infection or postpartum heavy bleeding.

In a separate move on Thursday, World Health Organization published new guidance on non-clinical interventions specifically designed to reduce unnecessary C-sections. The key recommendations include educational interviews, use of clinical guidelines, requirement for second opinion for C-section, and interventions aimed at health organizations, such as collaborating with midwives.

"It is crucial that women who need caesarean sections are able to access this potentially life-saving procedure, but equally unnecessary procedures should be avoided, so that the lives and well-being of women and their babies are not put at risk," Dr. Ana Pilar Betran, medical officer at WHO Department of Reproductive Health and Research, said in the organization's announcement of the new guidelines.

Where C-section rates are highest and lowest

"C-section is not accessible in many developing countries, and especially not to poor women. Much more needs to be done to ensure that all women have access to C-section," said Boerma, of Countdown to 2030

On the other hand, "the large increases in C-section use to levels well over 30% in many countries, often for non-medical indications, is of concern given the risks for both women and children," he said. "It is important country ministries of health, the medical profession and civil society critically consider these statistics and ensure that overuse is minimized."

The optimal frequency of C-section use in a population remains difficult to determine, but in 1985, the WHO stated that there was "no justification for any region to have a caesarean section rate higher than 10-15%."

In 2015, WHO released a statement indicating that "at population level, caesarean section rates higher than 10% were not associated with reductions in maternal and newborn mortality rates" and that "every effort should be made to provide caesarean sections to women in need, rather than striving to achieve a specific rate."

The new study in The Lancet used data from WHO and the United Nations Children's Fund to describe trends in live births across 169 countries between 2000 and 2015. The researchers stopped at 2015 because only a few countries had data points beyond that year.

Based on the latest data, the researchers found that the country with the lowest C-section rate, at 0.6% in 2010, was South Sudan and the country with the highest, at 58.1% in 2014, was the Dominican Republic.

Other countries where more than half of births were by C-section were Brazil, at 55.5% in 2015; Egypt, at 55.5% in 2014; Turkey, at 53.1% in 2015; and Venezuela, at 52.4% in 2013.

When the data was examined by region, the researchers found that C-section birth rates in 2015 were:

4.1% in West and Central Africa

6.2% in Eastern and Southern Africa

29.6% in the Middle East and North Africa

18.1% in South Asia

28.8% in East Asia and the Pacific

44.3% in Latin America and Caribbean

27.3% in Eastern Europe and Central Asia

32% in North America

26.9% in Western Europe

"The big differences in the use of C-section are a major finding," Boerma said.

In 2015, "15 countries including Brazil, Egypt, Turkey and Mexico have C-section use over 40%, while the average for west and central Africa is only 4%," he said.

"In developing countries, or low- and middle-income countries, wealthy women have more than five times higher C-section use than poor women. Part of this is because poor women more often deliver at home, but even if they reach a health facility, they are almost 2.5 times less likely to get C-section," he said.

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Countries with C-section use of 15% or more were more likely to have higher levels of socioeconomic development, women's education, urbanization and density of physicians and lower fertility rates than countries with C-section use in less than 10% of births, according to the study.

In the US, where 32% of births were by C-section, there were also state-by-state differences.

In 2016, Mississippi had the highest cesarean delivery rate in the US at 38.2%, followed by Louisiana at 37.5%, Florida at 37.4% and New Jersey at 36.2%, according to separate data from the US Centers for Disease Control and Prevention

Utah ranked lowest at 22.3%, followed by Alaska at 23%, Idaho at 23.9% and New Mexico at 24.8%, according to the CDC.

As for the new study, it had some limitations, including that the researchers were unable to obtain more recent data for all countries and that the data relied heavily on self-reported survey responses for births in low-income and middle-income countries. Self-reported data run the risk of bias.

"Cesarean section is correlated with reduced breastfeeding , but then of course the complication rates, the mobility, the mortality," said Zeck, who was not involved in the new study.

"So there are several downsides of cesarean section, but we also have to see it as a lifesaving intervention and as something that is necessary in many cases," he said.

"Certainly, the issue is that in some settings, we have too much, and in many settings -- in African countries, for instance -- we have too low, and the too low is even worse because although we are saying we have too many cesarean section rates, we still have to make sure there's sufficient cesarean section rates in many of those African countries," he said. "I think there's danger in saying to 'decrease, decrease, decrease,' but we forget about those settings where we still don't have enough cesarean sections. Both are very important."

A call for help

A series of separate papers was published alongside the new study.

One examined the short-term and long-term health effects of C-section on a mom and baby, such as how the surgery is associated with a higher risk of complications in subsequent pregnancies for the mom and a higher risk of asthma for the child.

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The other paper examined possible interventions to help reduce the use of unnecessary C-sections. The paper noted that various factors drive the rise in C-section use, including that some women may request C-section due to fears of labor or convenience and that some physicians may use C-section to avoid difficult deliveries or risk of litigation.

Some of the interventions described in the paper include having midwives working more closely with physicians, addressing women's fears of labor pain or concerns with vaginal deliveries, and promoting prenatal care.

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The International Federation of Gynecology and Obstetrics published a position paper alongside the new study calling for governments, UN partners, professional organizations, women's groups and other stakeholders to help reduce unnecessary C-sections.

"Worldwide there is an alarming increase in caesarean section (CS) rates," the paper said. "The medical profession on its own cannot reverse this trend. Joint actions with governmental bodies, the health care insurance industry, and women's groups are urgently needed to stop unnecessary CSs and enable women and families to be confident of receiving the most appropriate obstetric care for their individual circumstances."