However, 60% of the 169 countries surveyed are above this range, while a quarter of the countries are below, putting the mother and the child at risk, the study that is based on figures from the World Health Organization (WHO) and UNICEF.
"The large increase in caesarean sections, mostly in comfortable and unhealthy environments, is problematic because of the associated risks for mother and child", says study coordinator Marleen Temmermann (Aga Khan University).
C-sections are considered medically necessary when the duration or logistics of vaginal delivery would put the birth parent or baby in danger - say, in the event of fetal infection - according to the Mayo Clinic.
"Although there is nearly universal consensus that c-section use has increased beyond the reasonable level of need in many countries, effective interventions to optimise use have proven elusive", explains Ana Pilar Betran, a key contributor to the series and an expert in public health and obstetrics at the WHO.
In at least 15 countries, more than 40 percent of all babies born are delivered by C-section.
The number of C-section births around the world has almost doubled since 2000, and only a fraction of those surgical procedures are medically necessary, according to a series of three papers published today by an global coalition of researchers from the World Health Organization, Yale University, King's College London and elsewhere.
But the procedure is unavailable to many women in low-income countries and overused in many middle- and high-income countries, the researchers found.
The authors suggest that this could be explained by persistent issues with shortages in health facilities and staff in vulnerable and rural populations.
"In cases where complications do occur, C-sections save lives, and we must increase accessibility in poorer regions, making C-sections universally available, but we should not overuse them", she said.
The researchers also warned that in many settings young physicians are becoming experts in C-section, while losing confidence in their abilities to assist in vaginal birth.
There's a balance to be struck in terms of promoting C-sections in certain areas and curtailing their use in others, the report concludes. The procedure scars the womb, which can lead to bleeding, ectopic pregnancies (where the embryo is stuck in the ovaries), as well as still- and premature future births.
In North America alone, C-section births rose from about 24 percent to 32 percent during that time span, the study found.
"What is left unresolved are the tensions generated when women's agency in choosing a caesarean section go against medical directives to intervene against them", says a Lancet editorial published along with the series. Professor Jane Sandall, one of the study's authors, said in a release. "Joint actions with governmental bodies, the health care insurance industry, and women's groups are urgently needed to stop unnecessary C-sections and enable women and families to be confident of receiving the most appropriate obstetric care for their individual circumstances".
"The medical profession on its own can not reverse this trend". The situation has led gynecologists to question this "epidemic", as reported in a report published Friday in the British scientific journal The Lancet.
They also target healthcare professionals, calling for mandatory second opinions and the introduction of clinical practice-based guidelines for when caesarean births are recommended.
There were not only different C-section rates between countries but also within them according to women's socio-economic status and access to medical facilities.