Nutrition in pregnancy: good nutritional status of the mother promotes the growth of the fetus causing the increase in cases of cesarean delivery
The gradual improvement in maternal nutrition in recent years may be behind the increasing number of women who give birth to their babies by cesarean section. The good nutritional status of mothers seems, in fact, to favor the development of a fetus too large for natural delivery. This theory would explain the huge discrepancy in the frequency of C-sections in different parts of the world, and would also be confirmed by the increasing number of these in developing countries.
These are the findings of a study conducted by a team of researchers at the University of Vienna, and published in Proceedings of the Royal Society B.
Frequency of cesarean delivery: huge differences in different countries of the mworld
Although the WHO (World Health Organization) has suggested an ideal rate for cesarean sections of 10% to 15%, the current frequency of this type of delivery varies among social and demographic groups, ranging from 1% to 2% in many sub-Saharan African countries to about 50% in Egypt, Turkey or Brazil. In developing countries, the incidence is also, increasing rapidly. In Europe, incidence rates range from about 15% in Scandinavia, to more than 35% in Portugal and Romania. In Italy, cases of cesarean delivery have increased greatly over the past twenty years, from 11.2% in 1980 to 33.2% in 2000, with substantial differences between one region and another. Despite differences in the traditions of obstetrical practices, health care system, and feeding styles, the variation in the cesarean rate remains staggering. Some studies have shown a tendency for obese mothers to give birth to very large babies and an increased risk of feto-pelvic disproportion, that is, the phenomenon that occurs when the diameter of the maternal pelvis is narrower than the diameter of the fetal head. According to some studies, women exposed to malnutrition during childhood and early adulthood, with short stature and narrow pelvic canal, who then adopted a high-calorie diet during pregnancy, give birth to large infants running serious risks during labor due to feto-pelvic disproportion. The high-calorie diet also affects the balance between maternal and fetal metabolism and may lead to an increased duration of gestation, with increased risks of post-term delivery and obstetric complications.
Data confirm the relationship between mother's physical state and infant size
The team of researchers related the role of maternal nutrition in differences in cesarean delivery rates, finding that proper nutrition may contribute to the development of a disproportionately large fetus.
"Because the fetus represents a generation ahead of the mother, on average it experiences environmental conditions even better," said study co-author Philipp Mitteröcker, an evolutionary biologist at the University of Vienna.
Paradoxically, then, environmental conditions that have improved so much in recent decades may make natural deliveries more difficult and thus increase cases of cesarean delivery, because on average the fetus is larger than the optimal size for natural delivery.
Scientists have speculated that changes in recent decades may have affected the number of cases of cesarean deliveries in different countries. In fact, the mechanism whereby environmental and nutritional influence on maternal and fetal body size is well documented by numerous scientific researches.
The details of the study
During the research, the Viennese authors began by examining worldwide data regarding national cesarean section rates and changes in the stature of adults born between 1896 and 1996. C-section rates were estimated over the period from 2005 to 2017; women who had given birth during this period were born between the 1970s and 1990s. The frequency of cesarean delivery was calculated as the total number of cesarean deliveries divided by the total number of child births. The results indicated that environmental changes had a strong effect on the average increase in body stature, determined to be about one millimeter per year; and that this may cause an increase in cesareans of about 10 percent. Growth in body size was typical in many countries during the 19th and 20th centuries and still occurs in many emerging countries. The team also collected data on national rates of obesity and diabetes and the average age of the mother at first birth, all of which are known to determine the outcome of the work at the individual level. According to the researchers who conducted the research, this not only explains part of the increase in cesarean cuts in many countries, but sheds new light on historical birth transitions and challenges the World Health Organization's guidance, which has suggested an ideal rate for cesarean cuts between 10 percent and 15 percent.
Socioeconomic development influences the frequency of cesarean deliveries
The results obtained from the study highlight the need for a more differentiated view that takes more account of differences between geographic and social groups. According to the results obtained from the study, socioeconomic development and access to health care affect the frequency of cesarean rate through multiple mechanisms, but the strongest direct effect was found to be the average increase in stature. These results indicate that socioeconomic growth history affects through its action on pre- and postnatal growth, the relationship between maternal and fetal size, and thus the difficulty of labor. The study thus encourages, a paradigm shift away from purely cultural explanations of cesarean delivery rates toward a biological and cultural combination that includes sociocultural transitions, human anatomy and physiology.
Source: Eva Zaffarini and Philipp Mitteroecker "Secular changes in body height predict global rates of caesarean section."; Proceedings of the Royal Society B
