A research team of the University of Malaga (UMA) in the area of Medicine and Psychology has analyzed the effect of the type of delivery on twins‘ psychological development and intelligence, demonstrating that cesarean section carries an independent risk in these multiple births.
“Twins are very vulnerable, since their birth frequently ends prematurely and they often present pregnancy and labor complications,” says Professor Ernesto González Mesa. Based on this study, he says the possible difficulties that may derive from cesarean section are very common in multiple births.
“We have verified that cesarean section becomes a risk factor to development.
This is why gynecologists firmly believe in vaginal delivery benefits, and we defend the use of this surgical intervention only as an option when problems arise,” says González Mesa.
This study, published in the scientific journal Frontiers in Psychology, involved a total of 160 twins who were born in Hospital Materno-Infantil in Málaga in 2005; there were 7000 births, and almost 300 were multiple births.
From the sample of all twins, 55 percent were born by vaginal delivery and 45 percent by cesarean delivery.
In a first stage of the study, the participating children’s intelligence and neuropsychological and psychopedagogical development were tested.
The results were compared in a second stage with information on obstetric and perinatal variables, such as type of delivery, problems, maternal age or newborn weight, among others.
“When comparing all data, we found that those children with a lower intellectual level and cognitive development were born by cesarean delivery,” explains María José González Valenzuela, professor from the Evolutive Psychology and Education Department and main researcher of the study.
She says that apart from early diagnosis, the study seeks intervention through activities at school and primary health care centers.
In this regard, Counselor Olga Cazorla Granados, co-author of this study, adds that there is an increased tendency in educational environments to search for neurological factors to explain difficulties in psychological development.
Addressing the major reading, writing and calculating difficulties that twins often have, and identifying benefits of vaginal delivery as against cesarean section, for example, the neurological effects that children’s intestinal flora, different in each type of delivery, may give rise to, are other future lines to progress in this study, in which Professor Dolores López Montiel, from the Department of Psychobiology and Behavioral Science Methodology, has also participated.
Cesarean sections can save lives, but rates well above the World Health Organization’s recommended 15% ceiling in most developed countries suggest that many procedures are unnecessary1.
In the OECD, the rate of caesarean section has increased from 14.4% of deliveries in 1990 to 25.8% in 20092, growth that cannot be explained by increases in obstetric risk factors, including those associated with delayed and multiple infant pregnancy and maternal obesity3–6.
Instead, this growth is believed to be related to increased maternal request and changes in clinical practice7.
A concern is that many procedures are made without considering possible long-run implications, such as reduced fertility8. In this study, we concentrate on examining possible long-term implications for child cognitive development.
Cesarean birth may be directly and indirectly associated with negative child cognitive outcomes.
The indirect association may occur through established links between cesarean birth and adverse child health outcomes, including asthma, type I diabetes, allergies9–11 and obesity12 that are also associated with impaired functioning and lower academic performance13, 14.
The surgical nature of cesarean procedures also poses postnatal maternal health risks15, with potential knock-on effects for the child’s development through altered mother-child interactions16 and lower rates of breastfeeding17–19.
The direct association may occur through alterations to the infant’s gut microbiota.
Unlike vaginally-born children whose gut is seeded by passing through the birth canal, the gut of cesarean-born children is seeded through contact with the mother’s skin and hospital surfaces.
The result is long-term compositional differences in gut microbiota by mode of birth20–24, with differences observed up until age seven24.
Recently uncovered chemical signaling from the gut microbiota to the central nervous system, affecting memory, motivation, mood and stress reactivity, raises questions about the long-term cognitive effects of disturbed microbiota composition at a sensitive time in brain development25, 26.
Although causal impacts on child development are yet to be proven, altered signaling from disturbed gut microbiota is thought to be a possible driver of higher rates of cognitive disorders, especially autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), among cesarean-born children (see Curran et al.27 for a review).
In animal studies, there is mounting (and replicated) evidence of long-term cognitive impacts from early microbiota disturbance.
These studies show that rodents lacking all gut bacteria from birth (germ-free animals) have memory deficits28 and behavioral abnormalities29, 30 when compared to animals with normal gut microbiota.
Interestingly, these cognitive deficits in rodents can be corrected through the colonization of the intestine via a fecal transplant from the control group, but only if it occurs early in life.
The implication is that there is a critical window to correct any disruption to the gut microbiota, after which cognitive impacts are permanent25.
In this study, we estimate the relation between cesarean birth and child cognitive outcomes using data from the Longitudinal Study of Australian Children (LSAC), a nationally representative birth cohort surveyed biennially, and multivariate regression techniques.
To the best of our knowledge, only Bentley et al.31 has examined the relation between cesarean birth and cognitive outcomes.
Using Australian hospital records linked to teacher-based assessments in the first year of school, they found a significant negative association across several developmental domains.
We build on this study and that of previous health studies in several ways. First, we build on the work of Bentley et al.31 by using mediation analysis to test to what extent any relation is associated with lower rates of breastfeeding and adverse child and maternal health outcomes.
This is important because it helps to identify the importance of direct effects, such as those related to disturbed gut microbiota and helps identify how widespread any effects may be within the population.
Second, LSAC contains rich longitudinal cognitive test information that enables us to gain an insight into longer-term outcomes that are closely related to early academic achievement, an important predictor of lifelong earnings and health.
These include academic test results that measure: school readiness at 4–5, vocabulary and comprehension at 4–5, 6–7 and 8–9 years, problem solving at 6–7 and 8–9 years and national achievement in numeracy and literacy at 8–9 years.
Third, we more rigorously test the sensitivity of any relation to bias from confounding variables not observed in the data or ‘selection on unobserved covariates’. We do this using two methods — re-estimating on a sub-sample where selection on unobserved covariates is likely to be less of an issue (privately insured births without any observed perinatal risk factors) and by estimating lower-bound estimates under conservative assumptions about the magnitude of selection on unobserved covariates using the Oster32 technique.
This helps to provide some guidance on whether estimated relation is plausibly causal.
More information: María-José González-Valenzuela et al. Type of Delivery, Neuropsychological Development and Intelligence in Twin Births, Frontiers in Psychology (2019). DOI: 10.3389/fpsyg.2019.00972
Journal information: Frontiers in Psychology
Provided by University of Malaga
