Inherited excess weight: intestinal microbiota and mode of delivery act in concert
A mother can transmit her excess weight to her child. Canadian researchers describe how the mode of delivery and certain modifications of the child’s intestinal microbiota could act together in this weight transfer.
Children born to a mother who is herself overweight or obese (OWOB) before pregnancy have at least twice the risk of being themselves OWOB. This risk is increased by 30% when the child is delivered by cesarean section, which is more common in OWOB women. According to several studies, this transmission of the OWOB phenotype takes place through the mother’s intestinal microbiota, and is thought to be impacted by the mode of delivery.
Cesarean section: an increased risk
A Canadian team tested these hypotheses by monitoring 935 pregnancies in a Canadian cohort for 3 years. The following data were collected: BMI of the expectant mothers before they were pregnant, the children’s Z-score (BMI measurement adjusted for infantile obesity) at 1 and 3 years of age, fecal samples from newborns between 3 and 4 months old, and data relating to the mode of delivery. After adjustment to eliminate other factors (tobacco, gender of the child, socio-economic status…), the results are clear: children born to an OWOB mother had a 3.33-fold greater risk of being OWOB at one year of age if they were born by vaginal delivery, and an almost 5-fold greater risk if they were delivered by C-section. The risk was greater still in cases where an emergency cesarean was performed. At three years of age, the risk was similar to that observed initially.
Discovery of the impact of Firmicutes
The team also combined the analysis of the children’s intestinal microbiota with a statistical method not previously published in connection with microbiota research: sequential mediation analysis, whose aim is to determine how a specific variable (here the weight of the mother before pregnancy) affects another variable (having a child who is OWOB at one and three years of age). It appeared that the excess weight was transmitted from the mother to her child through increased levels of bacteria belonging to the Firmicutes branch in the infantile intestinal microbiota, in particular those from the Lachnospiraceae family. These increased levels were more pronounced in OWOB children born by cesarean section to an OWOB mother, with a greater presence of Cryptococcus (bacteria observed more frequently in obese individuals, including OWOB women at the beginning of pregnancy.
Transmission of an obesogenic microbiota
Finally, the genera Acinetobacter, Bacteroides, Collinsella, Megasphaera, Finegoldia, Peptoniphilus and the Peptostreptococcaceae family were more abundant in OWOB children born by vaginal delivery to an OWOB mother: for the most part, as the authors emphasize, bacteria that produce short-chain fatty acids promoting gluconeogenesis and fat storage. The mothers’ weight before pregnancy would therefore affect their children through the transmission of an obesogenic microbiota, whose dysbiosis seems to be exacerbated by cesarean delivery. The intergenerational transmission pathway of the OWOB trait is thought to be mediated by the mode of delivery and abundance of Lachnospiraceae. The role of the mother’s microbiotas (intestinal, vaginal, and cutaneous) in this transmission warrants more extensive studies to try to resolve the global obesity epidemic.
Tun HM et al. Roles of Birth Mode and Infant Gut Microbiota in Intergenerational Transmission of Overweight and Obesity From Mother to Offspring. JAMA Pediatr. 2018; Feb 19.