New research, which has been published in the journal Science Advances, explains how giving birth through a cesarean delivery may lead to weight gain in the offspring.
The World Health Organization (WHO) recommend that the total number of cesarean deliveries does not exceed 15 percent of live births.
Most cesarean deliveries are required to save the life of either the mother or the baby. However, they may be recommended for other medical reasons, and mothers sometimes opt for an elective surgery.
All in all, recent years have seen an increase of 50 percent in cesarean surgeries worldwide. In the United States, it is estimated that almost a third (or 32.5 percent) of all live births are through a cesarean delivery.
Researchers from the New York University (NYU) School of Medicine in New York City - led by Dr. Maria Dominguez-Bello, a microbiologist at NYU's Sackler Institute - set out to investigate the link between having a cesarean delivery and the weight of the offspring.
The research builds on previous studies that have demonstrated a link between having a cesarean delivery and the risk of obesity in the children. One such recent study reports that children born via cesarean are 15 percent more likely to become obese, and the increased risk is independent of the mother's weight.
But what explains this risk? One theory is that a cesarean delivery interferes with the natural transmission of maternal microbes through the mother's vaginal flora.
Such an early acquaintance with bacteria informs the baby's immune and metabolic systems, preparing them for a healthy adulthood.
While most studies have been observational and pointed merely to an association between weight gain and the delivery method, this study points to a causal mechanism that may explain this association.
The new research was conducted in mice, and, as Dr. Dominguez-Bello notes, it is "the first to demonstrate a causal relationship between [cesarean delivery] and increased body weight in mammals."
Cesarean-born females 70 percent heavier
Dr. Dominguez-Bello and her team compared 34 mice that had been delivered via cesarean with 35 control mice born through their mother's birth canal.
In an attempt to examine the effect of the delivery method on the microbiome of the mice, the researchers extracted and analyzed the DNA of the bacteria found in the offspring.