The background is the observation that babies born by Caesarian have different gut flora than those born vaginally. The interest in gut flora is because many believe it relates causally to some diseases. How do you go about investigating such a problem?
Collectively, these seven women gave birth to five girls and two boys, all healthy. Each of the newborns was syringe-fed a dose of breast milk immediately after birth—a dose that had been inoculated with a few grams of faeces collected three weeks earlier from its mother. None of the babies showed any adverse reactions to this procedure. All then had their faeces analysed regularly during the following weeks. For comparison, the researchers collected faecal samples from 47 other infants, 29 of which had been born normally and 18 by Caesarean section. [emphasis added]