People will do just about anything for their kids. And for some parents of babies born by Caesarean section, that includes swabbing a baby with bacteria from their mother’s vagina. It’s a new idea, but it’s catching on—despite the fact that there’s no evidence that it helps, as several doctors note in the British Medical Journal (BMJ). 

The practice is called “vaginal seeding,” and aims to bolster a newborn’s health with the helpful starter bacteria he or she might have missed by skipping the birth canal. Microbiome is the collective term for the ecosystems of bacteria, fungi, and viruses living on and in your body. As you’ve probably heard by now, not all microbes are bad. In fact, you need a certain diversity and balance of microbes to keep your body functioning. You pick up these microbes everywhere you go, from the doorknob of a hotel room to kissing a friend on the cheek. Most people get their first microbial download as they enter the world. But C-section babies don’t. 

The concept seems sound enough. But, as the authors of the BMJ editorial explain, there’s simply no evidence that vaginal seeding is actually effective or safe.

"Demand for this process has increased among women attending hospitals in the UK—but this has outstripped professional awareness and guidance,” co-author Aubrey Cunnington said in a press statement. “At the moment we're a long way from having the evidence base to recommend this practice. There is simply no evidence to suggest it has benefits—and it may carry potential risks." 

Swabbing a baby transfers all kinds of microbes, both harmful and helpful. And since there’s no catalog of which bacteria are being shared, there’s no way of knowing which pathogens might be causing a baby’s sickness down the line. 

"In some countries, including the UK, we don't test pregnant women for the bacteria group B streptococcus,” Cunnington continued. “This is carried by around one in four pregnant women, and although it poses no risk to the mother, it can cause fatal infections in babies. There are also other conditions that cause no symptoms in the mother, such as chlamydia, gonorrhea, and herpes simplex virus that could be transferred on the swab. One colleague had to intervene when a mother with genital herpes, who had undergone a Caesarean section, was about to undertake this process. Swabbing would have potentially transferred the herpes virus to the baby." 

Hospital staff will also not expect a C-section baby to be vulnerable to the kinds of infections as a baby born of vaginal delivery. “It's important [that] parents tell staff they have performed the procedure, so the healthcare team are aware the baby is at risk of the same infections as a baby born by vaginal delivery," Cunnington added.

The bottom line is that parents and physicians should wait for more data before whipping out the swabs. In the meantime, Cunnington says, they can focus on evidence-based methods of boosting a baby’s microbiome: "Encouraging breast feeding and avoiding unnecessary antibiotics may be more important to a baby's gut bacteria than worrying about transferring vaginal fluid on a swab."