Will a C-Section Leave My Baby with Fewer Helpful Antibodies?

Hi Emily. There’s been a Dutch/Scottish study that found that babies born via C-section have half the amount of protective antibodies produced after childhood vaccines than those born vaginally. Is this study good? This feels pretty significant. I was set on a C-section to give birth next time after suffering a serious tear with my first baby, but now I’m worried I’d be putting them at risk to protect my own health.
—Gabi

The study you are referring to is here. In it, researchers took data from a number of babies (either 66 or 101, depending on the vaccine) and measured their degree of antibody response to vaccination. That is: they measured the amount of antibody produced after vaccination with either the pneumococcal or meningococcal vaccines.

They found that there was variation in the concentration of antibodies across individuals based on both their mode of birth and whether they were breastfed or formula-fed. They hypothesize that this response is related to gut bacteria, since gut bacteria also vary along these dimensions.

These results are interesting, and the mechanism is plausible. There is also other recent work which suggests that babies born by C-section are less likely to have a strong immune response to the first dose of the measles vaccine.

Together, these results paint a picture suggesting that birth by C-section might be associated with a lower immune response to antibodies. There are, however, several important caveats.

First, none of these studies are randomized, and some of the results are a little confusing (the first paper finds that antibody responses are lowest in vaginally-born, formula-fed babies, but it’s not clear why this would be). The combination of these facts makes us worry that something else is driving the results other than a causal relationship.

Second — more importantly — it’s not clear these differences have any practical importance. In the first paper, the average antibody levels in all the groups are sufficient to prevent disease. Despite the breathless headlines, it is not the case that any of these groups did not show a significant and robust antibody response. In the case of measles vaccines, the second dose of the vaccine produces a robust response across the board.

Bottom line: this should not impact your choice of birth mode. It’s an interesting fact, possibly worthy of some follow-up as we seek to better understand the microbiome. Not worth changing behavior for.