Would be great if those who disagree could dispassionately say why.

If this study had never been done, we’d still have tons of evidence in support of the practice of vaginal fluid inoculation. The effect size for auto-immune diseases, gut microbiome, and immune system development, is surprisingly large, even for those clinical entities that develop later in life like IBD (with peak incidence in the mid 20s and mid 40s, and no clinical signs or symptoms in childhood). Caesarian births and breastfeeding status are important risk factors for food allergies too.

Whether you had a vaginal or caesarian birth has some impacts on your gut microbiome that outweigh your dietary choices in adulthood— that is well-known and very surprising!

That we measure any effect at all on cognitive development milestones is really remarkable as well— I wouldn’t take these specific findings too seriously (and obviously you don’t decide to not get a caesarian for the odd probability of marginally faster cognitive development, and caesarians are typically done in contexts where the risks are measured in terms of life or death), but considering the wealth of adjacent data we already have, yes there is gold to be found here. Even if it’s not what we think it is, there’s something interesting to be found, and more work in this direction is needed.

Although these studies are not rare: this is a very active area of research, for good reason! To dismiss this flippantly as “needing no further investigation” is not to be a healthy skeptic: instead, it is to ignore the veritable boom in the scientific/medical literature on the subject over the last two decades or so.