The following report is courtesy of Lily Nichols
Most conversations around bone health tend to focus on calcium or vitamin D, but there’s many more nutrients that factor in.
During pregnancy, your baby’s skeleton is forming and some new research on an understudied nutrient — vitamin K2 — recently came out.
As the years have gone on, there has been more research into vitamin K2, perhaps not as much as vitamin D or iron, but at least something!
One of vitamin K2’s most important functions in the body is in directing minerals (like calcium) into the bones and teeth, and away from soft tissues, where they don’t belong. But K2 is often overlooked in both prenatal nutrition research and supplement formulations. In fact, even today there’s no official RDA for K2 (really!).
A study was recently published on vitamin K2 in pregnancy and how it impacts fetal bone metabolism (PMID: 40452792).
In this 2025 observational study, researchers measured vitamins K2 and D (25-OH D) in mom and baby, plus cord-blood markers of bone metabolism at birth in 197 mother–infant pairs.
Here’s what the researchers found:
K2 deficiency was common: 38.6% of mothers were deficient A significant association was found between maternal vitamin K2 and newborn 25‐OH D levels (if mom was low in K2, baby was often low in D; and the reverse pattern was also observed). Compared with K2-replete mothers, newborns of the K2-deficient group not only had lower 25-OH D, but also had higher osteocalcin and parathyroid hormone levels (PTH) — a pattern consistent with suboptimal bone mineralization
This study reinforces the importance of both vitamin K2 and D for optimal bone health, including in utero. In addition, late-pregnancy K2 deficiency was common, which could affect a baby’s vitamin D status and bone health.
While this study is observational (not proof of cause and effect), and newborn bone density wasn’t directly measured (but rather indicated indirectly via biomarkers), it adds to the growing case for prioritising K2 in prenatal nutrition.
Fortunately, there are a few simple ways to ensure you’re getting at least some K2:
Include K2‑rich foods in pregnancy: egg yolks, aged cheeses, animal fats, organ meats, and/or natto (natto is the only reliable plant source of vitamin K2) Ensure your prenatal includes some K2 (brands I recommend include quality K2) Also a good reminder to keep your vitamin D status on track either through safe sun exposure or quality supplementation.
While research on vitamin K2 is still emerging, the connection to vitamin D and bone metabolism is compelling. And we don’t need to wait for official guidelines to act on emerging evidence. Simply incorporating real food that contains K2 could have a powerful effect on your baby’s lifelong bone health.
The above information emphasises once again the importance of working with a qualified Naturopath before, during and after pregnancy.
