New Insights Into VKD: Exploring Maternal Obesity and Neonatal Vitamin K Status

Neonatal vitamin K deficiency (VKD) sits at the foundation of vigilance against VKD bleeding, yet the prenatal factors that shape an infant’s vitamin K status at birth have remained surprisingly underexplored. A new study at Kobe University in Japan brings welcome clarity, suggesting that pre-pregnancy obesity increases the likelihood that a newborn will have VKD.

The investigators examined more than 2400 neonates admitted over five years, each screened at birth by measuring PIVKA-II levels, a sensitive marker of functional VK insufficiency. Among these infants, 64 met criteria for VKD (PIVKA-II ≥1000 mAU/mL before any vitamin K administration). To sharpen comparisons, each case was matched to two controls by gestational age and sex, creating a study cohort of 192 mother–infant pairs.

Notably, pre-pregnancy obesity (BMI ≥25 kg/m²) stood out as the only maternal factor that independently predicted neonatal VKD (odds ratio: 3.97, P <0.001). Additionally, maternal BMI correlated positively with neonatal PIVKA-II levels at day 0 (r = 0.285, P <0.0001), raising compelling questions about the metabolic interplay between maternal adiposity and fetal micronutrient availability.

The authors approached this with curiosity rather than assumption. Vitamin K behaves like its fat-soluble peers, accumulating readily in adipose stores. In adults, obesity reliably predicts lower circulating levels of vitamins D and K, likely due to sequestration effects. This study extends that logic to pregnancy: greater maternal adiposity may trap vitamin K in maternal fat depots, leaving less available for placental transfer.

Several alternative explanations were evaluated, including antenatal corticosteroid use, cesarean delivery, and SGA status, which showed no significant association. Likewise, no differences were observed in maternal biochemical or hematologic parameters. A subgroup of mothers with malnutrition or gastrointestinal disease did show elevated risk, but these cases were too few to shift the overall conclusions.

By identifying maternal obesity as a modifiable risk factor, the authors recommend rethinking neonatal VK prophylaxis as part of a broader perinatal nutritional strategy. Their findings do not yet justify routine antenatal VK supplementation in obese pregnancies; prior trials have shown mixed or insufficient clinical benefit. But the signal is clear enough to warrant closer attention.

It’s important to recognize that this was a single-center, retrospective analysis, and maternal vitamin K levels were not measured directly. Still, the consistency of the associations make a compelling case for further prospective work.

In sum, this study adds an important layer to our understanding of neonatal VKD. It suggests that maternal pre-pregnancy obesity is not merely a background characteristic but a meaningful predictor of neonatal vitamin K insufficiency. For clinicians committed to preventing VKDB, these findings suggest the fetal period may hold untapped potential for targeted, individualized vitamin K management in pregnancies complicated by obesity.

Reference
Masuda Y, Ashina M, Imagawa Y, et al. Prepregnancy obesity is an independent risk factor for neonatal vitamin K deficiency at birth. Nutrition. Published online September 16, 2025. doi:10.1016/j.nut.2025.112954