Prepregnancy obesity is an independent risk factor for neonatal vitamin K deficiency at birth

BACKGROUND: Neonatal vitamin K deficiency (VKD) is a known risk factor for vitamin K deficiency bleeding (VKDB), a potentially life-threatening condition. However, maternal risk factors for VKD at birth remain poorly understood. OBJECTIVE: This study aimed to identify maternal factors associated with neonatal VKD at birth, with a focus on prepregnancy obesity. METHODS: We conducted a retrospective matched case-control study of neonates admitted to our hospital between 2018 and 2023. VKD was defined as serum protein induced by vitamin K absence-II (PIVKA-II) levels ≥1000 mAU/mL on day 0 of life before vitamin K administration. For each VKD case, two gestational age- and sex-matched controls were selected. Maternal background characteristics were compared, and multivariate logistic regression was performed to identify independent risk factors for neonatal VKD. RESULTS: Among 64 neonates with VKD and 128 controls, maternal prepregnancy obesity (body mass index ≥25) was significantly more common in the VKD group. Multivariate analysis identified prepregnancy obesity as an independent risk factor for neonatal VKD (odds ratio 3.97, P < 0.001). Additionally, maternal prepregnancy BMI was positively correlated with neonatal PIVKA-II levels at birth (r = 0.285, P < 0.0001). CONCLUSIONS: Maternal prepregnancy obesity is independently associated with an increased risk of VKD in neonates at birth. These findings suggest that targeted evaluation and vitamin K management strategies are warranted in pregnancies complicated by maternal obesity.