Eczema is a type of skin hypersensitivity that commonly starts in early childhood, typically at age 3–6 months [1]. Eczema is frequently the first demonstration of atopic disorder to appear in infants, and it can develop into other atopic diseases such as food allergy, asthma, and allergic rhinitis [2,3]. Eczema affects a substantial proportion of children, with a global report of 13.5%–41.9% [4], with a prevalence of 30.48% in China [5]. Despite increasing research on eczema, its etiology has remained unclear in recent years. However, it has been known that eczema development may be influenced by the interaction of genic and environmental factors [6].

Vitamin D, a common lipid-soluble vitamin, not only affects bone development but has also been found to have a potential association with the development of allergic diseases in recent years [7]. It has been shown that low vitamin D status in cord blood increases the risk of childhood eczema [8,9]. The vitamin D levels in neonates and infants are closely associated with maternal vitamin D levels. This correlation is due to the fact that during pregnancy, the maternal vitamin D status and the ability of vitamin D to traverse the placenta play a pivotal role in determining fetal vitamin D levels [10]. Therefore, the connection between prenatal vitamin D levels and infantile eczema is gaining attention. Following that, other birth cohort studies showed contradictory findings on the relationship between infantile eczema concerning maternal vitamin D levels. On the one hand, low maternal vitamin D levels have been found to increase the risk of infantile eczema, allergic rhinitis, asthma, and food allergy in the offspring [7,11]. Increased prenatal vitamin D might protect against childhood asthma and eczema [12]. On the other hand, babies born to moms with high vitamin D status had a higher risk of infantile eczema and food allergies when compared to mothers with low vitamin D status [13,14]. Pregnant women, breastfeeding mothers, and newborns to supplement vitamin D may not reduce the risk of allergy disorders such as allergic rhinitis, asthma, and infantile wheezing [15]. Other partial study shows no relationship between maternal serum vitamin D and infantile eczema [16,17]. A possible mechanism is that vitamin D quiets the adaptive immune system by suppressing the T helper cell type 1 (Th1) and T helper cell type 17 (Th17) cells and favoring regulatory T cells (Treg) [18,19]. In addition, it has been demonstrated that vitamin D can modulate the differentiation and effector functions of Treg cells by PI3K/AKT/mTOR signaling pathway [20].

Currently, there was few epidemiology and mechanism studies on the impacts of prenatal maternal vitamin D status on later infantile eczema, and conclusions remain controversial. Therefore, we first measured the levels of vitamin D in pregnant women by collecting serum samples during pregnancy, and then identified cases of infantile eczema through follow-up assessments conducted 12 months after delivery. The goal of the current study was to investigate the relationship between maternal vitamin D levels and the regulation and functional activity of T-cell transcription factors in newborns, as well as their potential impact on the development of early childhood eczema.