Seasonal variation of serum 25(OH) vitamin D levels in maternal and umbilical cord blood in Japanese women

Vitamin D status and the adequacy of its supplementation during the first year of life in preterm infants in northern Japan

BACKGROUND

Vitamin D (VD) deficiency (VDD) is a major concern in preterm infants. The prevalence of VDD in mothers and infants varies between countries and is affected by a range of factors, such as geography and lifestyle. Thus, strategies aimed at preventing VDD must consider the status of each region. However, few reports have explored VDD in preterm infants in Japan and the safety and efficacy of VD supplementation in addressing VDD remain unclear.

METHODS

This study was conducted between September 2019 and October 2022. The participants were 108 preterm infants who were divided into three groups based on their gestational age: <28 weeks (Group 1), 28-33 weeks (Group 2), and 34-36 weeks (Group 3). VD status at birth was assessed, and 25-hydroxyvitamin D (25OHD) levels and biochemical markers were monitored during supplementation with 400 IU/day of VD over the first year of life.

RESULTS

Levels of 25OHD at birth were 10.0 (10.0-16.1), 10.5 (10.0-18.0), and 13.0 (10.0-19.0) nmol/L in Groups 1, 2, and 3, respectively. Infants in all three groups exhibited marked VDD. Their 25OHD levels gradually increased with VD supplementation before plateauing at 6 months. Nevertheless, VDD persisted in the majority of infants at 1 month of age. Serum intact parathyroid hormone levels peaked at 1 month of age and declined thereafter, negatively correlating with 25OHD levels. None of the infants exhibited symptoms of VD toxicity.

CONCLUSION

Preterm infants in northern Japan exhibited substantial VDD, regardless of gestational age. In our cohort, VD supplementation at 400 IU/day safely increased 25OHD levels. However, VD levels improved gradually over the months, and several of these infants developed secondary hyperparathyroidism. Further studies are warranted to determine the optimal VD supplementation dose for preterm infants in this region.

Vitamin D concentration in maternal serum during pregnancy: Assessment in Hokkaido in adjunct study of the Japan Environment and Children's Study (JECS)

BACKGROUND

Vitamin D is an essential nutrient for maintaining blood calcium and phosphorus levels and controlling bone density. Deficiency in it leads to rickets, osteomalacia, osteoporosis, and various other diseases. Recently, it has gained attention for reportedly reducing the risk of COVID-19 severity. However, there are no reports evaluating pregnant women in the Hokkaido region of Japan. This study aims to elucidate the current status of vitamin D levels in pregnant women in the Hokkaido region.

METHODS

This study measured the serum concentrations of Vitamin D2 and D3 in 206 pregnant women participating in the Japan Environment and Children's Study-Hokkaido sub-cohort at the Hokkaido Regional Center. It analyzed the relationship between these concentrations and the months, seasons, and sunshine hours.

RESULTS

The mean maternal age was 31.7 ± 4.7 years, and the mean prepregnancy BMI was 21.0 ± 2.5 kg/m2. Only two women have given birth at least once. Regarding sunscreen use, 65 participants (31.6%) responded "often" or "sometimes." Five women used the supplement containing Vitamin D. The value of 25(OH)D2 was above 1 ng/ml in four of them. The average 25(OH)D3 level was 12.1 ng/ml, with a median of 11.0 ng/ml. Four participants (1.9%) had levels below 5 ng/ml. The highest median of 25(OH)D3 was in July, and the lowest was in April. The concentration of 25(OH)D3 was significantly higher in summer than in winter. A correlation was found between 25(OH)D3 and sunshine hours, with 25(OH)D3 concentrations gradually increasing as sunshine hours increase.

CONCLUSION

It was found that almost all pregnant women in Hokkaido were deficient in vitamin D. It is necessary to implement measures to enhance vitamin D levels in pregnant women to safeguard the health of women and fetuses in Hokkaido.

Seasonal Serum 25(OH) Vitamin D Level and Reproductive or Immune Markers in Reproductive-Aged Women with Infertility: A Cross-Sectional Observational Study in East Japan

Several studies have reported that vitamin D may modify human reproductive functions; however, the results are conflicting. We aimed to comprehensively evaluate serum vitamin D levels and examine the relationship between serum vitamin D levels and ovarian reserve markers, and immune markers of implantation, in reproductive-aged Japanese women with infertility.in reproductive-aged women with infertility. This cross-sectional, single-center study included reproductive-aged women who underwent preconception screening for fertility. Serum vitamin D levels and reproductive and immune markers were measured. Standard and advanced statistical techniques were used. We observed a statistically significant difference in the seasonal and monthly 25(OH) vitamin D levels; the 25(OH) vitamin D level during winter was the lowest among all seasons. However, there was no linear correlation between 25(OH) vitamin D levels and ovarian reserve markers, such as follicle-stimulating hormone and anti-Müllerian hormone, or the Th1/Th2 cell ratio, which is used as an implantation-related immunological marker. In this large-scale study, we evaluated the serum 25(OH) vitamin D concentration in reproductive-aged women with infertility in Japan; however, there was no association between reproductive function and vitamin D levels.

Umbilical Cord Blood-Derived Exosomes in Maternal-Fetal Disease: a Review

The nutrients and other factors transported by umbilical cord blood, which is vital for fetal survival, play crucial roles in fetal development. There are various communication modes between the fetal-placental system and the maternal-placental system, and these communication modes are all mediated by umbilical cord blood. During the process of umbilical cord blood transportation, the changes of some nutrients and factors may play a key role in fetal development. Exosomes, which are members of the extracellular vesicle family, are present in the umbilical cord blood and play roles in information transmission as a result of their efficient cellular communication activity. The study of umbilical cord blood-derived exosomes provides a new approach for research on the etiology of maternal-fetal diseases and they may be useful for the development of intrauterine treatments. This review summarizes specific functions and research directions regarding umbilical cord blood-derived exosomes, and their potential associations with pregnancy complications.

Ineffectiveness of antenatal guidance intervention for vitamin D insufficiency and deficiency in pregnant women in Kyoto, Japan

AIM

The aim of this study was to investigate the vitamin D status among healthy pregnant women in Japan, and to evaluate the effectiveness of the antenatal health guidance intervention for the pregnant women who were informed about their low vitamin D levels.

METHODS

We measured the level of 25-hydroxyvitamin D (25[OH]D) using chemiluminescent immunoassay among the singleton pregnant women who received at antenatal routine check-up (8-24 weeks of gestation) with written consent during September 2017-September 2018. The measurement values were informed by the concerned physician and health guidance intervention was given to the pregnant women with inadequate Vitamin D status (25[OH]D < 30 ng/mL). At around 36 weeks of gestation, the measurement of 25(OH)D and a questionnaire regarding behavioral changes after the guidance was conducted.

RESULTS

The average value of 25(OH)D of 1192 pregnant women before the guidance was 14.89 ± 4.85 ng/mL, and the prevalence of sufficient vitamin D status (25(OH)D ≥ 30 ng/mL) was 0.67% (8/1192). Nine hundred eighty-two pregnant women who had inadequate vitamin D status were followed, thereafter-guidance prevalence of sufficiency was 1.02% (10/982); insufficiency, 14.66% (144/982); and deficiency, 84.32% (828/982), respectively. Although the prevalence of deficiency was decreased after guidance intervention significantly, the prevalence was still high and the effect on behavioral changes was a little.

CONCLUSION

The prevalence of vitamin D sufficient status among pregnant women in Japan was extremely low, which is a serious condition. It was also revealed the effectiveness of the antenatal health guidance intervention for pregnant women was not enough.

Vitamin D: Current Challenges between the Laboratory and Clinical Practice

Vitamin D is a micronutrient with pleiotropic effects in humans. Due to sedentary lifestyles and increasing time spent indoors, a growing body of research is revealing that vitamin D deficiency is a global problem. Despite the routine measurement of vitamin D in clinical laboratories and many years of efforts, methods of vitamin D analysis have yet to be standardized and are burdened with significant difficulties. This review summarizes several key analytical and clinical challenges that accompany the current methods for measuring vitamin D. According to an external quality assessment, methods and laboratories still produce a high degree of variability. Structurally similar metabolites are a source of significant interference. Furthermore, there is still no consensus on the normal values of vitamin D in a healthy population. These and other problems discussed herein can be a source of inconsistency in the results of research studies.

Association between umbilical cord vitamin D levels and adverse neonatal outcomes

Objective

We investigated the associations between cord blood concentration of 25-hydroxyvitamin D [25(OH)D], neonatal outcomes, and the risk of hospitalization during the first year of life.

Methods

A total of 402 newborn infants and their mothers were prospectively enrolled and divided in four groups according to season of the year. We determined 25(OH)D serum concentrations from maternal–neonatal pairs at delivery by electrochemiluminescence immunoassay. Cut-offs at 25, 50, and 75 nmol/L defined vitamin D status, corresponding to deficiency, insufficiency, and sufficiency, respectively. Crude odds ratio (cOR) and 95% confidence intervals (CI) were estimated using logistic regression.

Results

Vitamin D severe deficiency (i.e., <25 nmol/L) was present in 18% of newborns. Cord blood severe deficiency was associated with an increased risk of preterm birth (cOR 3.6, 95% CI: 1.1–12.2), neonatal respiratory distress syndrome (cOR 5.9, 95% CI: 1.1–33.2), and increased risk of hospitalization during the first year of life because of acute respiratory infection (cOR 3.9, 95% CI: 1.4–10.6) or acute gastroenterocolitis (cOR 5.2, 95% CI: 1.4–19.1).

Conclusion

Cord blood vitamin D deficiency is associated with increased risk of preterm birth, neonatal respiratory distress syndrome, and hospitalization during the first year of life.

Changes in vitamin D status considering hemodilution factors in Japanese pregnant women according to trimester: A longitudinal survey

Objectives

There have been no longitudinal surveys on the changes in 25-hydroxyvitamin D [25(OH)D] while considering hemodilution factors among pregnant Japanese women. Therefore, we examined 25(OH)D levels as well as red blood cell count (RBC), hemoglobin (Hb), and Hematocrit (Hct) at the three trimesters among pregnant Japanese women to determine the distribution of serum 25(OH)D levels and the influence of hemodilution.

Design

This was a longitudinal study.

Setting

The study was conducted at Ibaraki Seinan Medical Center Hospital in Japan.

Participants

The participants comprised 50 women in the first trimester with singleton pregnancies and without any complications.

Outcome measures

Participants were recruited from June to August 2018, and followed up till their postpartum period. Blood samples were collected at the first, second, and third trimesters, i.e., at 4–15, 16–27, and 28–39 weeks, respectively. 25(OH)D levels, RBC, Hb, and Hct were analyzed across the three trimesters.

Results

Comparing the first, second, and third trimesters, 25(OH)D, RBC, and Hb were significantly declined in the second and third trimesters (p < 0.001). According to Spearman’s correlation coefficient with 25(OH)D and RCB, Hb, Hct, significant correlations were found between 25(OH)D and Hb (p < 0.001), as well as Hct (p < 0.001) in the third trimester.

Conclusions

The present study had two major findings. First, it showed that the vitamin D status of most pregnant Japanese women were considered as vitamin D deficient. Second, the maternal serum 25(OH)D levels, RBC, Hb, and Hct of the pregnant women declined in the second and third trimesters. Thus we propose to have routine screening of vitamin D status of pregnant women, especially in the second trimester.