Maternal Vitamin D Status and Its Related Factors in Pregnant Women in Bangkok, Thailand

Vitamin D levels and its influencing factors in pregnant women in mainland China: A systematic review and meta-analysis

OBJECTIVE

Maternal vitamin D deficiency is a prevalent public health issue worldwide. While isolated reports from certain cities in China have highlighted the existence of maternal vitamin D deficiency, no nationwide investigation has been conducted on this topic. Therefore, we conducted a meta-analysis and systematic review to examine the prevalence and associated influencing factors of maternal vitamin D deficiency in mainland China. This study aims to provide a theoretical foundation for future prevention and supplementation strategies for maternal vitamin D.

METHODS

We retrieved relevant Chinese and English literature on the status of maternal vitamin D deficiency in mainland China from databases such as CNKI, Wanfang Data, VIP, CBM, Web of Science, Google Scholar, and PubMed. The literature search and database construction were conducted until September 8, 2023. Data were extracted and synthesized following PRISMA guidelines.After literature screening and quality assessment, we performed meta-analysis, sensitivity analysis, and identified publication bias using RevMan 5.3 software.

RESULTS

A total of 26 articles were reviewed, involving 128,820 pregnant women. Among them, 108,768 had vitamin D insufficiency or deficiency, resulting in a prevalence of 84% (95% CI: 81%~88%). Subgroup analysis revealed the highest prevalence of vitamin D deficiency or insufficiency among pregnant women in mainland China to be in the northwest region (94%, 95% CI: 94%~95%). Furthermore, the highest prevalence was observed during the winter and spring seasons (80%, 95% CI: 77%~83%) and in the early stages of pregnancy (93%, 95% CI: 90%~95%). Significant statistical differences (P<0.05) were found among these three subgroups. No publication bias was detected, and sensitivity analysis indicated the stability of the meta-analysis outcome.

CONCLUSION

This study provides evidence of the prevalence of vitamin D deficiency or insufficiency among pregnant women in mainland China. To improve the overall health and well-being of the population, relevant health authorities should develop policies aimed at alleviating this phenomenon.

Vitamin D status in non-pregnant women of reproductive age: a study in Southern Thailand

Vitamin D inadequacy is a global problem in all age groups. Although there are various studies of vitamin D status in pregnant women in Southeast Asia, to date there are few studies from Southeast Asia examining vitamin D status in non-pregnant women of reproductive age. To examine the prevalence of vitamin D insufficiency (VDI) in healthy non-pregnant women of reproductive age in Southern Thailand, 120 healthy non-pregnant women aged 18-42 years were enrolled. Demographic and lifestyle data relevant to vitamin D assessment (sunlight exposure, nutritional intake, type of dress, sunscreen use) and biochemical studies (serum 25-hydroxyvitamin D or 25OHD, parathyroid hormone, calcium, phosphate) were obtained. VDI was classified as serum 25OHD < 20 ng/mL. The average serum 25OHD level was 23.1 ± 6.0 ng/mL. The overall prevalence of VDI was 34.1%. The average dietary intake of calcium, phosphorus and vitamin D and the average duration of sunlight exposure per week were not significantly different between the VDI women and the vitamin D sufficient (VDS) women. Logistic regression analysis found that the significant risk factors for VDI were greater body mass index and higher family income (p-values 0.01 and 0.02, respectively). The prevalence of VDI in non-pregnant women was high at 34%. As the dietary sources of vitamin D are limited and cutaneous vitamin D synthesis is limited by avoidance of sunlight exposure, vitamin D fortification in common daily foods would be an alternative option to reach the recommended vitamin D intake generally of at least 800 IU/day.

Estimation of the vitamin D (VD) status of pregnant Japanese women based on food intake and VD synthesis by solar UV-B radiation using a questionnaire and UV-B observations

Although vitamin D (VD; serum 25 hydroxyvitamin D) deficiency (< 20 ng/mL) is widespread among Japanese women, the VD status among pregnant women is unknown. This study aimed to determine the VD status of pregnant Japanese women during different meteorological seasons and to determine the factors controlling VD status. A total of 309 pregnant Japanese women were recruited at 28 weeks of gestation at the gynecology department of a university hospital in Tokyo between August 2018 and October 2019. Blood samples were collected to measure serum 25(OH)D levels. Two questionnaires were completed: a brief self-administered dietary history questionnaire (BDHQ) and an outdoor exposure history questionnaire to determine skin sunlight exposure and the use of sunscreen. Among the recruited subjects, 268 were included in the statistical analysis. The average VD intake from food was 9.0 μg/day, the average VD synthesis from UV-B was 15.2 μg/day, and the average sum of VD intake and nominal VD synthesis was 24.1 μg/day; this exceeded the recommended 2011 Dietary Reference Intake for the USA and Canada (15.0 μg/day). However, the average serum 25(OH)D level (11.4 ng/mL) was very low, indicating widespread VD deficiency. Serum 25(OH)D and VD synthesis by solar UV-B were significantly correlated only during the high UV-B season. The 25(OH)D level was weakly correlated with the VD intake from food in all seasons. We obtained a statistically significant correlation between serum 25(OH)D level and VD intake from food using the BDHQ. We also obtained a statistically significant correlation between the serum 25(OH)D level and VD synthesis from solar UV-B exposure, especially during the high UV-B season. Our logistic regression analysis model predicted VD deficiency in 88.0% of subjects. Our method might be possible to be used to predict the VD status of pregnant Japanese women, although another validation cohort is needed to verify the ability of the estimation equation.

Maternal vitamin D status in early pregnancy and its association with gestational diabetes mellitus in Shanghai: a retrospective cohort study

Background

There is growing interest regarding vitamin D and its potential role in gestational diabetes mellitus (GDM). We aimed to assess maternal vitamin D status in early pregnancy and its relationships with the risk of GDM in a Chinese population in Shanghai.

Methods

The retrospective cohort study included a total of 7816 pregnant women who underwent a 75-g oral glucose tolerance test (OGTT) during 24–28 weeks of gestation. Participants’ demographic information including maternal age, prepregnancy body mass index (BMI), gestational age, parity, season of blood collection, serum 25-hydroxy vitamin D [25(OH)D] data and other blood biomarker data at 6 to 14 weeks of gestation were retrospectivly extracted from the medical records in the hospital information system.

Results

In the cohort, the prevalence of GDM was 8.6% and the prevalence of vitamin D deficiency and insufficiency in early pregnancy was 53.1 and 38.5%, respectively. The mean value of the serum 25(OH)D concentration was 19.6±7.5 ng/mL. The restricted cubic splines model showed an inverted J-shaped relationship in which the risk of GDM decreased when the 25(OH)D concentrations were ≥ 20 ng/mL. Logistic model analysis showed that 25(OH)D concentrations ≥ 30 ng/mL significantly decreased the risk of GDM (odds ratio = 0.63, 95% confidence interval: 0.45-0.89; P = 0.010) compared with 25(OH)D concentrations < 20 ng/ml.

Conclusions

In early pregnancy, vitamin D deficiency and insufficiency were very common, and a high level of vitamin D showed protective effects against the incidence risk of GDM.

Vitamin D deficiency in South-East Asian children: a systematic review

OBJECTIVE

To describe the prevalence and determinants of vitamin D deficiency (VDD) among healthy children aged between 0 and 18 years living in South-East Asia (SEA).

DESIGN

We systematically searched Ovid MEDLINE and Ovid EMBASE for observational studies assessing VDD among healthy children in the SEA region as the primary or secondary outcome from database inception to 6 April 2021. PubMed was used for e-pubs and publications not indexed in Medline. Publications that included abstracts in English were included. We performed a systematic review to describe the prevalence of VDD in SEA children.

RESULTS

Our initial search identified 550 publications with an additional 2 publications from manual screening. Of those, 21 studies from 5 different countries (Thailand, Indonesia, Vietnam, Malaysia and Cambodia) were summarised and included in forest plots. The prevalence of VDD (<50 nmol/L) ranged from 0.9% to 96.4%, with >50% of newborns having VDD, and severe VDD (<30 nmol/L) ranged from 0% to 55.8%. Female sex and urban living were the most common determinants of VDD.

CONCLUSIONS

VDD among healthy children living in the SEA region is common. Efforts to detect VDD and the implementation of preventive measures, including education on safe sun exposure and oral vitamin D supplementation or food fortification, should be considered for key target groups, including adolescent females and pregnant and lactating women to improve the vitamin D status of newborns.

PROTOCOL REGISTRATION NUMBER

This study is registered with PROSPERO (CRD42020181600).

Relationship between Maternal Vitamin D Levels and Adverse Outcomes

Vitamin D (VD), a fat-soluble vitamin, has a variety of functions that are important for growth and development, including regulation of cell differentiation and apoptosis, immune system development, and brain development. As such, VD status during pregnancy is critical for maternal health, fetal skeletal growth, and optimal pregnancy outcomes. Studies have confirmed that adverse pregnancy outcomes, such as preeclampsia, low birth weight, neonatal hypocalcemia, poor postnatal growth, skeletal fragility, and increased incidence of autoimmune diseases, can be associated with low VD levels during pregnancy and infancy. Thus, there is growing interest in the role of VD during pregnancy. This review summarizes the potential adverse health outcomes of maternal VD status during pregnancy for both mother and offspring (gestational diabetes mellitus, hypertensive gestational hypertension, intrauterine growth restriction, miscarriage, stillbirth, and preterm birth) and discusses the underlying mechanisms (regulation of cytokine pathways, immune system processing, internal secretion, placental function, etc.) of VD in regulating each of the outcomes. This review aims to provide a basis for public health intervention strategies to reduce the incidence of adverse pregnancies.

Maternal Vitamin D Status and Its Associated Environmental Factors: A Cross-Sectional Study

BACKGROUND

Vitamin D deficiency is common among women during pregnancy. This study aims to determine the prevalence of vitamin D deficiency and their shared modifiable environmental factors among pregnant women in Indonesia and Malaysia.

METHODS

Blood samples of 844 third-trimester pregnant women (Indonesians: 311; Malaysians: 533) were collected to determine their serum 25(OH) D levels. Information on sun exposure and sun protection behaviours were obtained through face-to-face interviews. Dietary vitamin D intake was assessed by using a semiquantitative food frequency questionnaire.

RESULTS

The prevalence of vitamin D deficiency (<30 nmol/L) among Indonesian and Malaysian pregnant women were 42.4% and 72.0%, respectively. Percentage of exposed body surface area was inversely associated with vitamin D deficiency among Indonesian pregnant women (OR = 0.21, 95% CI = 0.09-0.48). Among Malaysian pregnant women, higher intakes of dietary vitamin D were associated with lower risk of vitamin D deficiency (OR = 0.48, 95% CI = 0.29-0.81). Analysis of the combined cohorts revealed a lower risk of vitamin D deficiency among pregnant women who had a daily intake of at least 15 mcg vitamin D (OR = 0.58, 95% CI = 0.38-0.88) and exposure of more than 27% body surface area to the sunlight (OR = 0.30, 95% CI = 0.16-0.60).

CONCLUSIONS

Despite abundant sunshine, vitamin D deficiency is prevalent among pregnant women in tropical countries. The present study suggests that nutrition education on vitamin D intake and sun exposure during pregnancy is necessary for primary prevention of vitamin D deficiency in pregnant women living in the tropical countries.

Effect of PM2.5 exposure on Vitamin D status among pregnant women: A distributed lag analysis

BACKGROUND

Serum vitamin D levels are associated with exposure to air pollution, however, the lagged effect of exposure to air pollution remains unknown in pregnant women.

METHODS

Pregnant women who delivered at a maternity center in Shanghai, China, from 2015 to 2019 were included in the present study. The concentration of particulate matter 2.5 (PM_2.5) before 25-Hydroxyvitamin D [25(OH)D] detection was estimated using the satellite-based grid models. The distributed lag non-linear models were performed to examine the lagged association between weekly-specific PM_2.5 exposure and vitamin D deficiency (VDD) or serum 25(OH)D levels.

RESULTS

Among the 58,025 pregnant women included in the study (mean age at conception, 30.77 ± 3.75 years; mean prepregnancy BMI, 21.09 ± 2.55 kg/m²), 61.32% were diagnosed with VDD. Weekly-specific PM_2.5 exposure at weeks 1-10 before the detection of 25(OH)D was significantly associated with an increased incidence of VDD (p < 0.05). For every 10 μg/m³ increase in PM_2.5 exposure, the serum 25(OH)D level decreased by 1.346 nmol/L (95%CI: 1.183-1.508 nmol/L). The association between average PM_2.5 exposure and VDD at 1-10 weeks was more significant in weather conditions with low mean sunshine hours (OR: 1.246, 95%CI: 1.221-1.271).

CONCLUSION

Our study provided suggestive evidence that PM_2.5 exposure at 1-10 weeks before the 25(OH)D detection may decrease the circulating 25(OH)D levels in pregnant women and increase VDD risk in pregnant women. More attention should be paid to the long-term impact of PM_2.5, in particular, during weather conditions with a relatively short duration of sunshine.

Predictors of 25-hydroxyvitamin D concentrations during pregnancy: A longitudinal analysis in the Brazilian Amazon

OBJECTIVES

To determine predictors of 25-hydroxyvitamin D₃ (25(OH)D₃) concentrations (25^th, 50^th, and 75^th percentiles) in the third trimester of pregnancy.

SUBJECTS/METHODS

Data on sociodemographic, obstetric, lifestyle and pregnancy characteristics, including serum 25(OH)D₃ and retinol, were collected among 448 pregnant women who participated in the Maternal and Child Health and Nutrition in Acre, Brazil (MINA-Brazil Study) in Cruzeiro do Sul, Brazilian Amazon (latitude 7°S). Simultaneous-quantile regression was fitted to prospectively assess predictors at the 25^th, 50^th and 75^th percentiles of 25(OH)D₃ concentrations.

RESULTS

In the third trimester, 25(OH)D₃ <50 nmol/L was observed in 26% of pregnant women. Exposure to the Amazonian dry season during follow-up and vitamin D status ≥75 nmol/L in the second trimester of pregnancy were positively associated with 25(OH)D₃ concentrations in the third trimester. Pregnant women who were the main providers of family income presented lower 25(OH)D₃ concentrations (50^th and 75^th percentiles: -15 nmol/L, 95%CI -24; -3, p = 0.02, and -22 nmol/L, 95%CI -36; -7, p = 0.004, respectively), as well as those with sustained vitamin A insufficiency (25^th and 50^th percentiles: -27 nmol/L, 95%CI -40; -15, p < 0.001, and -17 nmol/L, 95%CI -33; -1, p = 0.04, respectively). Sun protection practices had a smaller negative impact on 25(OH)D₃, restricted to participants whose concentrations were at the 25^th percentile of the distribution.

CONCLUSIONS

Seasonality and vitamin A status were important predictors of 25(OH)D₃ concentrations in the third trimester. Adequate exposure to sunlight and dietary sources of vitamin A within safe intake levels may help ensuring a good nutritional status of vitamin D during pregnancy.

Vitamin D status in full-term exclusively breastfed infants versus full-term breastfed infants receiving vitamin D supplementation in Thailand: a randomized controlled trial

Background

Many international medical organizations recommend vitamin D supplementation for infants, especially exclusively breastfed infants. In Thailand, however, data regarding the vitamin D status in Thai infants are lacking. Such data would help to support physician decisions and guide medical practice.

Methods

Full-term, exclusively breastfed infants were randomized into two groups at 2 months of age to continue exclusive breastfeeding either without vitamin D supplementation (control group, n = 44) or with vitamin D₃ supplementation at 400 IU/day (intervention group, n = 43) until 6 months of age. At 6 months, the serum vitamin D (25OHD) of the infants and their mothers, serum bone marker, and infants’ growth parameters were compared between the two groups.

Results

The infants’ serum 25OHD concentration was lower in the control group than intervention group (20.57 ± 12.66 vs. 46.01 ± 16.42 ng/mL, p < 0.01). More infants had vitamin D sufficiency (25OHD of > 20 ng/mL) in the intervention group than control group (93.0% vs. 43.2%, p < 0.01). There were no significant differences in the maternal 25OHD concentrations between the control and intervention groups (25.08 ± 7.75 vs. 23.75 ± 7.64 ng/mL, p = 0.42). Serum calcium, phosphorus, intact parathyroid hormone, alkaline phosphatase, and infants’ growth parameters were comparable between the two groups. After adjustment for the confounding factors, 25OHD concentration in the intervention group was 25.66 ng/mL higher than the control group (95% confidence interval, 19.07–32.25; p < 0.001). Vitamin D supplement contributed to an 88.7% decrease in the prevalence of vitamin D insufficiency/deficiency (relative risk, 0.11; 95% confidence interval, 0.04–0.35; p < 0.01).

Conclusions

Most full-term, exclusively breastfed Thai infants have serum vitamin D concentration below sufficiency level at 6 months of age. However, vitamin D supplementation (400 IU/day) improves their vitamin D status and prevents vitamin D deficiency.

Trial registration

The study was pre-registered in the Thai Clinical Trials Registry (TCTR20190622001) on 22/06/2019.

The Association of Maternal Vitamin D Status during Pregnancy and Neonatal Anthropometric Measurements: A Longitudinal Study in Minangkabau Pregnant Women, Indonesia

The prevalence of vitamin D deficiency (VDD) appears to be increasing. VDD during pregnancy has been associated with several adverse pregnancy outcomes. This study aimed to investigate the association between VDD and fetal anthropometric measurement. This prospective cohort study consisted of 232 pregnant women in their first trimester who were recruited at the antenatal clinics and they maintained to be subjects of the study until their delivery time. Serum 25-hydroxyvitamin D (25(OH)D) concentration was measured at first and third trimester using enzyme-linked immunosorbent assay. The prevalence of VDD in the first-trimester was 82.8%. Mean of 25(OH)D concentration in the third-trimester was significantly higher than in the first trimester (14.00 (6.98) vs. 21.22 (10.17) ng/mL). After adjusting age, pre-pregnancy BMI, and gestational age at delivery, it was found that VDD during pregnancy was not significantly associated with neonatal anthropometry (p>0.05). It was concluded that VDD was common in a tropical country. Large, well designed, multicentre observational studies are required to determine whether VDD enhances the risk of adverse pregnancy outcomes.

Pooled estimate of vitamin D deficiency among pregnant women in India: a systematic review and meta-analysis

BACKGROUND

Vitamin D deficiency among pregnant women is a public health concern globally. In India, individual studies report high prevalence. However, lack of national data masks the true burden. This work determined the pooled prevalence of vitamin D deficiency among pregnant women in India through a systematic review of literature and meta-analysis.

METHODS

Three different search engines yielded 15 eligible articles. Study quality was assessed by 10 different criteria and summary of study quality was categorized as per Cochrane standards. Meta-analysis was performed to estimate pooled prevalence of vitamin D deficiency among healthy pregnant women and heterogeneity among selected studies. A sample of n = 4088 was used to study the pooled prevalence among pregnant women.

RESULTS

The random effects combined estimate was 32.35% (95% CI, (12.58-117.48). High heterogeneity (tau² = 0.39, I² = 100%) and high risk of bias was observed among the selected studies. The test for overall effect was observed to be z = 2.54(P = 0.01).

CONCLUSION

Pooled estimate > 30% emphasizes the need for screening through antenatal care services and initiate preventive measures to address the deficiency.

Influence of vitamin D binding protein polymorphism, demographics and lifestyle factors on vitamin D status of healthy Malaysian pregnant women

BACKGROUND

Vitamin D deficiency (VDD) has been related to vitamin D binding protein (GC) gene polymorphism, demographics and lifestyle factors in different populations. However, previous studies only focused on demographic and lifestyle factors or genetic factors alone. Therefore, this cross-sectional study aimed to assess the association between GC gene polymorphism, demographics and lifestyle factors with VDD among Malaysian pregnant women.

METHOD

Information on demographic characteristics, dietary vitamin D intake from supplement and food, time spent outdoors, skin type and clothing were collected using a questionnaire. Plasma total 25-hydroxyvitamin D (25OHD) levels were measured using an Ultra-High-Performance Liquid Chromatography (UHPLC). Maternal GC single nucleotide polymorphisms (SNPs) (rs4588 and rs7041) were determined using restriction fragment length polymorphism (RFLP) technique.

RESULTS

Results showed that 50.2% of pregnant women were vitamin D deficient (25OHD < 30 nmol/L). VDD (25OHD < 30 nmol/L) was significantly associated with age, veiled clothing, maternal vitamin D intakes from both food and supplements, and GC rs7041(and GC diplotypes). In contrast to previous studies that reported for non-pregnant population, a significant positive association was found between CC genotype for SNP GC rs7041, GC 1s-1s and GC If-2 with risk of VDD (25OHD < 30 nmol/L).

CONCLUSIONS

The high prevalence of maternal VDD found in this study suggests the need for urgent development and implementation of vitamin D supplementation or fortification strategies to reduce VDD among pregnant women. The discrepancy in the association between GC rs7041 gene polymorphism and VDD reflects the variation in the factors associated with VDD in pregnancy compared to non-pregnant state.

Prevalence and risk factors of hypovitaminosis D in pregnant Spanish women

The hypovitaminosis D epidemic is a global health problem. Our aim was to assess the prevalence and potential risk factors of hypovitaminosis D among pregnant women on the eastern Mediterranean coast. Cross-sectional analysis involved 793 healthy pregnant women (35.3 ± 5.0 years) participating in ECLIPSES, a multicenter randomized trial. Socio-demographic, obstetric, anthropometric, lifestyle, dietary variables and blood draw was collected in the first trimester. Vitamin D deficiency was identified in 50.2% and insufficiency in 30.3% of pregnant women. The mean vitamin D level in the overall sample was 33.9 nmol/L (SD, 17.0). Multivariable logistic regression analysis applying AIC-based backward selection identified excess weight during the 1st trimester (BMI ≥ 25 kg/m²) (OR = 1.950, 95% CI = 1.409, 2.699), Arab ethnic group/dark skin colour (OR = 4.005, 95% CI = 2.488, 6.447), winter/spring (OR = 4.319, 95% CI = 3.112, 5.994), and consumption of milk (OR = 0.754, 95% CI = 0.572, 0.993) and yogurt (OR = 0.635, 95% CI = 0.436, 0.922) as independent risk factors for vitamin D deficiency. All of these factors (except yogurt consumption) and physical activity were independently associated with vitamin D deficiency/insufficiency risk in the final multivariable model (all p < 0.05). All these factors and social class were the most important determinants of circulating 25(OH)D concentrations. Our results confirm a high prevalence of vitamin D deficiency and insufficiency among pregnant women from the eastern Mediterranean coast.

Regimens of vitamin D supplementation for women during pregnancy

BACKGROUND

Vitamin D deficiency during pregnancy increases the risk of pre-eclampsia, gestational diabetes, preterm birth, and low birthweight. In a previous Cochrane Review we found that supplementing pregnant women with vitamin D alone compared to no vitamin D supplementation may reduce the risk of pre-eclampsia, gestational diabetes, and low birthweight and may increase the risk of preterm births if it is combined with calcium. However the effects of different vitamin D regimens are not yet clear.

OBJECTIVES

To assess the effects and safety of different regimens of vitamin D supplementation alone or in combination with calcium or other vitamins, minerals or nutrients during pregnancy, specifically doses of 601 international units per day (IU/d) or more versus 600 IU/d or less; and 4000 IU/d or more versus 3999 IU/d or less.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (12 July 2018), and the reference lists of retrieved studies.

SELECTION CRITERIA

Randomised trials evaluating the effect of different vitamin D regimens (dose, frequency, duration, and time of commencement of supplementation during pregnancy), alone or in combination with other nutrients on pregnancy and neonatal health outcomes. We only included trials that compared 601 IU/d or more versus 600 IU/d or less and 4000 IU/d or more versus 3999 IU/d or less. We did not include in the analysis groups that received no vitamin D, as that comparison is assessed in another Cochrane Review.

DATA COLLECTION AND ANALYSIS

Two review authors independently: i) assessed the eligibility of studies against the inclusion criteria; ii) extracted data from included studies, and iii) assessed the risk of bias of the included studies. Our primary maternal outcomes were: pre-eclampsia, gestational diabetes, and any adverse effects; our primary infant outcomes were preterm birth and low birthweight. Data were checked for accuracy. The certainty of the evidence was assessed using the GRADE approach.

MAIN RESULTS

In this review, we included data from 30 trials involving 7289 women. We excluded 11 trials, identified 16 ongoing/unpublished trials and two trials are awaiting classification. Overall risk of bias for the trials was mixed.Comparison 1. 601 IU/d or more versus 600 IU/d or less of vitamin D alone or with any other nutrient (19 trials; 5214 participants)Supplementation with 601 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of pre-eclampsia (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.65 to 1.42); 5 trials; 1553 participants,low-certainty evidence), may reduce the risk of gestational diabetes (RR 0.54, 95% CI 0.34 to 0.86; 5 trials; 1846 participants; moderate-certainty evidence), may make little or no difference to the risk of preterm birth (RR 1.25, 95% CI 0.92 to 1.69; 4 trials; 2294 participants; low-certainty evidence); and may make little or no difference to the risk of low birthweight (RR 0.90, 95% CI 0.66 to 1.24; 4 trials; 1550 participants; very low-certainty evidence) compared to women receiving 600 IU/d or less.Comparison 2. 4000 IU or more versus 3999 IU or less of vitamin D alone (15 trials; 4763 participants)Supplementation with 4000 IU/d or more of vitamin D during pregnancy may make little or no difference to the risk of: pre-eclampsia (RR 0.87, 95% CI 0.62 to 1.22; 4 trials, 1903 participants, low-certainty evidence); gestational diabetes (RR 0.89, 95% CI 0.56 to 1.42; 5 trials, 2276 participants; low-certainty evidence); preterm birth (RR 0.85, 95% CI 0.64 to 1.12; 6 trials, 2948 participants, low-certainty evidence); and low birthweight (RR 0.92, 95% CI 0.49 to 1.70; 2 trials; 1099 participants; low-certainty evidence) compared to women receiving 3999 IU/d or less.Adverse events (such as hypercalcaemia, hypocalcaemia, hypercalciuria, and hypovitaminosis D) were reported differently in most trials; however, in general, there was little to no side effects reported or similar cases between groups.

AUTHORS' CONCLUSIONS

Supplementing pregnant women with more than the current vitamin D recommendation may reduce the risk of gestational diabetes; however, it may make little or no difference to the risk of pre-eclampsia, preterm birth and low birthweight. Supplementing pregnant women with more than the current upper limit for vitamin D seems not to increase the risk of the outcomes evaluated. In general, the GRADE was considered low certainty for most of the primary outcomes due to serious risk of bias and imprecision of results. With respect to safety, it appears that vitamin D supplementation is a safe intervention during pregnancy, although the parameters used to determine this were either not reported or not consistent between trials. Future trials should be consistent in their reports of adverse events. There are 16 ongoing trials that when published, will increase the body of knowledge.

The relationship between maternal vitamin D status during third trimester of pregnancy and maternal and neonatal outcomes: A longitudinal study

Background

Vitamin D deficiency is a common nutritional concern and leads to several problems among some population groups.

Objective

The aim of the current study was to evaluate the relationship between maternal vitamin D status and gestational weight gain, maternal biochemical parameters, mode of delivery, and infants' growth indices at birth.

Materials and Methods

A longitudinal study between March and June 2017 was carried on 82 mothers in Ahvaz. Blood samples of each mother were obtained at the mean of the third trimester to assay lipid indices (total cholesterol, triglycerides, low-density lipoprotein, and high-density lipoprotein cholesterol), fasting blood sugar, and 25-hydroxy vitamin D. Anthropometric assessment of newborns was recorded from neonatal health card at birth.

Results

Mean maternal 25-hydroxy vitamin D level was 22.52 nmol/L; 7.33% of mothers had vitamin D deficiency, 76.6% had vitamin D insufficiency, and 15.9% were normal. The mean neonate birth weight, length, and head circumference of mothers who were on the third tercile of 25-hydroxy vitamin D serum level was significantly higher than those in the first tercile (p < 0.001, p = 0.004 and p < 0.001, respectively). Maternal vitamin D serum level had an adverse relationship with fasting blood sugar.

Conclusion

Low levels of serum vitamin D may cause adverse pregnancy outcomes and delivery of infants with insufficient growth at birth.

Vitamin D deficiency during pregnancy and its associated factors among third trimester Malaysian pregnant women

Background

Despite perennial sunshine, vitamin D deficiency is prevalent among Malaysians especially pregnant women. This study determines the vitamin D status and its associated factors among third trimester pregnant women attending government health clinics in Selangor and Kuala Lumpur, Malaysia.

Methods

Information on socio-demographic characteristics, obstetrical history, and sun exposure were obtained through face-to-face interviews. Vitamin D intake was assessed using a semi-quantitative food frequency questionnaire (FFQ). Serum 25-hydroxyvitamin D concentration was measured and classified as deficient (< 30 nmol/L), insufficient (30–50 nmol/L), and sufficient (≥ 50 nmol/L).

Results

Of the 535 pregnant women recruited, 42.6% were vitamin D deficient. They consumed an average of 8.7 ± 6.7 μg of vitamin D daily. A total of 80.4% of the vitamin D were obtained from the food sources, while 19.6% were from dietary supplements. Fish and fish products showed the highest contribution to vitamin D intake (35.8%). The multivariable generalized linear mixed models, with clinic as a random effect, indicates that higher intake of vitamin D is associated with lower odds of vitamin D deficiency among pregnant women (OR = 0.96; 95% CI = 0.93–0.99). The odds of having vitamin D deficiency was reduced by 87% in non-Malays (OR = 0.14; 95% CI = 0.05–0.41) compared to Malays. No associations were found between age, educational level, monthly household income, work status, gravidity, parity, pre-pregnancy body mass index, total hours of sun exposure, total percentage of body surface area, and sun exposure index per day with vitamin D deficiency.

Conclusion

Vitamin D deficiency is prevalent among Malaysian pregnant women. Considering the possible adverse obstetric and fetal outcomes of vitamin D deficiency during pregnancy, future nutrition education should emphasise on vitamin D-fortified foods consumption among pregnant women by taking into consideration ethnic differences.

High frequency of vitamin D deficiency in current pregnant Japanese women associated with UV avoidance and hypo-vitamin D diet

BACKGROUND

As a consequence of indoor occupations and reduced exposure to sunlight, concerns have been raised that vitamin D deficiency is widespread in developed countries. Vitamin D is known to be associated with increased risks of morbidity and mortality in various diseases.

OBJECTIVE

To investigate the serum vitamin D status and its relation with life-style factors in pregnant Japanese women.

METHODS

Among a cohort for 3,327 pregnant women who participated in an the adjunct study of the Japan Environment and Children's Study during 2011-2013, in which data were obtained on various life-style factors, including both dietary intake of vitamin D and frequency of UV exposure, this study consisted of 1,592 pregnant women, from whom 2,030 serum samples were drawn in Jan, Apr, Jul, and Oct, and the association between serum 25(OH)D level and life-style factors were analyzed using linear mixed models.

RESULTS

Serum 25(OH)D levels were less than 20ng/mL in 1,486 of 2,030 samples (73.2%). There was an obvious seasonal change, with serum 25(OH)D levels of less than 20 ng/mL in 89.8% and 47.8% of samples in spring (April) and autumn (October), respectively. Both the frequency spent under sunlight and dietary intake of vitamin D were significantly associated with serum 25(OH)D level. An increase in sunlight exposure of more than 15 min for 1 to 2 days per week in non-winter, or dietary intake of 2 μg/day of vitamin D resulted in an elevation of 1 ng/mL in serum 25(OH)D levels.

CONCLUSION

These findings indicate that vitamin D deficiency is very severe in Japanese pregnant women, especially those rarely exposed to sunlight. The benefits of UV rays should also be informed of when its risk is alerted, and clinicians should propose the adequate UV exposure level.

Hypovitaminosis D in pregnancy: Is it a public health issue?

Abstract Objectives: to measure the prevalence of hypovitaminosis D in healthy pregnant women and to analyze the association among some variables and the levels of vitamin D. Methods: an analytical cross-sectional study. 174 healthy pregnant women were selected from four basic health units in São Luís, Brazil, from January to February 2017. The participants answered a questionnaire about sociodemographic and obstetric data. A blood sample was collected to evaluate the plasmatic level of vitamin D. The association between independent variables and the outcome was evaluated by using the Student’s t-test and Chisquare test. Results: the mean of vitamin D concentration was 24.9±6.6ng/ml. Forty women (23.0%) presented vitamin D sufficiency, 93 (53.4%) insufficient, and 41 (23.6%) with deficiency. There was a difference in the vitamin D concentration between evangelical (23.1 ng/ml) and non-evangelical (25.5 ng/ml) (p=0.02) and between primigravida (23.8 ng/ml) and non-primigravida (25.7 ng/ml) (p=0.03). There was a difference in the hypovitaminosis D between adolescents (89.7%) and non-adolescents (72.6%) (p=0.02) and between primigravida (85.0%) and non-primigravida (69.2%) (p=0.01). Low monthly income per capita was associated with a higher frequency of vitamin D sufficiency. Conclusions: Due to the impact of inadequate levels of vitamin D in pregnant women and their babies’ health, even in an equatorial city, hypovitaminosis D in pregnant women is an important public health issue.

Disparities in the timing and measurement methods to assess vitamin D status during pregnancy: A Narrative Review

Studies that examined associations between low circulating 25-hydroxyvitamin D (25(OH)D) and adverse pregnancy outcomes used various designs, assay methods and time points for measurement of 25(OH)D concentrations, which creates some confusion in the current literature. We aimed to investigate the variability in the timing and measurement methods used to evaluate vitamin D status during pregnancy. Analysis of 198 studies published between 1976 and 2017 showed an important variability in the choice of 1) threshold values for 25(OH)D insufficiency or deficiency, 2) 25(OH)D measurement methods, and 3) trimester in which 25(OH)D concentrations were measured. Blood samples were taken once during pregnancy in a large majority of studies, which may not be representative of vitamin D status throughout pregnancy. Most studies reported adjustment for confounding factors including season of blood sampling, but very few studies used the 25(OH)D gold standard assay, the LC-MS/MS. Prospective studies assessing maternal 25(OH)D concentrations 1) by standardized and validated methods, 2) at various time points during pregnancy, and 3) after considering potential confounding factors, are needed.

Longitudinal association of 25-hydroxyvitamin D with adipokines and markers of glucose metabolism among Brazilian pregnant women

This study aimed to evaluate the longitudinal association of vitamin D status with glycaemia, insulin, homoeostatic model assessment of insulin resistance, adiponectin and leptin. A prospective cohort with 181 healthy, pregnant Brazilian women was followed at the 5th–13th, 20th–26th and 30th–36th gestational weeks. In this cohort, 25-hydroxyvitamin D (25(OH)D) plasma concentrations were analysed using liquid chromatography–tandem MS. Vitamin D status was categorised as sufficient or insufficient using the Endocrine Society Practice Guidelines (≥75/<75 nmol/l) and the Institute of Medicine (≥50/<50 nmol/l) thresholds. Linear mixed-effect regression models were employed to evaluate the association between vitamin D status and each outcome, considering interaction terms between vitamin D status and gestational age (P<0·1). At baseline, 70·7 % of pregnant women had 25(OH)D levels <75 nmol/l and 16 % had levels <50 nmol/l. Women with sufficient vitamin D status at baseline, using both thresholds, presented lower glycaemia than those with insufficient 25(OH)D. Pregnant women with 25(OH)D concentrations <75 nmol/l showed lower insulin (β=−0·12; 95 % CI −0·251, 0·009;P=0·069) and adiponectin (β=−0·070; 95 % CI −0·150, 0·010;P=0·085) concentrations throughout pregnancy than those with 25(OH)D levels ≥75 nmol/l. Pregnant women with 25(OH)D <50 nmol/l at baseline presented significantly higher leptin concentrations than those with 25(OH)D levels ≥50 nmol/l (β=−0·253; 95 % CI −0·044, 0·550;P=0·095). The baseline status of vitamin D influences the biomarkers involved in glucose metabolism. Vitamin D-sufficient women at baseline had higher increases in insulin and adiponectin changes throughout gestation than those who were insufficient.

Prevalence of vitamin D deficiency in cord blood of newborns and the association with maternal vitamin D status

Vitamin D deficiency is common in Southeast Asia but there are limited data in pregnant women and neonates. This study aimed to determine the prevalence of vitamin D deficiency in cord blood of newborns and the association with maternal vitamin D status. A total of 94 pregnant women and their neonates were included. Clinical data and venous maternal blood for calcium, phosphate, albumin, alkaline phosphatase, magnesium, intact parathyroid hormone (iPTH), and vitamin D (25OHD) were obtained on the day of labor. Cord blood was collected following delivery to evaluate vitamin D status of newborns. Mean serum maternal and cord blood 25OHD levels were 25.42 ± 8.07 and 14.85 ± 5.13 ng/mL. The prevalence of vitamin D deficiency (25OHD < 12 ng/mL) and insufficiency (25OHD 12-20 ng/mL) in cord blood of newborns were 20.2 and 69.1%, respectively. There was a significant correlation between maternal and cord blood vitamin D levels (r = 0.86; P < 0.001). The factors associated with cord blood vitamin D deficiency were low maternal 25OHD level and no vitamin D supplement during pregnancy.

CONCLUSION

There is a high prevalence of vitamin D deficiency among Thai neonates. Adequate prenatal vitamin D supplementation should be implemented as routine antenatal care. What is Known: • Vitamin D deficiency is prevalent in Southeast Asia. • There are widespread vitamin D deficiency among Thai populations including pregnant women. What is New: • There is a high prevalence of vitamin D deficiency among Thai neonates. • The factors associated with cord blood vitamin D deficiency are low maternal vitamin D level and no vitamin D supplement during pregnancy.

Global Overview of Vitamin D Status

Vitamin D deficiency occurs all over the world, mainly in the Middle East, China, Mongolia, and India. This article focuses on the vitamin D status in adults. Risk groups include older persons, pregnant women, and non-Western immigrants. Adequate vitamin D status, defined as serum 25-hydroxyvitamin D greater than 50 nmol/L, is present in less than 50% of the world population, at least in winter. Preventative strategies, such as increasing fish consumption, fortification of foods, use of vitamin D supplements, and advice for moderate sunlight exposure, are warranted.

Lower maternal and fetal vitamin D status and higher placental and umbilical vitamin D receptor expression in preeclamptic pregnancies

OBJECTIVE

To explore associations between maternal and fetal vitamin D status in preeclamptic pregnancies.

METHODS

A case-control experiment was carried out with proportion ratio of 1:1 (controls: n = 60 vs cases: n = 60). Blood collection of both maternal and cord were performed before and during delivery, respectively, and 25(OH)D measurement was conducted. Difference analysis was performed according to returned data. Immunohistochemical analysis, together with semi-quantitative Western blot, was also performed to determine protein expression of vitamin D receptor in placenta and cord tissues of ESPE.

RESULTS

Mean ± SD values of maternal 25(OH)D in control and PE group were 38.06 ± 6.28 and 33.05 ± 4.10, respectively, and significant differences with P < 0.0001 were found between control and PE in both continuous and categorical variables, especially in ESPE subtype (32.96 ± 4.49). The deficiency category (< 30 nmol/L) showed increased odds of PE (OR, 2.83, 95% CI, 1.32-6.08) in both maternal 25(OH)D and cord 25(OH)D in multivariable logistic regression. Semi-quantitative analysis showed that expression of placenta VDR in the ESPE subgroup was significantly higher than that in control group with P < 0.001, while expression of umbilical vein VDR in ESPE subgroup was significantly higher than that in control group with P < 0.05.

CONCLUSIONS

The present study finds that lowest maternal and fetal vitamin D status in ESPE existed in the preeclampsia subsets. The VDR expression in placenta and fetus in ESPE were higher than that of normal pregnancy, which indicated that it might be related to placenta compensatory mechanism and is worthy of further research.

Inverse associations between cord vitamin D and attention deficit hyperactivity disorder symptoms: A child cohort study

OBJECTIVE

To examine the association between cord 25-hydroxyvitamin D₂₊₃ (25(OH)D) and attention deficit hyperactivity disorder symptoms in toddlers, using Child Behaviour Checklist for ages 1.5-5.

METHOD

In a population-based birth cohort, a Child Behaviour Checklist for ages 1.5-5 questionnaire was returned from parents of 1233 infants with mean age 2.7 (standard deviation 0.6) years. Adjusted associations between cord 25(OH)D and Child Behaviour Checklist-based attention deficit hyperactivity disorder problems were analysed by multiple regression. Results The median cord 25(OH)D was 44.1 (range: 1.5-127.1) nmol/L. Mean attention deficit hyperactivity disorder problem score was 2.7 (standard deviation 2.1). In adjusted analyses, cord 25(OH)D levels >25 nmol/L and >30 nmol/L were associated with lower attention deficit hyperactivity disorder scores compared to levels ⩽25 nmol/L ( p = 0.035) and ⩽30 nmol/L ( p = 0.043), respectively. The adjusted odds of scoring above the 90th percentile on the Child Behaviour Checklist-based attention deficit hyperactivity disorder problem scale decreased by 11% per 10 nmol/L increase in cord 25(OH)D.

CONCLUSION

An inverse association between cord 25(OH)D and attention deficit hyperactivity disorder symptoms in toddlers was found, suggesting a protective effect of prenatal vitamin D.

Changes in plasma concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D during pregnancy: a Brazilian cohort

PURPOSE

To characterize the physiological changes in 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)₂D] throughout pregnancy.

METHODS

Prospective cohort of 229 apparently healthy pregnant women followed at 5th-13th, 20th-26th, and 30th-36th gestational weeks. 25(OH)D and 1,25(OH)₂D concentrations were measured by LC-MS/MS. Statistical analyses included longitudinal linear mixed-effects models adjusted for parity, season, education, self-reported skin color, and pre-pregnancy BMI. Vitamin D status was defined based on 25(OH)D concentrations according to the Endocrine Society Practice Guideline and Institute of Medicine (IOM) for adults.

RESULTS

The prevalence of 25(OH)D <75 nmol/L was 70.4, 41.0, and 33.9%; the prevalence of 25(OH)D <50 nmol/L was 16.1, 11.2, and 10.2%; and the prevalence of 25(OH)D <30 nmol/L was 2, 0, and 0.6%, at the first, second, and third trimesters, respectively. Unadjusted analysis showed an increase in 25(OH)D (β = 0.869; 95% CI 0.723-1.014; P < 0.001) and 1,25(OH)₂D (β = 3.878; 95% CI 3.136-4.620; P < 0.001) throughout pregnancy. Multiple adjusted analyses showed that women who started the study in winter (P < 0.001), spring (P < 0.001), or autumn (P = 0.028) presented a longitudinal increase in 25(OH)D concentrations, while women that started during summer did not. Increase of 1,25(OH)₂D concentrations over time in women with insufficient vitamin D (50-75 nmol/L) at baseline was higher compared to women with sufficient vitamin D (≥75 nmol/L) (P = 0.006).

CONCLUSIONS

The prevalence of vitamin D inadequacy varied significantly according to the adopted criteria. There was a seasonal variation of 25(OH)D during pregnancy. The women with insufficient vitamin D status present greater longitudinal increases in the concentrations of 1,25(OH)₂D in comparison to women with sufficiency.

Vitamin D status and the prevalence of deficiency in lactating women from eight provinces and municipalities in China

BACKGROUND

Vitamin D deficiency has become prevalent worldwide in recent years. However, less evidence was available for lactating women.

OBJECTIVE

The purpose of the study was to understand vitamin D status and prevalence of deficiency in lactating women and associated risk factors for vitamin D deficiency from eight provinces and municipalities in China.

METHODS

Lactating women within 1-10 months postpartum were recruited in 2011-2013 from eight provinces and municipalities in China. Radioimmunoassay was used to measure serum 25-hydroxyvitamin D [25(OH)D] concentration. Standardized questionnaire was used to collect information on season, living site, ethnicity and socio-demographic characteristics.

RESULTS

Totally 2004 lactating women were recruited. The median (p25, p75) of 25(OH)D was 15.8 (10.5, 24.0) nmol/L. The prevalence of vitamin D deficiency was 85.3% as 25(OH)D <30nmol/L. Serum 25(OH)D levels of lactating women were significantly lower during October-January (14.0nmol/L) than during February-May (18.0nmol/L) (P<0.001), and were significantly higher in Dai ethnicity (22.5nmol/L) than in Hui ethnicity (Chinese Muslims) (9.0nmol/L) (P<0.001). For every 10,000 CNY annual income per capita increasing, serum 25(OH)D levels significantly increased 1.04 times (P<0.001). The odds of vitamin D deficiency in winter were 2.56 times higher than that in spring (OR 2.56, 95%CI: 1.91-3.43).

CONCLUSIONS

Vitamin D deficiency of lactating women was highly prevalent in the eight provinces and municipalities in China. It is urgent to study the strategy and intervention ways for improving vitamin D status of lactating women, especially for certain population groups during low sunlight exposure season.

Effect of tailored dietary guidance for pregnant women on nutritional status: A double-cohort study

This double cohort study aimed to evaluate the effect of tailored dietary guidance for pregnant women on dietary intake, nutritional status, and infant birth weight. Healthy pregnant women were recruited at an antenatal clinic during two phases over 2 years. The historical controls were analyzed a year prior to the intervention group. In both groups, data were collected at 19-26 gestational weeks (baseline) and at 34-37 gestational weeks (outcome measurement). The intervention included the following: (a) assessments of maternal dietary nutritional intake using the brief self-administered diet history questionnaire, (b) individual feedback based on the assessments of maternal nutritional status, (c) tailored guidance for a healthy diet, (d) original cooking recipes, and (e) goal sharing. Mann-Whitney U test was used to compare the outcome data between the groups. Of the 378 eligible women, 309 women had follow-up questionnaire data. Blood samples were obtained from 202 women. Despite a lack of improvement in reported dietary intake, plasma eicosapentaenoic acid (p = .002), docosahexaenoic acid (p < .001), arachidonic acid (p < .001), and dihomo-gamma-linolenic acid (p < .001) concentrations as well as maternal weight gain (p = .019) were significantly higher in the intervention group. However, serum folate (p = .031) concentration was significantly lower in the intervention group, and there were no significant differences between the groups in 25-hydroxy vitamin D levels, blood count, average birth weight, and rate of low birth weight infants. Assessment-based tailored guidance individualized to maternal dietary intake might partially contribute to improved nutrition in pregnant women.