key: cord-0957072-bajceqio
authors: Sinaci, Selcan; Ocal, Doga Fatma; Yucel Yetiskin, Didem Fatma; Uyan Hendem, Derya; Buyuk, Gul Nihal; Goncu Ayhan, Sule; Tanacan, Atakan; Ozgu-Erdinc, A. Seval; Moraloglu Tekin, Ozlem; Sahin, Dilek
title: Impact of vitamin D on the course of COVID-19 during pregnancy: A case control study
date: 2021-08-11
journal: J Steroid Biochem Mol Biol
DOI: 10.1016/j.jsbmb.2021.105964
sha: 0d021c43cd09a4069372c6069659f561dc94201d
doc_id: 957072
cord_uid: bajceqio

OBJECTIVE: We aimed to evaluate the vitamin D status of pregnant women with COVID-19, and the association between vitamin D level and severity of COVID-19. METHODS: In this case control study, 159 women with a single pregnancy and tested positive for SARS-CoV-2, and randomly selected 332 healthy pregnant women with similar gestational ages were included. COVID-19 patients were classified as mild, moderate, and severe. Vitamin D deficiency was defined as 25-hydroxycholecalciferol <20 ng/mL (50 nmol/L), and 25-OH D vitamin <10 ng/mL was defined as severe vitamin D deficiency, also 25-OH D vitamin level between 20-29 ng/mL (525-725 nmol/L) was defined as vitamin D insufficiency. RESULTS: Vitamin D levels of the pregnant women in the COVID-19 group (12.46) were lower than the control group (18.76). 25-OH D vitamin levels of those in the mild COVID-19 category (13.69) were significantly higher than those in the moderate/severe category (9.06). In terms of taking vitamin D supplementation, there was no statistically significant difference between the groups. However, it was observed that all of those who had severe COVID-19 were the patients who did not take vitamin D supplementation. CONCLUSION: The vitamin D levels are low in pregnant women with COVID-19. Also, there is a significant difference regarding to vitamin D level and COVID-19 severity in pregnant women. Maintenance of adequate vitamin D level can be useful as an approach for the prevention of an aggressive course of the inflammation induced by this novel coronavirus in pregnant women.

The novel Severe Acute Respiratory Syndrome-coronavirus-2 (SARS-CoV-2) originated in Wuhan, Hubei, China in December 2019 [1] . Since it was declared a pandemic by the World Health Organization on March 11, 2020, millions of people around the world have been affected [2, 3] .

Although COVID-19 is characterized by high infectivity, the majority of those affected are asymptomatic. While most of the cases show mild symptoms, severe illness develops only in less than 15% [4, 5] . Pregnant women with novel coronavirus 2019 (COVID- 19) and their newborns remain in the substantially unknown part of the issue. Comparing to nonpregnant women, pregnancy may worsen the course of COVID-19 infection. In the literature, it has been indicated that COVID-19 may cause an increase in obstetric complications such as preterm labor and fetal distress [6,7,8].

Vitamin D is a fat-soluble vitamin and steroid hormone produced on the skin with the effect of ultraviolet radiation and also can be obtained from exogenous food sources or dietary supplements. Maternal vitamin D deficiency is an important worldwide public health problem that may worsen pregnancy outcomes [9] . Vitamin D deficiency is common among pregnant women. In a recent study, the prevalence of vitamin D deficiency in pregnant women in our country was reported as 81.4-86%. [10, 11] . Vitamin D has various effects during pregnancy such as placental implantation, angiogenesis, immune function, oxidative stress, endothelial function, inflammatory response, and glucose homeostasis [12, 13] . A meta-analysis of observational studies has shown a positive association between low vitamin D levels and adverse pregnancy outcomes such as preeclampsia, gestational diabetes mellitus, preterm birth, and SGA (small-for-gestational age) [14].

Vitamin D supplementation has been shown to reduce the incidence of viral respiratory infections [15] [16] [17] . It is thought that vitamin D supplementation could be a useful method to reduce the risk of influenza and COVID-19 [15] [16] [17] [18] . The role of vitamin D in the response to COVID-19 is twofold. First, vitamin D increases the production of antimicrobial peptides in the respiratory epithelium and reduces viral replication rates, making viral infection and symptoms milder. Second, Vitamin D reduces the inflammatory response to SARS CoV-2 by increasing antiinflammatory cytokine concentrations and decreasing the concentrations of pro-inflammatory cytokines which increase lung damage [16] .

Recently, a range of studies reported that low vitamin D levels are associated with an increased risk of COVID-19 positivity [17, [19] [20] [21] . Additionally, many studies in the literature show a strong association between vitamin D deficiency and COVID-19 hospitalisation, severity and mortality [15, 17, [21] [22] [23] [24] . ARDS (acute respiratory distress syndrome) caused by COVID-19 and its damage to other organs is secondary to cytokine storm and related oxidative stress. Active hydroxyl forms of vitamin D are anti-inflammatory, inducing anti-oxidative responses and inducing innate immunity against infectious agents [24] [25] [26] . Lower vitamin D levels in winter are facilitating viral outbreaks, and vitamin D supplementation may reduce the incidence, severity, and risk of viral diseases [24] [25] [26] [27] . On the other hand, the association between the incidence of severe COVID-19 and 25-OH D vitamin level is controversial, as some studies do not show a benefit when it is administered in critical cases [15,28-33].

In our study, for the first time, we aimed to evaluate 25-OH D vitamin levels of pregnant women with and without COVID-19 infection, which is a sensitive group, and also whether the vitamin D level are associated with the severity of COVID-19.

This case control study was carried out between July-December 2020 at the Ministry of Health Ankara City Hospital, the main public maternity hospital which handles approxiametly 15.000 deliveries yearly and covers all surgical and medical disciplines.

159 women with a single pregnancy, from all trimesters and tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using quantitative RT PCR (qRT-PCR) from nasopharyngeal and oropharyngeal samples were included in the study. According to the Chinese management guideline for COVID-19 (version 6.0), patients were classified as mild, moderate, and severe [34]. Those who had maternal systemic diseases (diabetes, cardiovascular diseases, hypertensive diseases of pregnancy, asthma, thromboembolic disorders, inflammatory bowel diseases, autoimmune connective tissue diseases, other infectious diseases) and multifetal pregnancy were excluded. Randomly selected 332 singleton pregnant women with similar gestational ages were designed as the control group for the same period. The following information was recorded by the researchers: maternal age; gravidity; parity; the number of living children; previous miscarriages; pre-pregnancy body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters; BMI ≥30 was defined as obese); gestational age at diagnosis; minimum oxygen saturation; disease severity; maternal mortality; mode of delivery; obstetric and neonatal outcomes; taking vitamin D supplementation; and the following laboratory parameters at the time of admission: 25-OH D vitamin (ng/mL), D-dimer (mg/L), CRP, IL-6. According to the National Institute's prophylaxis recommendations for pregnant women, whether taking vitamin D supplementation was noted. Blood samples were taken from the antecubital vein and serum 25-OH D vitamin levels (which is the most reliable biomarker of functional vitamin D status) were measured using enzyme-linked immunosorbent assay (ELISA). 25hydroxycholecalciferol level <20ng/mL (50 nmol/L) was defined as vitamin D deficiency, <10ng/mL was defined as severe vitamin D deficiency, and 25-OH D vitamin level between 20-29ng/mL (525-725 nmol/L) was defined as vitamin D insufficiency, according to the Endocrine Society Guidelines [35].

SPSS for Microsoft Windows 24.0 (SPSS Inc., Armonk, NY, USA) was used for statistical analyses. Frequency tables and descriptive statistics were used in the interpretation of the findings.

The relationship between two qualitative variables, the expected value levels were analyzed by the Fisher-Exact and Pearson-χ 2 test. The Mann-Whitney U test (Z-table value) was used to compare the measurement values of two independent groups. p<0.05 indicates a statistically significant correlation.

The patients of COVID-19 and the normal pregnancy group did not differ in terms of maternal age, gestational week, gravidity, parity, pre-pregnancy BMI, and vitamin D supplementation, as seen in Table 1 . A statistically significant difference was found between the groups in terms of Apgar 5 th minute value. Apgar 5 th minutes scores were significantly lower in the COVID-19 group than the control group (p<0.05). As presented in Table 1 , the Vitamin D levels of the patients in the COVID-19 group (12.46) were statistically significant lower than the control group (18.76) (p=0.004). 11 newborns were admitted to NICU in COVID-19 group, and indication was low birth weight in 8 cases, transient tachypnea of newborn in 3 cases. The mothers of the 7 newborns were in mild, 3 were in moderate, 1 was in severe COVID-19 category. One fetus died in utero at 25 gestational weeks, whose mother was in mild COVID-19 category and on the 4 th day of the SARS-CoV-2 PCR positivity. Also, nasopharyngeal PCR of the newborn was negative for SARS-CoV-2. As presented in Table 2 , there was a significant difference in 25-OH D vitamin levels between COVID-19 and control group (p=0.000). While the majority of the patients in the control group had vitamin D insufficiency and deficiency, severe 25-OH D vitamin deficiency had the highest rate in the COVID-19 patients.

J o u r n a l P r e -p r o o f As presented in Table 3 . five mothers died in severe COVID-19 category. While one mother was at 12 gestational week, four of them were in mid-late third trimester of the pregnancy. 25-OH D vitamin level of those were ranging between 4.5 and 12.

J o u r n a l P r e -p r o o f The distribution of vitamin D levels according to COVID-19 categories was given in Table 4 . There was a statistically significant relationship between groups in terms of COVID-19 severity and 25-OH D vitamin level (p<0.05). Although 25-OH D vitamin levels were low in both groups, 25-OH D vitamin levels of those in the mild COVID-19 group (13.69) were significantly higher than those in the moderate or severe COVID-19 group (9.06) (p<0.05). There was a significant relationship between groups in terms of 25-OH D vitamin deficiency and COVID-19 severity (p=0.000). In both mild and moderate+severe COVID-19 groups, the majority of the patients had severe 25-OH D vitamin deficiency. There was no statistically significant relationship between vitamin D supplementation and COVID-19 severity (p>0.05). However, it was observed that all of those who had severe COVID-19 were the patients who did not take vitamin D supplementation. In those taking vitamin D supplementation, the mild COVID-19 rate was 77.8%; while moderate and severe was 22.2%, as seen in Table 6 .

There are several reports from different countries mentioning that vitamin D deficiency is associated with the incidence and severity of COVID-19. The ongoing debate is focusing on the idea that vitamin D supplementation may reduce the viral infection risk and the majority of the risk groups for severe COVID-19 tend to have vitamin D deficiency.

It is known that SARS-CoV-2 causes an excessively increased production of proinflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), interleukin-12 (IL-12), and especially interleukin-6 [IL-6] [36]. Hyperactivation of immune cells results in hypercytokinemia with excessive innate immune response and infiltration of inflammatory cytokines in lung cells [37, 38] . Extensive tissue damage with dysfunctional coagulation results in acute lung injury called acute respiratory distress syndrome (ARDS) related to COVID-19. An unrestricted immune reaction in the host leads to the situation called cytokine storm which is associated with the severity of COVID-19.

Apart from its effects on bone health and calcium-phosphor metabolism, vitamin D also plays an essential role in the immune system. T regulatory lymphocytes (Tregs) generally provide a basic defense against viral infection and prevent uncontrolled inflammation which has been reported to be low in COVID-19 patients, furthermore significantly lower in severe cases [39] . It suggests that supplementation of vitamin D, which is effective in raising Tregs levels, may be beneficial in reducing the severity of COVID-19 [40] . Vitamin D inhibits T cell proliferation and activation and acts on most immune system cells such as macrophages, neutrophils, and dendritic cells. Also, vitamin D has a regulatory role on the immune system, downregulating the production of proinflammatory cytokines and increasing the production of anti-inflammatory cytokines [41, 42] . In some recent studies, it was reported that vitamin D deficiency is related to increased levels of proinflammatory cytokines such as TNF-α and IL-6 and it was claimed that adequate levels of vitamin D may reduce the incidence of cytokine storm, which can occur in severe COVID-19 cases [42] [43] [44] . Vitamin D stabilizes the immune response supporting the innate immune system that provides an anti-inflammatory response [42, 43] . Due to its effects on the immune system, vitamin D may reduce the course of severe COVID-19 [15, 17, [21] [22] [23] [24] .

In the literature, the majority of the studies reported a significant association between vitamin D deficiency and COVID-19 incidence, while some others claimed the opposite by showing that there is no such association [15, [18] [19] [20] [21] [22] [23] [24] 43, 44] . In this study, we observed a prominent association between vitamin D deficiency and the incidence of COVID-19 in pregnant women. Additionally, 25-OH D vitamin levels were low (<20 ng/mL) on both COVID-19 (12.46) and control (18.76) groups. Considering the fact that vitamin D deficiency is common among pregnant women, we think it is not surprising that 25-OH vitamin D levels were also low in healthy pregnant women in control group Through several mechanisms, vitamin D is likely to reduce acute respiratory tract infection risk [15] [16] [17] . For prevention of the infection, 25-OH D vitamin level is recommended to be between 40-60 ng/ml [24] . A meta-analysis of 15 randomized controlled trials that investigated the effectiveness of vitamin D supplementation in reducing the risk of developing respiratory tract infections indicated no significant risk reduction among healthy individuals [45] . However, supplementation is required especially in the case of vitamin D deficiency. In 2011, the Endocrine Society recommended 1000-4000 IU/day (up to 10.000 IU/day particularly for obese individuals) vitamin D supplementation to reach serum 25-OH D vitamin levels above 30 ng/mL, especially in winter [35] . The upper limit of supplementation for pregnant women is reported to be 5000 IU/day in the literature [46]. In our study population, the majority of the patients were not on vitamin D supplementation. Also, the patients taking vitamin D supplements were using it at the prophylaxis dose. Although our results showed no statistically significant correlation between vitamin D supplementation and COVID-19 severity, similar to the literature, we observed that none of the severe cases were using vitamin D supplementation [15, 19, 21] .

If a good nutritional status and vitamin D supplementation provided in vulnerable populations such as pregnancy, it may be conceivable that the spread of COVID-19 will decrease due to the immuneenhancing and anti-inflammatory effects of vitamin D [47] . Therefore, effective prophylaxis programs for vitamin D deficiency are essential to prevent vitamin D deficiency and its obstetric outcomes in pregnant women, especially in the winter season [48] . However, further research and clinical trials are needed on both the therapeutic and preventive roles of vitamin D supplementation in pregnant women with COVID-19 infection. Based on the available literature, a plausible presumption is that the pre-infectious level of vitamin D in pregnant women might be of particular importance for the resistance to the progressing course of COVID-19.

A potential limitation of this study is the relatively low number of moderate and severe COVID-19 cases, which was probably related to the course of COVID-19 being mild in most of the pregnant patients. However, although the numbers were low since the population size is high, the small numbers were considered sufficient to present early results about COVID-19 and its relationship with vitamin D level during pregnancy.

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