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 Table of Contents  
Year : 2022  |  Volume : 1  |  Issue : 2  |  Page : 83-89

Vitamin D status and sociodemographic profile of pregnant Nigerian Igbo women

1 Department of Obstetrics and Gynecology, Nnamdi Azikiwe University and Teaching Hospital (NAUTH), Nnewi, Nigeria; Centre for Health and Allied Legal and Demographical Development Research and Training (CHALADDRAT), Nnamdi Azikiwe University, Awka, Nigeria
2 Department of Chemical Pathology, Nnamdi Azikiwe University and Teaching Hospital, Nnewi, Nigeria
3 Department of Community Medicine, Nnamdi Azikiwe University and Teaching Hospital, Nnewi, Nigeria
4 Department of Obstetrics and Gynecology, Nnamdi Azikiwe University and Teaching Hospital (NAUTH), Nnewi, Nigeria
5 Centre for Health and Allied Legal and Demographical Development Research and Training (CHALADDRAT), Nnamdi Azikiwe University, Awka, Nigeria; Department of Human Biochemistry, Nnamdi Azikiwe University, Nnewi, Nigeria, Nigeria

Date of Submission06-Jul-2022
Date of Acceptance30-Sep-2022
Date of Web Publication27-Dec-2022

Correspondence Address:
Joseph I B -D Adinma
Department of Obstetrics and Gynecology, Nnamdi Azikiwe University and Teaching Hospital (NAUTH), Nnewi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jnam.jnam_18_22

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Background: Vitamin D deficiency (VDD) in pregnancy is of major public health concern because of the effect it may have on maternal and fetal outcomes. Some of these effects include gestational diabetes mellitus, preeclampsia, infections, increased rate of cesarean sections, fetal growth restrictions, and poor fetal and infant bone mineralization. Aims: The aim of this article is to determine the serum vitamin D levels of pregnant women and the influence of some sociodemographic factors on vitamin D status. Subjects and Methods: This prospective, cross-sectional study, involving 256 consecutive parturient Igbo women, was carried out at two locations in Anambra State of southeastern Nigeria. Ethical approval and appropriate participatory consent were elicited and obtained from the participants. Blood samples were taken from the women during labor. Serum obtained from each maternal blood sample was labeled, stored in a refrigerator at -80°C, and ultimately assayed for 25-hydroxyvitamin D3 using high performance liquid chromatography. A proforma eliciting the biosocial characteristics was also completed for each of the pregnant woman. Data analysis was performed using SPSS version 23. Serum vitamin D level of ≥32 ng/mL was reported as normal, whereas that of <32 ng/mL was reported as deficiency. Comparison of variables was carried out using the χ2 test and Student’s t-test with P-value less than 0.05 at 95% confidence interval, which was considered to be significant. Results: In this study, VDD occurred in 36 (14.1%) women. VDD occurred significantly higher among multiparous women (para 1–4), P = 0.011. All 36 (100%) women with VDD occurred at term gestational age (37–42 weeks). VDD was more prevalent in dark complexion compared with others. Women with indoor work location had higher prevalence of VDD than those of outdoor, and all the women with VDD were of urban domicile. Conclusion: VDD is low in this study and is significantly influenced by parity, gestational age, complexion, location of work place, and place of domicile. It is recommended that pre- and early pregnancy administration of vitamin D supplements be individualized on the basis of certain biosocial factors: multiparity, term gestational age, dark complexion, indoor work location, and urban domicile.

Keywords: Nigerian Igbo women, sociodemographic profile, vitamin D status

How to cite this article:
Adinma JI, Ahaneku JE, Adinma ED, Ugboaja JO, Egeonu RO, Adinma-Obiajulu ND, Edet MM. Vitamin D status and sociodemographic profile of pregnant Nigerian Igbo women. J Niger Acad Med 2022;1:83-9

How to cite this URL:
Adinma JI, Ahaneku JE, Adinma ED, Ugboaja JO, Egeonu RO, Adinma-Obiajulu ND, Edet MM. Vitamin D status and sociodemographic profile of pregnant Nigerian Igbo women. J Niger Acad Med [serial online] 2022 [cited 2023 Jun 9];1:83-9. Available from: http://www.jnam.com/text.asp?2022/1/2/83/365600

  Introduction Top

Vitamin D deficiency (VDD) in pregnancy is of global public health concern because of the role vitamin D plays in optimizing outcomes for the mother and the fetus following pregnancy. Vitamin D along with parathyroid hormones is an essential ingredient to calcium homeostasis and bone mineralization.[1] It plays a significant role in the absorption of calcium from the digestive tract, thereby making it available in sufficient amount for the development of fetal bones[2] and for the enhancement of uterine contractility and prevention of uterine hypotonia and postpartum hemorrhage.[3],[4] Several reports have highlighted the relationship between maternal VDD and various conditions associated with pregnancy that may affect its ultimate outcomes such as gestational diabetes, pregnancy-induced hypertension/preeclampsia, bacterial vaginosis,[5],[6] cesarean section, preterm labor, and low birth weight.[7],[8],[9],[10] Up to 90% of vitamin D in humans is obtained from direct synthesis from sunlight involving a non-enzymatic conversion of 7-dehydroxycholesterol to pre-vitamin D3, which is ultimately converted to vitamin D3.[11] Ten percent of vitamin D is obtained from intake of diets and supplements and synthesized as vitamin D2.[2],[11] Vitamins D2 and D3 are thereafter successively acted upon by α-hydroxylase enzyme in the liver and kidney to produce the predominant circulating forms: 25-hydroxyvitamin D, employed in the determination of serum levels of vitamin D, and 1,25-dihydroxyvitamin D, the biologically active form of the vitamin.[12] Although 1α-hydroxylase enzyme is readily available in the kidney, it is also present in small amount in other body tissues such as endothelial and vascular smooth muscles.[13] It is worthy of note that in up to 30 different tissues including pancreas, myocardium, and lymphocytes, vitamin D receptors have been found.[14]

The prevalence rate of VDD has shown a wide variation between different countries in the world.[15],[16],[17],[18],[19] Even in some tropical countries with abundant sunshine, very high values have been reported, for example, a prevalence rate has been reported among pregnant women in Indonesia to be as high as 95%.[2]

In sub-Saharan Africa with a homogeneous black population, although there is adequate sunlight, the skin is thickly pigmented acting as a sunscreen to prohibit cutaneous vitamin D synthesis. VDD should therefore be expected to be high. Paradoxically, this is not always so, for example, VDD prevalence as low as 4.8% has been reported in a Nigerian study.[20] This implies that several factors other than cutaneous vitamin D synthesis may account for the prevalence of VDD in any country. It has been reported that cultural factors and personal lifestyle, to a considerable extent, can determine the availability of vitamin D in people because of their influence on exposure to sunshine. This study has been conducted among the Igbo-speaking pregnant women of southeastern Nigeria to determine the influence, if any, of certain sociodemographic factors on their vitamin D status (whether deficient or normal). The study may inform the development of policy guidelines on the necessity or not for a rational administration of vitamin D supplements for pregnant women in the subregion.

Study background

Anambra State, the location for this study, is one of the five states of southeastern Nigeria and harbors a homogenous Igbo-speaking ethnic group in Nigeria. The Igbos comprise one of the three major ethnic groups in Nigeria, and the others being the Yorubas of the West and the Hausas of the North. These major ethnic groups have religious and cultural peculiarities that are different from one another. The state has a population of approximately 5 million people who are mostly traders and of Christian religious denomination, with a few animist adherents. The health facilities for this study—Nnamdi Azikiwe University Teaching Hospital (NAUTH) and Holy Rosary Maternity Hospital (Waterside), Onitsha—are, respectively, tertiary and secondary health facilities with patient catchment that cuts across no fewer than six states of Nigeria and an antenatal patient mix that cuts across various socio-economic classes from both rural and urban areas.

  Subjects and Methods Top

A total of 256 consecutive parturient women drawn from the two study locations were involved in this cross-sectional study. Ethical approval was obtained from the Ethics Committee of the two health facilities, and the study was conducted on consenting pregnant parturient women after prior explanation of the process. Various individuals involved in the conduct of the study—the investigators, Heads of Department of Obstetrics and Gynecology at the study facilities, resident doctors, nurses, and pathologists—had preliminary meetings and appropriate trainings to ensure a smooth and successful conduct of the exercise.

Blood sample was collected from each parturient woman during labor. Serum obtained from the sample was labeled and stored at -80°C. The assay of the stored serum for vitamin D3 was conducted using high performance liquid chromatography (HPLC). The serum vitamin D level of ≥32 ng/mL was regarded as normal, whereas that below (<32 ng/mL) was regarded as deficiency. In addition, a proforma was completed for each of the parturient women. It elicited information with respect to the biocharacteristics: maternal age, parity, gestational age, and the complexion of the women, that is, fair-skinned, light-skinned, or dark. Information was also obtained in respect of her social characteristics: social class (SC) (1–5), place of domicile (rural or urban), and the location of her work place—indoor or outdoor. The SC of the women was derived from Olusanya classification, which involves the use of the educational level of the woman and her husband’s occupation.[21] Data obtained from the proforma and study blood sample were coded and keyed into the computer for analysis. Data analysis was performed using SPSS version 23. The variables in the proforma were assessed for vitamin D status—deficiency or normal—and presented in tables or charts. Comparison of variables was carried out using the χ2 test and Student’s t-test where necessary, with P-values of less than 0.05 at 95% confidence interval considered to be statistically significant.

  Results Top

[Table 1] shows the distribution by vitamin D status of the parturient women. Normal vitamin D (NVD) level occurred in 220 (85.9%) women, whereas VDD occurred in 36 (14.1%) pregnant women. The mean vitamin D level for women with VDD is 29.49 ± 1.26 ng/mL, whereas that for women with normal levels of vitamin D is 48.04 ± 10.23 ng/mL. The difference was statistically significant (P = 0.000).
Table 1: Distribution by normal and deficient levels of vitamin D of the pregnant women

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[Table 2] shows the distribution by biocharacteristics (maternal age, gestational age, and parity) for vitamin D status of the pregnant women. Deficient levels of serum vitamin D occurred mostly among the women aged 30–34 years (VDD = 16, 44.4%; NVD = 73, 33.2%) when compared with other age ranges. Although this was not statistically significant, VDD increased with increasing parity. Deficient levels of vitamin D occurred more significantly in the grand multipara (para 5 and above) (VDD = 4, 1.1%; NVD = 4, 1.8%), compared with the other parity groups (i.e., para 0 and para 1–4) (P = 0.011). All 36 (100%) women with VDD occurred at term (37–42 weeks) in contrast to 156 (70.9%) of normal occurring at term (P = 0.006).
Table 2: Distribution by biocharacteristics (maternal age, gestational age, and parity) for vitamin D status of the pregnant women

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[Figure 1] shows the distribution by vitamin D status of the pregnant women for complexion. VDD occurred significantly among the dark complexion parturient women [32 (88.9%)], compared with the light-skinned 4 (11.1%) and the fair-skinned 0 (0.0%) (P = 0.000).
Figure 1: Distribution by vitamin D status of the pregnant women for complexion

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The distribution by the SC of the parturient women is shown in [Table 3]: VDD increased with decreasing SC up to social class 4, although this trend was not statistically significant (P = 0.111).
Table 3: Distribution by the social class of the parturient women for their vitamin D status: deficiency and normal

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[Table 4] shows the distribution by the location of workplace and place of domicile of the pregnant women for their vitamin D status. Deficient levels of vitamin D significantly occurred among the pregnant women with indoor occupation [28 (77.8%)], compared with those whose occupation was outdoor [8 (22.2%)] (P = 0.004). All the women (100%) with low levels of vitamin D were of urban domicile, whereas all the women residing in the rural area had NVD levels [34 (15.5%), P = 0.029].
Table 4: Distribution by the location of work place and place of domicile for vitamin D status of the pregnant women

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  Discussion Top

Our previous study on vitamin D conducted among pregnant women in labor showed a VDD prevalence rate of 7.5%, much lower than the result from the present study (14.1%),[22] although the present study has been conducted among a greater population of pregnant women (256) drawn from two categories of health facilities, secondary and tertiary, in contrary to the previous study which was a basic pilot of 40 pregnant women conducted solely from a tertiary health facility. The variation in the prevalence of vitamin D from the two studies seems to corroborate global VDD prevalence figures that show great variations between countries and regions, ranging from as low as 4.8%[20] in a Nigerian study to as high as 95% in an Indonesian study.[2],[23] The literature is replete with numerous factors that have been found to significantly determine the prevalence of VDD and this includes sex, childhood/adolescent habit, occupation, exercise/other physical activities, nutritional factors, degree of exposure to sunlight, domicile in urban area, religion, and season of the year.[20],[23],[24],[25]

Pratumvinit et al.[26] in their study of 146 pregnant women in Thailand reported that VDD was more prevalent among women with lower pre-pregnant body mass index and winter season.[26]

This study has not shown any significant relationship between maternal age and vitamin D status. This is presumably due to the fact that the effect of exposure to sunshine is expected to occur evenly, irrespective of maternal age. This observation agrees with that of Karras et al.,[27] who found no relationship between vitamin D level and maternal age, but contrasts with that of Al-Daghri et al.,[28] who reported a higher prevalence of VDD among women of younger age group in Saudi Arabia.[28]

The influence of parity on VDD is evident from this study which demonstrates a significantly high prevalence of VDD among the multiparous women (para 1–4), compared with other parity groups. This observation differs from that of Owie and Afolabi,[20] Karras et al.,[27] and Andersen et al.,[29] whose reports are in contrast. In this study, all 36 (100%) women with VDD occurred at term (37–42 weeks) in contrast to 156 (70.9%) of normal occurring at term. This suggests that deficiency of vitamin D is more prevalent at term gestational age, explicable perhaps from increased demands for serum vitamin D with increasing pregnancy age to facilitate the development of soft tissues and bones of the growing fetus. This is, however, contrary to the observations made by Jan Mohamed et al.[30] and Singh[31] in India, who had in their different studies reported a decrease in VDD with increasing trimester of pregnancy.

VDD increased with a decreasing SC up to SC4; in this study, however, the difference was not statistically significant. The expectation would have been for VDD to be significantly lowest among the pregnant women of the highest SC (SC 1). The systematic review by Karras et al.[27] reported a controversial relationship between VDD and socio-economic status. The reason for this observed relationship between SC and VDD may not be unconnected to the fact that synthesis of vitamin D in humans in the tropical regions of the world with abundant sunshine is mostly from skin sources, rather than nutritional which would have caused a disparity in vitamin D availability between the women of the higher SC and those of the lower SC.[11]

Complexion (skin color) has an influence on serum vitamin D levels in the body, and this has been demonstrated in this study which shows that the light- and fair-skinned pregnant women had significantly higher levels of serum vitamin D compared with the dark-skinned women. VDD is therefore invariably higher among the dark-skinned pregnant women when compared with the others. This finding corroborates previous reports.[32],[33] Given exposure to the same amount of ultraviolet beam from the sun, light-skinned people tend to produce higher amounts of vitamin D when compared with the dark-skinned women, whose skin surface acts as a sunscreen preventing the penetration of the ultraviolet beam from the sun to effect cutaneous vitamin D synthesis.[34]

The role of exposure to sunlight may also have been responsible for the finding in this study of VDD being higher among women with indoor occupation, compared with those with outdoor occupation. Although some studies have reported no association between rural residence and serum vitamin D,[35],[36] this study indicates that all the pregnant women with VDD were domiciled in the urban area, indicating that place of domicile may have an influence on serum levels of vitamin D. The reason for this difference is not clear, which in fact requires further research. It is, however, tempting to suggest that differences in occupation, nutritional habit, and slum habitat which may occur between the urban and rural populace may negatively affect people residing in the urban area, increasing their disposition to VDD.

This study has examined the role of certain biosocial variables on the development of VDD in pregnant Igbo women of southeastern Nigeria, essentially to guide as to the need, or not for rational administration of vitamin D to pregnant women.

It shows that VDD significantly occurred in multiparous women, women of term gestational age, and those of dark complexion. It was also significantly associated with indoor occupation and urban domicile, whereas the consumption of certain foods that contain natural or supplements of vitamin D such as fish and margarine influenced VDD depending on the extent of their consumption. Adolescent, pre-pregnancy, and maternal nutritional supplements have been reported to play a vital role in the wellbeing and ultimate outcome of pregnancies.[37],[38],[39],[40],[41] As a result of previous studies which showed a positive relationship between vitamin D intake and serum level in pregnancy, the British Nutrition Foundation recommends that all pregnant and breastfeeding mothers be advised to take 10 µg of vitamin D daily.[42] In addition, in line with the above recommendation, the 2011 Institute of Medicine Report[43] and the Endocrine Society[44] advised a daily intake of vitamin D of 600 IU and 1500–2000 IU for pregnant and breastfeeding mothers, respectively. On the contrary, the WHO 2012 guidelines do not support the supplementation of vitamin D in pregnancy for the sole reason of improving maternal and neonatal health outcomes.[45] The controversy attendant on these two apparently contradicting recommendations may have arisen from the different quality of primary evidence used by the different organizations to arrive at their conclusion. Our findings suggest the recommendation of vitamin D supplementation in pregnancy on a specific basis, determined by special characteristics of the pregnant women including specific sociodemographic features. Pre- and early pregnancy administration of vitamin D supplement should therefore be recommended for categories of women whose biosocial characteristics are likely to predispose them to VDD. These include multiparous women, women at term gestational age, dark-skinned women, women of indoor work-place, and those of urban domicile.

Limitations to the study

This study is facility-based and may therefore not be representative of the entire Nigerian pregnancy population. This becomes even more important taking into consideration the fact that as high as 62% or more of pregnant women in Nigeria do not access antenatal care in orthodox health facilities. In addition, the study had been undertaken in southeastern Nigeria among a relatively better enlightened population, and the result cannot be extrapolated for pregnant women from other regions such as some states in northwestern Nigeria, with relatively lower educational status and poorer health-seeking behavior, where antenatal care from orthodox health facilities is below 10%.


The authors acknowledge the support of the Tertiary Education Trust Fund (TETFUND) in Nigeria through its sponsorship of this work via grants number TETF/ESS.D/6.11/NOM.RP/BAS&BNAS (BATCH 4 RP). We also like to acknowledge the contributions of the participants, field researchers, midwives, laboratory scientist, doctors, and heads of Department of Obstetrics and Gynecology of the two study facilities: Nnamdi Azikiwe University Teaching Hospital, Nnewi, and Holy Rosary Maternity hospital, Onitsha, for their respective roles played toward the successful completion of this work.

Authors’ contribution

JIBA: conceptualization, methodology, project management, funding acquisition, supervision; JEA: project administration, funding acquisition; EDA: project administration, writing—review and editing; JOU: investigation, resources, original draft preparation; ROE: writing—original draft preparation; NDA-O: writing—review and editing; and MME: formal analysis, data curation, and visualization, where applicable.

Financial support and sponsorship


Conflicts of interest

All the authors have no conflicting interests with respect to the publication of this work.

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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4]


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