Guidance from the National Institute for Health and Care Excellence (NICE) (2008, 2017a; 2017b) and Royal College of Obstetricians and Gynaecologists (RCOG) (2014a) recommends vitamin D supplementation to all pregnant women in the UK. Internationally, however, there is much dispute as to whether this is of benefit to mother and fetus/neonate, and indeed the World Health Organization (WHO) does not recommend routine antenatal supplementation (WHO, 2016). There is a dearth of evidence to underpin antenatal supplementation, and although it is known to increase maternal vitamin D levels, there is no consensus as to what effect this has on maternal or fetal wellbeing (De-Regil et al, 2016). However, it is acknowledged that supplementation is unlikely to cause harm (RCOG 2014a), so while awaiting more robust evidence, midwives can continue to recommend supplementation in line with national guidance (NICE, 2017b).
This leaves midwives in a challenging position, needing to go beyond superficial advice and explore the underpinning physiology to ensure that women are receiving accurate, evidence-based information (Maher and Lowe, 2015).
The majority of women meet health professionals regularly during the childbearing continuum, so this is an optimum time for women to receive personalised information to promote health and wellbeing (NICE, 2017b). As frontline practitioners throughout pregnancy and the puerperium, midwives acknowledge that health promotion is a fundamental element of their role, and they are ideally positioned to initiate conversations with women regarding vitamin D.
Personalising care is key, as there are a variety of barriers that mean that, despite recommendations, the uptake of vitamin D in pregnancy remains low (Windrim et al, 2017; Barnes et al, 2016).
This article will explore the public health issue of vitamin D supplementation in pregnancy, considering the physiology and evidence underpinning supplementation. How midwives can integrate this knowledge into conversations with women and their families will also be examined, exploring how this midwifery translation can break down barriers and ensure that all women are empowered to make informed choices.
Underpinning physiology
Vitamin D is a fat-soluble vitamin that is primarily made by synthesis in the skin following sunlight exposure, although it also has some dietary sources (RCOG, 2014a; NICE 2016). Vitamin D has a variety of actions, including regulating levels of calcium and phosphate, contributing to healthy bone metabolism, maintaining blood glucose levels, supporting insulin secretion, ensuring lung development and promoting immunity (Finer et al, 2012; Thorne-Lyman and Fawzi, 2012; Xuan et al, 2013; Karras et al, 2014; RCOG, 2014a). Optimal levels of vitamin D can therefore protect against a variety of disorders, making vitamin D in pregnancy and the puerperium a public health priority for midwives (Pludowski et al, 2013; Sanders and Lamb, 2015) (Table 1).
| Mother | Fetus/neonate |
|---|---|
| Hypertension | Low birth weight |
| Pre-eclampsia | Hypocalaemic seizures |
| Impaired glucose tolerance in pregnancy | Impaired skeletal development and growth |
| Bacterial vaginosis | Impaired fetal lung development |
| Increased caesarean section rates | Childhood immune disorders |
| Association with psychiatric illnesses |
The northerly latitude of the UK means that residents are particularly at risk of vitamin D deficiency, as the amount of vitamin D obtained from sunlight exposure depends on a multitude of factors, including extent of exposure, cloud cover, latitude, altitude and season (Rhodes et al, 2010; NICE, 2016; Emmerson et al, 2018). Using sunscreen diminishes vitamin D synthesis further still, with a sun protection factor (SPF) of 8 or more almost entirely preventing vitamin D formation. An SPF of 30 is thought to reduce the capacity of the skin to produce vitamin D by 95-98% (Holick and Garabedian, 2006; Holick, 2007; Wacker and Holick, 2013). Skin pigmentation also affects vitamin D synthesis: 30 minutes of sun exposure for a Caucasian adult is thought to deliver 5000IU of vitamin D (Yu et al, 2009), whereas women with type VI skin pigmentation (as classified by the Fitzpatrick (1988) scale) produce up to one-sixth of this, thus requiring significantly longer sun exposure (Chen et al, 2007; Engelsen, 2010; Shin et al, 2010).
The richest dietary source of vitamin D is oily fish, including salmon, mackerel, tuna, sardines, pilchards, kippers, trout and eel. Egg yolks, mushrooms and meat also contain vitamin D, although this can be season-dependent. Additionally, some foods are fortified with vitamin D such as margarine, milk, yogurt, cheese, cereals and breads (Holiss and Wagner, 2004; Holick, 2007; British Dietetic Association (BDA), 2013; Wyness, 2014). The amount of vitamin D in individual food sources can vary widely, with a difference of 400-600IU depending on food farming processes (Lu et al, 2007; BDA 2013).
These challenges in endogenous vitamin D production have led to widespread deficiency, becoming a common concern worldwide (Palacios and Gonzalez, 2014). Deficiency in pregnancy is more concerning still, as the fetus is entirely reliant on maternal vitamin D sources for development (RCOG, 2014a).
Health promotion and supplementation
Vitamin D continues to be a major public health issue due to widespread global deficiency (Saraf et al, 2016; Lepsch et al, 2017). Studies have found a high prevalence of deficiency (Mithal et al, 2009; Palacios and Gonzalez, 2014), despite programmes to increase education and supplementation uptake. It is estimated that 1 billion people worldwide have low levels of vitamin D (Holick and Chen, 2008) with European levels of insufficiency varying widely (Lips, 2007; van Shoor and Lips, 2011).
With much of the research coming from low- or middle-income countries, there is widespread debate about whether these recommendations are truly applicable in a UK setting (Bouillon et al, 2013; Drug and Therapeutic Bulletin (DTB), 2016). Yet, despite continued guidance to increase supplementation levels, many women in the UK remain at risk of vitamin D deficiency during pregnancy and in the postnatal period.
The best gauge of vitamin D status is the concentration of circulating 25 hydroxy vitamin D (Fraser and Milan, 2013), assessed through the measurement of serum levels, although it must be acknowledged that other metabolites have significant clinical value (Fraser and Milan, 2013). Optimal levels of vitamin D are widely debated, and therefore cut-off ranges vary considerably across the literature. Many studies cite deficiency as a level of <25nmol/l (10ng/ml), with levels of <50-75nmol/l (20-30ng/ml) showing insufficiency or a borderline sufficient level (Holick and Chen, 2008; Mithal et al, 2009; Palacios and Gonzalez, 2014; Heyden and Wimalawansa, 2017), which can make interpretation of studies more complex. According to NICE (2017b), midwives need to emphasise the importance of vitamin D to pregnant and breastfeeding women, particularly teenagers and younger women, as well as at-risk groups (Table 2) (Scientific Advisory Committee on Nutrition (SACN), 2016).
| Situation | Advised dosage |
|---|---|
| All pregnant women | 400IU |
|
Risk factors:
|
1000IU |
| Women at risk of pre-eclampsia or women with pre-existing gastrointestinal conditions | 800IU |
No agreed level of optimum vitamin D exists, therefore there is no definitive consensus about recommended intake (Theodoratou et al, 2014), making translation of guidance and recommended doses open to interpretation. Because of the scarce information to ascertain either the beneficial or harmful results of routine supplementation, WHO (2016) does not recommend routine supplementation for antenatal care. However, UK national guidance recommends supplementation for the general pregnant population of 10 micrograms (400 IU) per day (RCOG, 2014a; NICE, 2017b). This advice and supplementation amounts are also supported by SACN, which changed its stance on vitamin D in 2010. Reference nutrient intake (RNI), or safe intake, values have been generated to safeguard the populations in terms of satisfactory status for the protection of musculoskeletal health. RNIs are essential because it is impossible to gauge the impact of sunlight exposure for dietary reference value because of the multiple factors impacting endogenous synthesis (SACN, 2016). RNI is not a minimum amount that women should aim to meet, but rather the risks of deficiency are lowered by supplementing in this way (NICE, 2017b).
Because no general screening is offered for women throughout pregnancy, this RNI also safeguards those women who are at-risk. National screening is costly compared to general supplementation, although some argue that certain pregnant women should be offered a screening test, such as women with additional risk factors (RCOG, 2014a). However, the most recent Cochrane review suggests that the value of routine vitamin D supplementation to improve maternal and neonatal outcomes is unclear (De-Regil et al, 2016). Unless further research is conducted, the best available information is woefully inadequate to provide concrete decisions about supplementation safety and worth (De-Regil et al, 2016). This lack of screening also places further reliance on midwives, as well as other frontline staff, to recognise and correct vitamin D deficiency, making it necessary for midwives to be confident with the identification of higher-risk groups and willing to take positive actions to address barriers to healthy vitamin D stores (Heyden and Wimalawansa, 2017). National bodies have called for health professionals to emphasise the importance of supplementation and uptake of vitamin D (RCOG 2014a; SACN, 2016; NICE, 2017b), thus situating the midwife as one of the primary public health advocates.
Although Steer (2015) argues that routine supplementation has potential detrimental health implications as there is no long-term data on which to measure health outcomes, much of the literature continues to press for further action and rigorous nutritional counselling from midwives (Antonakou, 2017). Some practitioners have even urged that supplementation is as much of a public health issue as vaccination (Högler, 2015).
Conversations to break down barriers
During the initial booking contact with women, it is recommended that midwives discuss supplementation, educating women and their families about the significance of vitamin D in pregnancy and the puerperium (RCOG, 2012; RCOG 2014b; NICE, 2017b). This initial conversation should include assessing risk status, counselling women about the evidence-based guidance on supplementation and advising how women can increase their endogenous vitamin D levels.
During brief antenatal contacts, midwives need to embed into general discussions not only the importance of folic acid (Cawley et al, 2016) and vitamin D, but should also emphasise the relationship between nutritional and vitamin intake and fetal health (NICE, 2017b). Personalising care in this way, taking into account cultural diversities, ethnicity and socio-cultural demographics, enables the woman to receive relevant information tailored to their own family and needs (Lamb and Sanders, 2015; Sanders and Lamb, 2015; NICE, 2017b).
Midwives must seek to understand the reasons why women may not prioritise vitamin D uptake during pregnancy and breastfeeding, working towards informing women of the benefits maternal health in pregnancy and emphasising the impact on fetal wellbeing.
Cultural and language challenges
NICE (2017b) recommend that midwives ensure that information is culturally appropriate, and this is particularly relevant when considering that at-risk groups for vitamin D deficiency include those who have limited access to sunlight for both cultural and social reasons (Table 2) (Engelsen, 2010; Harvey et al, 2014). Information should be tailored for local communities and take into consideration cultural and religious beliefs as well as practical language and literacy skills (Arrish et al, 2017; NICE, 2017b).
Counselling women about public health issues can be challenging, particularly when language barriers exist or cultural practices differ. Unfamiliarity with healthcare systems and difficulties in communicating with health professionals may mean that those who have difficulty reading or speaking English may not fully access antenatal care (NICE, 2010). This makes each contact with a midwife particularly essential as an opportunity to promote health and lifestyle choices (NICE, 2013). Using a variety of different communication methods, such as providing written information in native languages and using translation services, is essential to ensure that accurate information is provided, particularly when discussing detailed information such as vitamin supplementation dosage (NICE, 2010).
Offering increased frequency of antenatal contacts and being flexible with appointment length when translation services are used, are important aspects for midwives to consider when personalising care (NICE, 2010).
Fetal/maternal health priorities
It is suggested that fetal bone health is dependant on maternal stores of vitamin D (Barrett and McElduff 2010; Kovacs, 2013; Wyness, 2014; Högler, 2015), but conversations about diet in pregnancy and infant feeding can be challenging for midwives, with associated factors such as body mass index (BMI), financial implication and ethnic and cultural practices needing sensitive negotiation (Lee et al, 2012; de Jersey et al, 2013; Arrish et al, 2017).
Women in pregnancy are profoundly invested in fetal health (Lamb and Sanders, 2015), obtaining a sense of maternal reassurance through supplementation that fetal needs are being met (Malek et al, 2018). Women may prioritise fetal health over self-care, and so presenting the potential impact of fetal and maternal benefits of supplementation in a balanced and evidence-based manner can enable women to make fully informed decisions based on their own health priorities. This could ensure that uptake choices are truly informed for families at risk of symptomatic vitamin D deficiency, through thorough and holistic advice (Ferrari et al, 2013; Wennberg et al, 2013).
Confusion and lack of knowledge
Many women may still be unaware of the need for vitamin D supplementation (Windrim et al, 2017), and with many vitamin supplements heavily marketed at women during the antenatal and postnatal periods (DTB, 2016; Malek et al, 2018) there is an array of conflicting information, which leads to uncertainty about dosages and supplementation choices (Barnes et al, 2016).
Midwives should acknowledge that women often do not follow specific dietary advice, reporting confusion surrounding nutrition and feelings of guilt when unable to make positive changes (Wennberg et al, 2013; Aubuchon-Endsley et al, 2015; Lamb and Sanders, 2015). Poor nutritional knowledge can be a barrier to obtaining optimal levels of vitamin D, but this is also dependant on the knowledge of the midwife (Arrish et al, 2017). Discussions between a woman and her midwife must be personalised to allay these confusions and be relevant to each woman's circumstance. This in turn could develop women's sense of self-efficacy which has been shown to increase supplementation compliance levels (Barker et al, 2017).
Midwives taking a partnership approach allows women to understand the public health context and view vitamin uptake for neonatal health, making sense of continuing vitamin supplementation into their postnatal breastfeeding experience. This can therefore improve vitamin D stores in the neonate, rather than stopping at the end of pregnancy (Rodda et al, 2015; Thiele et al, 2017).
Women are also heavily influenced by their closer communities of support, including friends and families (Pouchieu, 2013), and so health professionals need to supply advice and information with these extended support systems in mind, to increase awareness across the wider community.
Socioeconomic implications
Multivitamins are expensive and midwives need to situate the importance of simple vitamin preparations of folic acid and vitamin D to ensure that they cater for the widest demographic of patients, although cost as a barrier appears to be of more maternal concern postnatally (Malek et al, 2018). Other issues may affect women's vitamin uptake of vitamin D, however, of which midwives may not be aware. For instance, the number of UK families fed by foodbanks continues to rise at a concerning rate (Jitendra et al, 2017).
Vitamin vouchers can provide supplementation for women and children from 6 months to 4 years and schemes such as Healthy Start provide a ‘nutritional safety net’ for families on benefits or from disadvantaged backgrounds (Department of Health, Social Services and Public Safety et al, 2018; NICE, 2008; 2017c; 2017b). Midwives are gatekeepers to these services for women and can provide information and access.
Day-to-day challenges
Women may also find supplementation with multivitamins challenging because of pregnancy related issues including hyperemesis, morning sickness and nausea, although this can be a reason for continuing to use, as dietary needs may not be met otherwise (Malek et al, 2018). Some of the barriers for supplementation compliance are simple issues, such as forgetting, difficulty in swallowing larger tablets and being put off by side effects (Barbour et al, 2012; Barker et al, 2017).
These issues can also have a psychological impact and potentially feed into women's concerns that if they choose not to be compliant with health professionals' advice, this may negatively situate their parenting ability (Malek et al, 2018). Creating a supportive environment and positive rapport with women is an essential midwifery skill in order to facilitate a safe space in which women can confide.
Conclusion
Despite explorations of the public health issue of widespread vitamin D deficiency, there remains a dearth of information regarding the longer term implications of supplementation on maternal and neonatal health (De-Regil et al, 2016). Additional high-quality trials with larger sample sizes are needed to be able to draw definite conclusions on the effectiveness of supplementation and any potential positive outcomes for certain higher-risk groups. However, there is a general consensus that supplementation is not harmful, and may provide short and long term benefits (RCOG, 2014a).
Women present for midwifery care with an increasingly diverse range of circumstances, including social issues women may be reluctant to divulge. Some of these issues may only be revealed by sensitive and personalised discussion with their midwives.
Midwives need to be confident in identifying and correcting low levels of vitamin D for the women in their care, catering specific information and achievable advice regarding supplementation, nutrition and safe sunshine exposure (Heyden and Wimalawansa, 2017). However, midwives should also acknowledge that women often do not follow specific dietary advice, reporting confusion surrounding nutrition and feelings of guilt when unable to make positive changes (Wennberg et al, 2013; Aubuchon-Endsley et al, 2015; Lamb and Sanders, 2015). Women are heavily influenced by their closer communities of support including friends and families (Pouchieu, 2013) and so health professionals need to supply advice and information with these extended support systems in mind, to increase awareness across the wider community.
National guidance situates dietary importance and promotion of vitamin D as a high priority for midwifery communication (RCOG, 2014a; NICE, 2017b). Subsequently, midwives must ensure that knowledge is evidence-based so they can not only refer to the wider multidisciplinary team when deficiency is suspected, but also facilitate a shared care approach, empowering women with evidence to inform individual nutritional needs (Antonakou, 2017).