Optimal birth weight is often seen as the primary indicator of a positive pregnancy outcome, while a low birth weight or a baby born small for gestational age (SGA) is indicative of impaired fetal development (Gluckman et al, 2005). However, cardiovascular disease (CVD), obesity, type 2 diabetes mellitus (T2DM) and depression associated with birth weights within the ‘normal’ range have also been observed (Jackson and Robinson, 2001). This suggests that nutritional factors play an important role in fetal development and pregnancy outcomes. Pregnancy is a time when the maternal diet is essential, not only for the health and wellbeing of the woman herself but also for the healthy development of the growing fetus. There has been more focus on maternal diet in recent years, highlighting the consequences of suboptimal nutrition in terms of pregnancy outcomes and long-term risks to offspring. There is a growing body of evidence linking maternal diet with an increased risk for adult-onset metabolic diseases such as T2DM, CVD and some cancers (Poston, 2011; Blumfield et al, 2012; Rao et al, 2012; Wood-Bradley et al, 2013). Research by Nyaradi et al (2013) has highlighted that micronutrients such as vitamin B12, folate, zinc and iodine play a role in the neurocognitive development of babies and children.
The majority of people in developed nations, including the UK, receive an adequate supply of micronutrients if they consume a balanced diet that meets their normal energy requirements and contains all the main food groups, such as: fruit and vegetables; milk and other dairy products; bread and cereals; and meat and non-meat alternatives. However, there are some vulnerable populations where these requirements may not be met, and pregnancy increases this risk (Berti et al, 2011).
Micronutrients
Micronutrients are defined as vitamins, minerals and trace elements. They are required in tiny amounts, for various essential functions, in either milligrams or micrograms per day, but have no calorific value (Bender, 2009). The required amounts are variable at population level but, for the avoidance of deficiencies, dietary reference values (DRVs) have been established for most micronutrients for women during pregnancy and lactation. DRVs are a guide to the amount of a particular nutrient that is sufficient or more than sufficient for the majority of the population. For vitamins and minerals, DRVs are defined as the reference nutrient intake (RNI) or lower reference nutrient intake (LRNI), and represent the upper and lower values of normal range for population requirements. The amounts recommended assume a normal population distribution, and may be insufficient for some pregnant populations, such as pregnant women with obesity and some ethnic minorities. Table 1 illustrates those micronutrients that have an additional requirement during pregnancy and/or lactation.
| Nutrient and DRV for females aged 19–50 years1 | Principal functions | DRV for pregnancy/lactation (per day) | Dietary sources | Deficiencies and symptoms |
|---|---|---|---|---|
| Vitamin A |
Visual pigments in retina, cell differentiation, antioxidant | 700 µg/900 µg | Liver, fish liver oils, vegetables (carrots), fats, milk and cheese | Night blindness; keratinisation of skin |
| Vitamin B1 |
Coenzyme in metabolism of carbohydrates, fat and alcohol | 0.8–0.9 mg*/1 mg | Cereals, cereal grain, beans, seeds, nuts, fortified foods | Beri Beri (peripheral nerve damage); Wernicke-Korsakoff syndrome (central nervous system lesions) |
| Vitamin B2 |
Coenzyme in oxidation and reduction reactions | 1.4 mg/1.6 mg | Milk and dairy products, meat (liver), eggs, green leafy vegetables if eaten in large amounts | Lesions to corner of mouth, lips, tongue; seborrheic dermatitis |
| Vitamin B6 |
Coenzyme in metabolism of amino acids | 1.2 mg‡/1.2 mg‡ | Nuts, meat, fish, wholegrain cereals and beans | Very rare but in extreme cases can cause disorders of amino acid metabolism and convulsions |
| Vitamin B12 |
Coenzyme in metabolism of folic acid and cell division | 1.5 µg‡/2.0 µg | Meat, eggs and dairy products | Pernicious anaemia |
| Folate† |
Coenzyme in single carbon transfer reactions | 300 µg/260 µg | Green leafy vegetables, yeast, liver, fortified cereals | Megaloblastic anaemia; implicated in neural tube defects during pregnancy |
| Vitamin C |
Co-factor for oxidase enzyme reactions, antioxidant, assists in absorption of non-haem iron, wound healing | 40–50 mg*/70 mg | Fruit and vegetables (including potatoes) | Scurvy, impaired wound healing, loss of dental cement, subcutaneous haemorrhage |
| Vitamin D |
Maintenance of calcium balances, enhances intestinal absorption of Ca2+, mobilises bone mineral | 10 µg/10 µg | Fats and oils, meat and meat products, fish, fortified foods, milk | Rickets (impaired bone mineralisation); osteomalacia (demineralisation of bone) |
| Calcium |
Bone and teeth formation and maintenance; nerve impulse transmission | 700 mg‡/1250 mg | Dairy, fish, meat, bread, spinach, watercress, broccoli, peas, tofu | Osteoperosis (reduced bone mass); hypertension (including pre-eclampsia), colon cancer |
| Iron |
Forms part of haemoglobin molecule that transports oxygen from lungs to tissues, component of various enzymes that regulate immune system functioning and energy production | 14.8 mg‡/14.8‡mg‡ | Haem iron from meat (liver) and fish; non-haem iron from legumes, green vegetables, nuts, dried fruits | Iron-deficiency anaemia: fatigue, restlessness, impaired cognitive performance, thermoregulation, immune response |
| Iodine |
Constituent of thyroid hormones thyroxine (T4) and triiodothyronine (T3) that modify development and growth, stimulate enzyme synthesis, oxygen consumption and basal metabolic rate | 140 µg‡/140 µg‡ | Milk, seafoods, iodised salt | Goitre (enlarged thyroid gland); congenital mental and growth retardation; pregnancy—cretinism in offspring |
| Magnesium |
Acts as a co-factor for enzymes requiring adenosine tri-phosphate; maintains electrical potential in nerve and muscle membranes | 270 mg‡/320 mg | Green leafy vegetables, cereals. Meat and animal products rich sources but simultaneous intakes of calcium and protein reduce bioavailability | Deficiencies very rare and only seen as a secondary complication of a primary disease state or as a result of rare genetic abnormalities of magnesium homeostasis |
| Phosphorous |
Component of nucleotides, nucleic acid and adenosine tri-phosphate; occurs as phospholipids, a major component of cellular membranes; supports tissue growth through pregnancy and lactation | 550 mg‡/990 mg | Ubiquitously found in all natural foods but rich sources include dairy products, meat, fish, eggs, tofu, vegetables | Deficiency only evident as a result of near total starvation |
| Selenium |
Integral component of glutathione peroxidases, potent intracellular antioxidant enzymes | 60 µg‡/75 µg | Fish, shellfish, red kidney beans, Brazil nuts, lentils, liver, pork | Keshan disease associated with selenium-depleted soil in areas of China; suboptimal selenium status may predispose to other deleterious conditions but can be ameliorated by vitamin E |
| Zinc |
Constituent of many regulatory and catalytic enzymes responsible for signal transduction and gene expression, structural role as zinc finger motifs in proteins, DNA and RNA | 7 mg‡/13 mg | Lean meat (offal), seafood, dairy, pulses, wholegrains | Growth retardation; in pregnancy: preterm birth, low birth weight |
DRV–dietary reference value
Committee on Medical Aspects of Food Policy (1991)
Last trimester only;
No increment
Recommendation for all women to take 400 µg folic acid supplement pre-conceptually until 12 weeks' gestation; women with previous pregnancy affected by neural tube defects recommended to take 5 mg folic acid
The majority of micronutrients can be derived from a variety of fresh, frozen and canned fruit and vegetables, wholegrains, legumes, beans and pulses, lean meats and up to two portions per week of oily fish (during pregnancy) (Williamson, 2006).
There are additional benefits to consuming fruit and vegetables. Most plant foods have a complex matrix containing many bioactive compounds, known as phytochemicals, in addition to multiple vitamins and minerals, and there is growing evidence to suggest that there is an additive and synergistic relationship between phytochemicals and micronutrients enabling optimum bioavailability, absorption and utilisation (Liu, 2013). Additionally, evidence suggests that many phytochemicals found in fruit, vegetables and wholegrains have antioxidant, anti-inflammatory, anti-obesity and chemopreventive properties (Williams et al, 2013).
There are also a number of fortified foods available including bread, breakfast cereals, spreads and beverages (Yang and Huffman, 2011). Fortified foods are one of the strategies used for modifying the diet at population level, the others being nutritional education and dietary supplements. However, there should be careful consideration given to dietary changes, ensuring the requirements of specific populations with regard to suboptimal or excessive intakes. Increasing availability of over-the-counter dietary supplements and (voluntarily) fortified foods has resulted in significant differences in micronutrient intakes within populations (Verkaik-Kloosterman et al, 2012). Consequently, safe upper limits have been set for a number of nutrients. The upper limit is defined as the highest level of a nutrient that can be consumed that is likely to pose no risk of adverse effects in the general population. Consumption of a nutrient in a quantity over the safe upper limit is likely to increase the risks of adverse effects, particularly in terms of damage to the developing fetus (Stanner, 2000). This is unlikely for most nutrients if consumed as part of a normal, balanced diet; however, concomitant intakes of fortified foods and dietary supplements may lead to excessive intakes. Additionally, many dietary supplements have ‘overage’ of nutrients, and nutrient content can deviate by as much as 25–50% from that stated on the label (Yetley, 2007). Overage ensures that the level of the nutrient at the end of shelf-life reflects the amount indicated on the product label; consequently, there may be significantly more than is stated at the start of the product's shelf-life (Expert Group on Vitamins and Minerals, 2003). Therefore, supplement use in the pregnant population must be determined as early as possible, and inappropriate usage deterred.
Groups at risk of deficiencies
There is risk of deficiencies of certain nutrients in some populations. Obese women (defined as having a body mass index (BMI) ≥ 30 kg/m2), underweight women (defined as having a BMI ≤ 18.5 kg/m2), adolescent girls, women from some ethnic minorities, vegetarians and vegans are at risk of impaired nutrient status, particularly during pregnancy and breastfeeding.
Teenage pregnancy
Adolescent females are particularly vulnerable during pregnancy as they are undergoing a period of growth and development in which there is a higher-than-usual requirement for nutrients. They are at greater risk of giving birth to low birth weight or SGA infants as a result of preferential nutritional partitioning (Jones et al, 2010). Data from the National Diet and Nutrition Survey (Bates et al, 2014) suggest that teenage girls are below the LRNI for a number of nutrients including calcium, iron and folate. The LRNI is the amount of a nutrient that may be sufficient for a small minority in the population with lower-than-normal requirements, but not enough for the majority. Moreover, there is likely to be competition for nutrients between the mother and fetus during an unplanned pregnancy (Williamson, 2006). The risk for anaemia and poor maternal nutrition is far greater in this group and, as such, increased neonatal mortality and morbidity—including intrauterine growth restriction (IUGR), SGA and preterm birth—is more likely (Treffers et al, 2001).
Pregnant teenagers are less likely to access maternity care in early pregnancy and are more likely to miss appointments, therefore missing out on essential early antenatal care and nutritional advice (Public Health England et al, 2015). Despite the increased risks, pregnant teenagers do not receive additional nutritional support, and advice is similar to that given to all pregnant women, with a recommendation for Healthy Start vitamins. Pregnant teenagers often have poor nutritional knowledge and inadequate dietary intakes; health professionals are in a position to educate them of the importance of a healthy, balanced diet during pregnancy or, if necessary, signpost them to a registered nutritionist or dietitian (Derbyshire, 2007). Montgomery (2003) suggests that making it as easy as possible for pregnant teenagers—by focusing on foods, rather than nutrients, and rewarding effort—may help them to optimise their nutrition.
Ethnic minorities
People with darker skin tones are less able to synthesise vitamin D, so women from some minority ethnic groups are at risk of vitamin D deficiency. In addition, some cultural dress codes limit exposure to sunlight, and a lack of foods rich in vitamin D in the diet may also contribute to a deficiency (Judd, 2013). Some women may be more likely to be vegetarian and/or have dietary restrictions because of religious practices.
These factors have resulted in a resurgence of rickets in children, compounded by extended duration of breastfeeding and a lack of exposure to sunlight. Part of this could be due to public health messages regarding sun exposure and skin cancer. Rickets may also be a result of calcium deficiency; as such, calcium status should be assessed in addition to plasma 25-hydroxyvitamin D (25(OH)D), which is the concentration measured to determine vitamin D status (Allgrove and Mughal, 2014).
Women who have travelled to the UK from developing countries may be deficient in other nutrients, such as iron, zinc, vitamins A, B6, B12, C, E and riboflavin as a consequence of inadequate meat, fruit and vegetable intakes (Zerfu and Ayele, 2013). Iron-deficiency anaemia is the most prolific nutrient deficiency in the world and has implications for low birth weight and preterm birth. Supplementation of iron during pregnancy may be insufficient to restore iron stores and correct the effects of anaemia (Scholl, 2011).
Vegetarians and vegans
Vegetarians and vegans present nutritional challenges during pregnancy as nutritional intakes can vary as much in these groups as the general population (Tyree et al, 2012). Nutrient intakes in vegetarian and vegan populations of calcium, vitamin B12, riboflavin and iodine have been shown to be below the RNI, particularly in vegans. Intakes for iron and zinc may also be vulnerable because of the exclusion of meat and fish from the diet. However, the majority of these requirements can be met with careful dietary planning and the inclusion of some fortified foods (Williamson, 2006); this is more likely to be achieved with the support and/or supervision of a registered dietitian or nutritionist. Physiological adaptations during pregnancy enable increased iron absorption as the need for iron increases throughout gestation. However, dietary intake alone is insufficient to ensure optimum utility and is, therefore, dependent on existing pre-pregnancy iron stores (Hallberg, 2001). As such, in the vegetarian and vegan population, pre-natal iron supplementation may be necessary to ensure sufficient iron stores to adequately sustain pregnancy and lactation.
Obesity
The risks for adverse pregnancy outcomes are increased in the obese population. Maternal risks include gestational diabetes mellitus (GDM) and hypertensive disorders, including pre-eclampsia. Fetal risks include macrosomia, neural tube defects (NTDs), IUGR and genetic malformations (Cnattingus et al, 1998; Sebire et al, 2001). Inadequate dietary folate intake in the pre-conceptual period is associated with an increased risk for NTDs (McMahon et al, 2013) and evidence from randomised controlled trials shows an inverse dose-response relationship between folate status and NTDs (Scientific Advisory Committee on Nutrition (SACN), 2006). Therefore, the National Institute for Health and Care Excellence (NICE, 2008) recommends all women take a 400 µg/day folic acid supplement pre-conceptually until at least 12 weeks' gestation. However, women with BMI ≥ 30 kg/m2 and women at increased risk of having a baby born with a NTD are recommended to take a 5 mg/day folic acid supplement (Royal College of Obstetricians and Gynaecologists, 2014). This includes women who have previously had a baby born with a NTD, women with diabetes and women with a genetic variant of specific genes that code for enzymes associated with folate metabolism (SACN, 2006).
Inadequate maternal nutrition is implicated in adverse pregnancy outcomes. Pregnant women with obesity are at increased risk of micronutrient deficiencies, often due to eating behaviours and a reliance on energy-dense, nutrient-poor foods (Moran et al, 2013). Nutritional data for pregnant women with a BMI ≥ 35 kg/m2, gathered as part of the Fit for Birth study at Liverpool Women's Hospital, demonstrated that although total energy intakes were only slightly below estimated average requirements for energy, many of the women were below RNI for a range of micronutrients including iron, vitamin D, folate, iodine and calcium. When micronutrients were measured as a ratio of total energy, it was found that intakes declined between 16 weeks' and 36 weeks' gestation. These findings suggest a dilution of micronutrients, further compounded when levels of under-reporting are taken into consideration (Charnley, 2015).
Pregnant obese women are in need of increased nutritional support; a multidisciplinary antenatal approach is advocated, with direct referrals to dietetic services in line with NICE (2010) guidelines. A number of recent lifestyle intervention trials are nearing completion in which a multidisciplinary approach is being taken. These studies have all looked at behaviours in terms of dietary intake, physical activity levels and lifestyle. The UPBEAT trial (Poston et al, 2013), the Lifestyles course (Smith et al, 2010) and the HELP trial (Jewell et al, 2014) are all aimed at improving pregnancy outcomes in the obese pregnant population using behavioural change techniques.
Underweight
Underweight or low BMI (≤ 18.5 kg/m2) is associated with impaired fertility (Williamson, 2006), and underweight women who do conceive have a 72% increased risk of miscarrying in the first trimester compared to women within the normal weight range (Bainbridge, 2007). Maternal underweight is also known to have an impact on neonatal morbidity. A growing number of studies have shown that maternal underweight significantly increases the risk of low birth weight, SGA and preterm birth (Salihu et al, 2009; Han et al, 2011; Jeric et al, 2013). Low birth weight and IUGR have been identified as predictors for long-term adult health risks such as coronary heart disease and T2DM as a result of suboptimal nutrition in utero and fetal programming (Osmond and Barker, 2000; Gluckman et al, 2005; Barker et al, 2010). There is also evidence to suggest an association with pre-pregnancy maternal underweight and neurocognitive development in offspring. A study by Polańska et al (2015) showed decreased language skills at 12 months and cognitive and motor development at 24 months in the offspring of women with a BMI ≤ 18.5 kg/m2.
Socioeconomic status
Obesity and underweight are both associated with low socioeconomic status (Doak et al, 2005) and it is not uncommon to find both ends of the spectrum coexisting in some deprived wards. This was highlighted in a study in Liverpool, in which women's height, weight and BMI data, along with their postcodes, were mapped using a geographical information system, and ‘hotspots’ identified (Abayomi et al, 2009). A study by Fowles (2002) looked at differences between low-income and middle-income women in the USA in terms of nutritional knowledge, dietary intakes and weight gain during pregnancy. The study showed that weight gain in women with a low pre-pregnancy BMI was lower than that of women who had a high pre-pregnancy BMI, who tended to gain more weight than that recommended by the Institute of Medicine. Additionally, the study found that nutritional requirements for pregnancy had not been achieved in either of the groups, even though energy from carbohydrate and protein intakes and percentage of energy from fat exceeded recommendations, as did that of sodium. Dietary records showed increased consumption of bread and fried or processed meat products, such as fried chicken and hotdogs, in the low-income group. This suggests that positive dietary changes before and during pregnancy would help to improve both maternal wellbeing and neonatal outcomes.
Pregnancy following bariatric surgery
Another subset of pregnant women requiring attention is those who have undergone bariatric surgery prior to becoming pregnant. This is a relatively new procedure, and the possible repercussions of bariatric surgery on the long-term health of offspring have yet to be observed. Bariatric surgeons advise women to leave a minimum of 18 months following surgery before attempting to conceive to allow for weight stabilisation, thus decreasing the risk of maternal and fetal malnutrition resulting in SGA (Edwards, 2005). However, a study by Devlieger et al (2014) looking at the nutrient status of 49 pregnant women (18 following restrictive surgery and 31 following malabsorptive surgery) found that most nutrients were depleted at 12 weeks' gestation and declined significantly throughout pregnancy, despite self-reported intakes of supplements during trimester 1 and additional supplement intake during trimesters 2 and 3.
An earlier study by Pelizzo at al (2014) highlighted three clinical cases of fetal neural defects and malnutrition during pregnancy in women following bariatric surgery. None of the three women took nutritional supplements following their surgery, nor did they take advantage of nutritional surveillance or counselling. Only one of the women was taking supplements prior to conception, but stopped within 6 weeks' gestation. The other two women began taking nutritional supplements between 20–22 weeks' gestation, but all three were deficient in a number of nutrients including vitamin A, vitamin B12 and the active form of vitamin D.
Women who have undergone bariatric surgery are reliant on dietary supplements to sustain optimal health and there is the possibility of a conflict between maternal and fetal health status. However, both these studies suggest that compliance with nutritional supplement regimens is poor in many women following bariatric surgery, despite becoming pregnant (Devlieger et al, 2014; Pelizzo et al, 2014). It is likely that some general recommendations may not be appropriate to this group, particularly with regard to the avoidance of vitamin A and recommended intakes of 400 μg/day folic acid. There are also nutritional concerns regarding the quality of breast milk in post-bariatric women who have undergone malabsorptive surgery. Inadequate serum vitamin B12 levels observed in some lactating women may result in neonate deficiency, and fat malabsorption may reduce the energy available in breast milk, potentially affecting infant growth (Harris and Barger, 2010). This suggests that careful pre-conceptual nutritional planning and increased postpartum nutritional monitoring may be required in this population.
Nutritional support
All pregnant women require nutritional support throughout pregnancy, to ensure optimal outcomes. However, vulnerable population groups present greater challenges to dietitians and nutritionists. Nutritional assessment is necessary to determine the adequacy of dietary intakes and establish personalised requirements.
Supplementation
NICE (2010) guidelines state that women who present for maternity services or health visitor appointments should receive healthy eating advice, and those with a BMI ≥ 30 kg/m2 should be offered a structured weight-loss programme following childbirth. All pregnant women are advised to take 400 μg/day folic acid and to eat foods that provide a rich source of folate or folic acid. For women who have a family history of NTDs, have had a baby with a NTD or if the woman has pre-existing diabetes, 5 mg/day is recommended. Evidence suggests that folic acid taken 12 weeks prior to conception and 28 days post-conception is most effective in reducing the risk of NTDs, and that folic acid supplements taken in the later stages of pregnancy confer no additional benefit (Lassi et al, 2013).
Vitamin D status in breastfed infants is entirely dependent on the vitamin D status of the mother; therefore, a vitamin D supplement of 10 μg/day is now recommended for all pregnant and breastfeeding women (NICE, 2014).
NICE guidelines recommend specific supplements such as folic acid, vitamin C and vitamin D. Iron supplements are also prescribed by GPs in some cases, if haemoglobin levels are below 110 g/L during the first trimester or 105 g/L at week 28 of pregnancy, which are considered outside the normal range in the UK (SACN, 2010). Healthy Start vitamins for pregnant women currently contain 70 mg vitamin C, 10 μg vitamin D and 400 μg folic acid. However, it has been suggested that the 10 μg/day vitamin D recommended may be insufficient for high-risk groups and there is a need for trials to identify vitamin D intakes that would optimise circulating levels of 25(OH)D3 (SACN, 2007). Women in receipt of welfare benefits who are signed up to the Healthy Start scheme receive vitamins for free, available via antenatal clinics and children's centres (NICE, 2008). Some local authorities, including Liverpool, make the supplements available to all pregnant women, but they are not free of charge in all local authorities (NICE, 2014).
It is generally acknowledged that additional micronutrient supplementation may support pregnancy, owing to the demands that pregnancy places on the body. However, the mechanisms by which micronutrient supplementation affects pregnancy outcomes are not fully understood (Bekker, 2009). It is postulated that improved immune function may reduce the risk of infection, thereby preventing preterm birth; supplementation may also improve energy metabolism and anabolic processes, leading to a decrease in IUGR prevalence as well as improving the maternal response to stress (Shah and Ohlsson, 2009). However, there is insufficient evidence attributing a deficiency of a specific nutrient to an adverse pregnancy outcome (Keen et al, 2003).
The use of supplements in certain populations has proven to be effective in mitigating the risks of low birth weight babies—of which there is a higher prevalence in the UK than in other EU and developed countries (Ashdown-Lambert, 2005)— along with SGA babies and preterm births. This is particularly apparent in poorer countries.
Limitations of dietary supplements
With the exception of folic acid for the prevention of NTDs and vitamin D supplementation, there is insufficient evidence of any conferred benefit to pregnant women in developed countries from nutritional supplements (Picciano, 2003). A review of interventions—including 23 trials involving over 76 000 women—assessed the effectiveness of multiple micronutrient supplements (MMS) in comparison to single micronutrient supplements. The findings suggested a positive effect on reducing SGA and low birth weight babies, but no statistically significant differences for any other pregnancy outcome including preterm births, miscarriage or maternal and neonatal mortality (Haider and Bhutta, 2015).
Women should be assessed with regard to supplement use and, in developed countries such as the UK, more consideration needs to be given to maternal diet. This should be reviewed as part of antenatal care to ensure there is no risk of interactions between nutrients, which may affect the bioavailability, absorbency and/or utilisation of a nutrient; for example, iron inhibits the absorption of zinc, and calcium impairs the absorption of iron (Expert Group on Vitamins and Minerals, 2003). Additionally, nutrient–pharmaceutical interactions may either impair drug efficacy or inhibit nutrient absorption as a result of supplementation (Yetley, 2007). There is insufficient information on what constitutes the optimal micronutrient supplement in pregnancy, what nutrients should be included, in what form, and when they should be taken (Keen et al, 2003). The consensus is that all women of reproductive age in developed nations should be made aware of the importance of a nutrient-rich dietary intake during pregnancy to ensure optimal pregnancy outcomes (Williamson and Wyness, 2013).
The use of MMS should be approached with caution. While the use of supplements may be able to mitigate adverse outcomes in certain populations, there remains a question over optimal amounts, and in some cases it has been shown that over-consumption may increase adverse outcomes. Animal model studies have also alluded to the possibility that higher micronutrient intakes during pregnancy may be implicated in the risk for adult disease in offspring when exposed to an obesogenic diet post-weaning (Reza López et al, 2013).
Conclusion
Given the transgenerational impact of inadequate nutrition, it is sensible to encourage pregnant and breastfeeding women to consume nutrient-rich foods to encourage positive weaning and early feeding practices. It is important that pregnant women are well-informed about optimal nutrition and that they derive their required nutrients from dietary sources where possible. It could be argued that, if supplements are going to have any effect, they should be taken pre-conceptually, as most complications of pregnancy arise in the first few weeks following conception.
The traditional idea of pregnant women ‘eating for two’ applies not to quantity of food but, crucially, to quality. A healthy, balanced diet during pregnancy and breastfeeding will provide optimal maternal health, with the potential to reverse the obesity trend and reduce the risk of metabolic diseases in the adult offspring. There cannot be a one-size-fits-all approach to nutrition and supplementation during pregnancy. Individuals have differing needs that often go beyond the remit of midwives, requiring more detailed and/or personalised nutritional assessment and dietetic advice. While Healthy Start vitamins are appropriate for many pregnant women, they may be insufficient for others who are at risk of nutritional deficiencies, including vitamin A. Nutritional assessment and counselling should be made available to nutritionally vulnerable groups, and a multidisciplinary approach is required, where midwives can refer or signpost women to appropriately qualified dietitians or nutritionists. Barger (2010) outlined the effects of inadequate maternal nutrition on perinatal outcomes and advocated nutritional counselling, suggesting women complete a form of dietary recall prior to antenatal appointments; this would be a way of screening for vulnerable populations, who can then be referred appropriately.
Further reading
This article highlights micronutrient and supplement intakes during pregnancy; energy and macronutrient intakes are beyond its scope. Readers wishing to learn more on this are directed to the following paper: Blumfield ML, Hure AJ, Macdonald-Wicks L, Smith R, Collins CE (2012) Systematic review and meta-analysis of energy and macronutrient intakes during pregnancy in developed countries. Nutr Rev 70(6): 322–36. doi: 10.1111/j.1753-4887.2012.00481.x