Antioxidant Nutrients in Pregnancy: a Systematic Review of the Literature

Status of Retinoids and Carotenoids and Associations with Clinical Outcomes in Maternal-Infant Pairs in Nigeria

Vitamin A is an essential nutrient in pregnancy, and other carotenoids have been independently associated with maternal-infant outcomes. The objective of this study was to quantify the status of vitamin A and carotenoids in Nigerian maternal-infant pairs at delivery, compare these to a cohort from a developed nation, and determine the impact on clinical outcomes. Maternal and cord blood samples were collected in 99 Nigerian mother-infant pairs. Concentrations of lutein + zeaxanthin, β-cryptoxanthin, lycopene, α- and β-carotenes, and retinol were measured using HPLC. Descriptive statistics were calculated and Spearman coefficients were used to assess correlations between maternal and cord measurements; Mann-Whitney tests were used to compare median plasma values between dichotomous variables. Linear regression models were used to adjust for relevant confounders. A p < 0.05 was considered statistically significant. Thirty-five percent of mothers had plasma retinol concentrations ≤0.70 µmol/L; 82% of infants had plasma retinol concentrations ≤0.70 µmol/L at delivery. Maternal and infant concentrations of vitamin A compounds were highly correlated and were associated with newborn growth and Apgar scores. Despite plasma concentrations of pro-vitamin A carotenoids higher than those reported in other populations, pregnant Nigerian women have a high prevalence of vitamin A deficiency. As vitamin A related compounds are modifiable by diet, future research determining the clinical impact of these compounds is warranted.

Small-for-gestational-age birth and maternal plasma antioxidant levels in mid-gestation: a nested case-control study

OBJECTIVE

To assess whether maternal plasma antioxidant levels in mid-pregnancy are associated with small-for-gestational-age (SGA) birth.

DESIGN

Case-control study nested within a population-based cohort study.

SETTING

Four hospitals in Montreal, Canada.

POPULATION

Pregnant women recruited before 24 weeks of gestation, whose pregnancies were not complicated by pre-eclampsia or preterm delivery.

METHODS

Blood samples were obtained at 24-26 weeks and assayed for nutritionally derived antioxidant levels in SGA cases (n = 324) and randomly selected controls with birthweights between the 25th and 75th centiles (n = 672). We performed logistic regression analyses using the standardised z-score of each antioxidant as the main independent variable, after summing highly correlated antioxidants or combining via principle component analysis. We adjusted for risk factors for SGA that were associated with antioxidant levels.

MAIN OUTCOME MEASURES

SGA, birthweight <10th centile for gestational age and sex.

RESULTS

Retinol was positively associated with risk of SGA (adjusted odds ratio [OR] 1.41; 95% confidence interval [95% CI] 1.22-1.63, per SD increase). Carotenoids (log of the sum of β-carotene, lutein/zeaxanthin, α- and β-cryptoxanthin) were negatively associated with SGA (adjusted OR 0.64; 95% CI 0.54-0.78, per SD increase). We found no significant associations between SGA and lycopene or any of the forms of vitamin E assessed, including α-tocopherol, corrected α-tocopherol (per nmol/l of low-density lipoprotein articles), or γ-tocopherol.

CONCLUSIONS

Elevated retinol may be associated with an increased risk of SGA, whereas elevated carotenoid levels may reduce the risk. A better understanding of the nature of these associations is required, however, before recommending specific nutritional interventions in an attempt to prevent SGA birth.

Association between vitamin B12intake and EURRECA's prioritized biomarkers of vitamin B12in young populations: a systematic review

Objective

To review evidence on the associations between vitamin B12intake and its biomarkers, vitamin B12intake and its functional health outcomes, and vitamin B12biomarkers and functional health outcomes.

Design

A systematic review was conducted by searching electronic databases, until January 2012, using a standardized strategy developed in the EURRECA network. Relevant articles were screened and sorted based on title and abstract, then based on full text, and finally included if they met inclusion criteria. A total of sixteen articles were included in the review.

Setting

Articles covered four continents: America (n4), Europe (n8), Africa (n1) and Asia (n3).

Subjects

Population groups included healthy infants, children and adolescents, and pregnant and lactating women.

Results

From the total number of 5815 papers retrieved from the initial search, only sixteen were eligible according to the inclusion criteria: five for infants, five for children and adolescents, and six for pregnant and lactating women.

Conclusions

Only one main conclusion could be extracted from this scarce number of references: a positive association between vitamin B12intake and serum vitamin B12in the infant group. Other associations were not reported in the eligible papers or the results were not provided in a consistent manner. The low number of papers that could be included in our systematic review is probably due to the attention that is currently given to research on vitamin B12in elderly people. Our observations in the current systematic review justify the idea of performing well-designed studies on vitamin B12in young populations.

Gaps in the evidence for prevention and treatment of maternal anaemia: a review of systematic reviews

BACKGROUND

Anaemia, in particular due to iron deficiency, is common in pregnancy with associated negative outcomes for mother and infant. However, there is evidence of significant variation in management. The objectives of this review of systematic reviews were to analyse and summarise the evidence base, identify gaps in the evidence and develop a research agenda for this important component of maternity care.

METHODS

Multiple databases were searched, including MEDLINE, EMBASE and The Cochrane Library. All systematic reviews relating to interventions to prevent and treat anaemia in the antenatal and postnatal period were eligible. Two reviewers independently assessed data inclusion, extraction and quality of methodology.

RESULTS

27 reviews were included, all reporting on the prevention and treatment of anaemia in the antenatal (n = 24) and postnatal periods (n = 3). Using AMSTAR as the assessment tool for methodological quality, only 12 of the 27 were rated as high quality reviews. The greatest number of reviews covered antenatal nutritional supplementation for the prevention of anaemia (n = 19). Iron supplementation was the most extensively researched, but with ongoing uncertainty about optimal dose and regimen. Few identified reviews addressed anaemia management post-partum or correlations between laboratory and clinical outcomes, and no reviews reported on clinical symptoms of anaemia.

CONCLUSIONS

The review highlights evidence gaps including the management of anaemia in the postnatal period, screening for anaemia, and optimal interventions for treatment. Research priorities include developing standardised approaches to reporting of laboratory outcomes, and information on clinical outcomes relevant to the experiences of pregnant women.

Prenatal nutrition and birth outcomes

The complex relationship between maternal nutritional and birth outcomes emphasizes the need for consistent and thorough assessments of women's diet throughout pregnancy and individualized nutritional education to promote positive birth outcomes. The purpose of this article is to examine the influence of prenatal nutrition on birth outcomes, describe research on the effects of macro- and micronutrients on birth outcomes, and discuss strategies for monitoring diet and implementing nutrition education during pregnancy.

Intake of micronutrient-rich foods in rural Indian mothers is associated with the size of their babies at birth: Pune Maternal Nutrition Study

One third of the Indian babies are of low birth weight (<2.5 kg), and this is attributed to maternal undernutrition. We therefore examined the relationship between maternal nutrition and birth size in a prospective study of 797 rural Indian women, focusing on macronutrient intakes, dietary quality and micronutrient status. Maternal intakes (24-h recall and food frequency questionnaire) and erythrocyte folate, serum ferritin and vitamin C concentrations were measured at 18 +/- 2 and 28 +/- 2 wk gestation. Mothers were short (151.9 +/- 5.1 cm) and underweight (41.7 +/- 5.1 kg) and had low energy and protein intakes at 18 wk (7.4 +/- 2.1 MJ and 45.4 +/- 14.1 g) and 28 wk (7.0 +/- 2.0 MJ and 43.5 +/- 13.5 g) of gestation. Mean birth weight and length of term babies were also low (2665 +/- 358 g and 47.8 +/- 2.0 cm, respectively). Energy and protein intakes were not associated with birth size, but higher fat intake at wk 18 was associated with neonatal length (P < 0.001), birth weight (P < 0.05) and triceps skinfold thickness (P < 0.05) when adjusted for sex, parity and gestation. However, birth size was strongly associated with the consumption of milk at wk 18 (P < 0.05) and of green leafy vegetables (P < 0.001) and fruits (P < 0.01) at wk 28 of gestation even after adjustment for potentially confounding variables. Erythrocyte folate at 28 wk gestation was positively associated with birth weight (P < 0.001). The lack of association between size at birth and maternal energy and protein intake but strong associations with folate status and with intakes of foods rich in micronutrients suggest that micronutrients may be important limiting factors for fetal growth in this undernourished community.

Nutrient intakes during pregnancy: the influence of smoking status and age

STUDY OBJECTIVE

To examine the relation of antioxidant and other nutrient intakes in pregnancy to smoking and sociodemographic variables.

DESIGN

Cohort study.

SETTING

St Mary's Maternity Hospital, Portsmouth.

PARTICIPANTS

Pregnant nulliparous women, with no existing complications of pregnancy, were recruited from antenatal booking clinics. A total of 774 women completed seven day food diaries, and supplied detailed data on their use of nutrient supplements.

MAIN RESULTS

Smokers had lower intakes of most micronutrients. After adjustment for the confounding effects of maternal age, height, and education, only vitamin C and carotenoid intakes remained significantly depressed. Age was strongly and significantly associated with the intake of most nutrients, including antioxidants, and this association was independent of other maternal factors. Antioxidant intake was therefore lowest in young women who smoked: for example smokers under 24 years had a mean vitamin C intake of 57 mg (SD 35) compared with 106 mg (SD 52) for non-smokers aged 28 and over (difference 49 mg, 95% CI 39, 59). The corresponding intakes of carotenoid equivalents were 1335 micrograms (SD 982) and 2093 micrograms (SD 1283) (difference 758 micrograms, 95% CI 496, 1020).

CONCLUSIONS

The study has identified, for the first time, young pregnant women as a group at particular risk of low micronutrient intake. The health implications of poor nutrition now need to be evaluated, particularly for those women who smoke.

Influence of maternal nutrition on outcome of pregnancy: prospective cohort study

OBJECTIVE

To investigate the relations of maternal diet and smoking during pregnancy to placental and birth weights at term.

DESIGN

Prospective cohort study.

SETTING

District general hospital in the south of England.

PARTICIPANTS

693 pregnant nulliparous white women with singleton pregnancies who were selected from antenatal booking clinics with stratified random sampling.

MAIN OUTCOME MEASURES

Birth and placental weights at term.

RESULTS

Placental and birth weights were unrelated to the intake of any macronutrient. Early in pregnancy, vitamin C was the only micronutrient independently associated with birth weight after adjustment for maternal height and smoking. Each ln mg increase in vitamin C was associated with a 50.8 g (95% confidence interval 4.6 g to 97.0 g) increase in birth weight. Vitamin C, vitamin E, and folate were each associated with placental weight after adjustment for maternal characteristics. In simultaneous regression, however, vitamin C was the only nutrient predictive of placental weight: each ln mg increase in vitamin C was associated with a 3.2% (0.4 to 6.1) rise in placental weight. No nutrient late in pregnancy was associated with either placental or birth weight.

CONCLUSIONS

Concern over the impact of maternal nutrition on the health of the infant has been premature. Maternal nutrition, at least in industrialised populations, seems to have only a small effect on placental and birth weights. Other possible determinants of fetal and placental growth should be investigated.