The relationship between maternal serum zinc levels during pregnancy and birthweight

Association Between Iron, Folate, and Zinc Deficiencies During Pregnancy and Low Birth Weight: Systematic Review of Cohort Studies

CONTEXT

Iron, folate, and zinc deficiencies during the gestational period may be associated with negative perinatal outcomes, such as low birth weight (LBW), but these relationships are not yet fully established in the scientific literature and require further investigation.

OBJECTIVE

To systematically review the scientific production to investigate the association between iron, folate, and zinc deficiencies during pregnancy and LBW.

DATA SOURCES

The search was carried out using high-sensitivity descriptors in the English, Portuguese, and Spanish languages, combined with Boolean operators, adapted to each of the following indexed databases: MEDLINE via PubMed, Embase, LILACS via BVS, CENTRAL, and Web of Science. The eligibility criteria followed the PECOS (population, exposure, comparator, outcome, study) strategy.

DATA EXTRACTION

Data extraction was performed using an Excel spreadsheet with the study variables of interest. Subsequently, the information was analyzed and summarized in a table. The Newcastle-Ottawa Scale was used to perform the risk-of-bias analysis.

DATA ANALYSIS

A total of 21 042 references were identified, of which 7169 related to folate, 6969 to iron, and 6904 to zinc. After eligibility criteria application, 37 articles were included in this study, of which 18 referred to zinc nutritional status, 10 related to iron, and 9 related to folate. Studies of iron (40%), folate (66.66%), and zinc (50%) revealed a positive association between deficiencies of these micronutrients and LBW. The overall methodological quality of the studies included in this review was considered high.

CONCLUSIONS

Iron, folate, and zinc deficiencies are still present during gestation. Nevertheless, the association between deficiencies of these micronutrients and LBW is still contradictory, and more studies are needed, as is efficient nutritional monitoring before and during gestation.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021284683.

Maternal Nutrition and Fetal/Infant Development

Nutrition in pregnant mothers has long been known to be an important determinant of fetal/maternal outcomes. In general, the typical American diet shows opportunities for improvement. The intake of fruits, vegetables, whole grains, and fiber may be below recommended levels, but the relative proportion of sodium, fats, and carbohydrates seems high. In this review, we present current evidence on how the fetal/neonatal outcomes may be altered by maternal nutrition at the time of conception, fetal nutrition in utero, contribution of maternal dietary factors in fetal outcomes, weight gain during pregnancy, diabetes during pregnancy, fetal growth restriction (FGR), maternal nutritional status during later pregnancy, and pregnancy in adolescent mothers.

Association of selenium, zinc and copper concentrations during pregnancy with birth weight: A systematic review and meta-analysis

BACKGROUND

Normal fetal growth is associated with maternal nutrition. Trace elements play important roles in fetus growth. This review aims to provide a summary of the literature evaluating the relation between selenium, zinc and copper levels during pregnancy with birth weight.

METHOD

A systematic literature search was conducted in Medline database (PubMed), Scopus, Web of science and Google scholar up to September 2020. Fifty observational studies were included in the final analyses. The desired pooled effect size was considered as standardized mean differences with 95 % CI or correlation. Cochran's Q statistic was used to test the heterogeneity between the included studies (I²).

RESULT

A significant differences were found between pooled standardized mean differences (SMD) of umbilical cord blood copper levels in small-for-gestational age birth weight (SGA) and appropriate-for-gestational age birth weight (AGA) (SMD: 0.34 μg/L, 95 % CI: 0.13 to 0.56). There was a significant pooled correlation between umbilical cord blood selenium concentrations and birth weight (r: 0.08, 95 % CI: 0.01 to 0.16). A significant pooled correlation was found between umbilical cord blood zinc concentrations and birth weight (r: 0.09, 95 % CI: 0.04 to 0.15), with significant heterogeneity (I² % = 0.63). There was significant positive association between maternal blood zinc concentrations and birth weight.

CONCLUSION

Findings showed the association of trace elements including selenium, zinc and copper during pregnancy with birth weight. There was significant correlation between umbilical cord and maternal blood selenium and zinc levels with birth weight. The umbilical cord blood copper levels in SGA birth weight was higher than copper levels in AGA birth weight.

Zinc and copper levels in low birth weight deliveries in Medani Hospital, Sudan

Background

Low birth weight (LBW) is a worldwide health problem, especially in developing countries. We conducted a case–control study at Medani Hospital, Sudan. Cases were women who delivered a LBW (<2500 g) newborn and consecutive women who delivered a normal weight (>2500 g) newborn were controls. Questionnaires were used to collect clinical data. Zinc and copper levels were measured by an atomic absorption spectrophotometer.

Findings

The two groups (50 in each arm) were well matched in their basic characteristics. Median (25–75th interquartile range) maternal zinc (62.9 [36.3–96.8] vs. 96.2 [84.6–125.7] μg/dl; P <0.001) and copper (81.6 [23.7–167.5] vs. 139.8 [31.9–186.2] μg/dl; P = 0.04) levels were significantly lower in cases than in controls. Cord copper levels in cases were significantly lower than those in controls (108 [55.1–157.9] vs. 147.5 [84.5–185.2] μg/dl; P = 0.02). There were significant direct correlations between birth weight and maternal copper levels and maternal and cord zinc levels.

Conclusions

Maternal zinc and copper levels, as well as cord copper levels, are lower in LBW newborns than in those with normal weight.

Does lack of multinutrient supplementation during early pregnancy increase vulnerability to alcohol-related preterm or small-for-gestational-age births?

The objective of this study was to assess whether women who do not take multinutrient supplements during early pregnancy are more susceptible to the effects of low-to-moderate alcohol consumption on preterm birth and small-for-gestational-age birth (SGA) compared to women who do take multinutrients. This analysis included 800 singleton live births to mothers from a cohort of pregnant women recruited for a population-based cohort study conducted in the Kaiser Permanente Medical Care Program in Northern California. Participants were recruited in their first trimester of pregnancy and information about their alcohol use and supplement intake during pregnancy was collected. Preterm birth (n = 53, 7%) was defined as a delivery prior to 37 completed weeks of gestation and SGA birth (n = 124, 16%) was defined as birth weight less than the 10th percentile for the infant’s gestational age and sex compared to US singleton live births. A twofold increase in the odds of SGA birth attributed to low-to-moderate alcohol intake was found among multinutrient supplement non-users (95% CI: 1.1, 5.3). Yet, among multinutrient supplement users, there was no increased risk of an SGA birth for women who drank low-to-moderately compared to women who abstained (aOR: 0.97, 95% CI: 0.6, 1.6). Similar results emerged for preterm birth. Our findings provide marginal evidence that multinutrient supplementation during early pregnancy may modify the risk of SGA births and preterm birth associated with alcohol consumption during pregnancy and may have important implications for pregnant women and women of child-bearing age. However, future research needs to be conducted.

Impact of maternal zinc status on fetal growth in an Iranian pregnant population

BACKGROUND

To evaluate the impact of mild to moderate maternal zinc deficiency on birth weight of offsprings in a group of Iranian pregnant population.

MATERIALS AND METHODS

One hundred forty pregnant subjects with no history of medical complications during pregnancy and without any inter-current illness enrolled in the study. Serum zinc concentration, ferritin, hemoglobin, iron, and total iron binding capacity (TIBC) were measured at the time of delivery. The receiver operator characteristic (ROC) curve analysis used to determine plasma zinc cutoff value for comparison.

RESULTS

Of 140 live neonates, 30% were below 2500 g. Mean serum zinc concentration was 56.60 ± 17.91 μg/dl which indicated mild to moderate zinc deficiency. None of the subjects were anemic. There was an inverse statistically significant relationship between maternal serum zinc concentration and neonatal birth weight.

CONCLUSION

In this group of Iranian pregnant subjects with mild to moderate zinc deficiency, we observed no relationship between low maternal zinc status and low birth weight infants.

The plausibility of maternal nutritional status being a contributing factor to the risk for fetal alcohol spectrum disorders: the potential influence of zinc status as an example

There is increasing evidence that human pregnancy outcome can be significantly compromised by suboptimal maternal nutritional status. Poor diet results in a maternal-fetal environment in which the teratogenicity of other insults such as alcohol might be amplified. As an example, there is evidence that zinc (Zn) can interact with maternal alcohol exposure to influence the risk for fetal alcohol spectrum disorders (FASD). Studies with experimental animals have shown that the teratogenicity of alcohol is increased under conditions of Zn deficiency, whereas its teratogenicity is lessened when animals are given Zn-supplemented diets or Zn injections before the alcohol exposure. Alcohol can precipitate an acute-phase response, resulting in a subsequent increase in maternal liver metallothionein, which can sequester Zn and lead to decreased Zn transfer to the fetus. Importantly, the teratogenicity of acute alcohol exposure is reduced in metallothionein knockout mice, which can have improved Zn transfer to the conceptus relative to wild-type mice. Consistent with the above, Zn status has been reported to be low in alcoholic women at delivery. Preliminary data from two basic science and clinical nutritional studies that are ongoing as part of the international Collaborative Initiative on Fetal Alcohol Spectrum Disorders support the potential role of Zn, among other nutritional factors, relative to risk for FASD. Importantly, the nutrient levels being examined in these studies are relevant to general clinical populations and represent suboptimal levels rather than severe deficiencies. These data suggest that moderate deficiencies in single nutrients can act as permissive factors for FASD, and that adequate nutritional status or intervention through supplementation may provide protection from some of the adverse effects of prenatal alcohol exposure.

Do multivitamin supplements modify the relationship between prenatal alcohol intake and miscarriage?

OBJECTIVE

To determine whether multivitamin supplements modify the relationship between alcohol consumption during pregnancy and the risk of miscarriage.

STUDY DESIGN

We used data from a population-based cohort study of pregnant women (n=1061; response rate=39%). Participants were asked about their alcohol consumption and vitamin intake during pregnancy.

RESULTS

Among multivitamin nonusers, women who drank alcohol during their pregnancy were more likely to have a miscarriage compared with women who abstained (adjusted hazard ratio, 1.67; 95% confidence interval, 1.04-2.69). However, among multivitamin users, there was no difference in the risk of miscarriage between alcohol consumers and abstainers. Results suggest the volume of alcohol as well as the timing of multivitamin supplementation may also be important.

CONCLUSION

Our findings suggest that a woman of childbearing years might decrease her risk of miscarriage associated with alcohol intake by taking multivitamin supplements. However, our findings should be interpreted with caution and future research replicating these findings is necessary.

Uteroplacental insufficiency affects epigenetic determinants of chromatin structure in brains of neonatal and juvenile IUGR rats

Intrauterine growth retardation (IUGR) increases the risk of neuroendocrine reprogramming. In the rat, IUGR leads to persistent changes in cerebral mRNA levels. This suggests lasting alterations in IUGR cerebral transcriptional regulation, which may result from changes in chromatin structure. Candidate nutritional triggers for these changes include altered cerebral zinc and one-carbon metabolite levels. We hypothesized that IUGR affects cerebral chromatin structure in neonatal and postnatal rat brains. Rats were rendered IUGR by bilateral uterine artery ligation; controls (Con) underwent sham surgery. At day of life 0 (d0), we measured cerebral DNA methylation, histone acetylation, expression of chromatin-affecting enzymes, and cerebral levels of one-carbon metabolites and zinc. At day of life 21 (d21), we measured cerebral DNA methylation and histone acetylation, as well as the caloric content of Con and IUGR rat breast milk. At d0, IUGR significantly decreased genome-wide and CpG island methylation, as well as increased histone 3 lysine 9 (H3/K9) and histone 3 lysine 14 (H3/K14) acetylation in the hippocampus and periventricular white matter, respectively. IUGR also decreased expression of the chromatin-affecting enzymes DNA methyltransferase 1 (DNMT1), methyl-CpG binding protein 2 (MeCP2), and histone deacetylase (HDAC)1 in association with increased cerebral levels of zinc. In d21 female IUGR rats, cerebral CpG DNA methylation remained lower, whereas H3/K9 and H3/K14 hyperacetylation persisted in hippocampus and white matter, respectively. In d21 male rats, IUGR decreased acetylation of H3/K9 and H3/K14 in these respective regions compared with controls. Despite these differences, caloric, fat, and protein content were similar in breast milk from Con and IUGR dams. We conclude that IUGR results in postnatal changes in cerebral chromatin structure and that these changes are sex specific.

The plausibility of micronutrient deficiencies being a significant contributing factor to the occurrence of pregnancy complications

Numerous studies support the concept that a major cause of pregnancy complications can be suboptimal embryonic and fetal nutrition. Although the negative effects of diets low in energy on pregnancy outcome are well documented, less clear are the effects of diets that are low in one or more essential micronutrients. However, several observational and intervention studies suggest that diets low in essential vitamins and minerals can pose a significant reproductive risk in diverse human populations. Although maternal nutritional deficiencies typically occur as a result of low dietary intakes of essential nutrients, nutritional deficiencies at the level of the conceptus can arise through multiple mechanisms. Evidence from experimental animals supports the concept that in addition to primary deficiencies, secondary embryonic and fetal nutritional deficiencies can be caused by diverse factors including genetics, maternal disease, toxicant insults and physiological stressors that can trigger a maternal acute phase response. These secondary responses may be significant contributors to the occurrence of birth defects. An implication of the above is that the frequency and severity of pregnancy complications may be reduced through an improvement in the micronutrient status of the mother.

Growth, development and differentiation: a functional food science approach

Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behaviour, a phenomenon called 'metabolic programming'. The interaction of nutrients and gene expression may form the basis of many of these programming effects and needs to be investigated in more detail. The relation between availability of food ingredients and cell and tissue differentiation and its possible uses for promoting health and development requires further exploration. The course of pregnancy, childbirth and lactation as well as human milk composition and the short- and long-term outcome of the child are influenced by the intake of foods and particularly micronutrients, e.g. polyunsaturated fatty acids, Fe, Zn and I. Folic acid supplementation from before conception through the first weeks of pregnancy can markedly reduce the occurrence of severe embryonic malformations; other potential benefits of modulating nutrient supply on maternal and child health should be further evaluated. The evaluation of dietary effects on child growth requires epidemiological and field studies as well as evaluation of specific cell and tissue growth. Novel substrates, growth factors and conditionally essential nutrients (e.g. growth factors, amino acids, polyunsaturated fatty acids) may be potentially useful as ingredients in functional foods and need to be assessed carefully. Intestinal growth, maturation, and adaptation as well as long-term function may be influenced by food ingredients such as oligosaccharides, gangliosides, high-molecular-mass glycoproteins, bile salt-activated lipase, pre- and probiotics. There are indications for some beneficial effects of functional foods on the developing immune response, for example induced by antioxidant vitamins, trace elements, fatty acids, arginine, nucleotides, and altered antigen contents in infant foods. Peak bone mass at the end of adolescence can be increased by dietary means, which is expected to be of long-term importance for the prevention of osteoporosis at older ages. Future studies should be directed to the combined effects of Ca and other constituents of growing bone, such as P, Mg and Zn, as well as vitamins D and K, and the trace elements F and B. Pregnancy and the first postnatal months are critical time periods for the growth and development of the human nervous system, processes for which adequate substrate supplies are essential. Early diet seems to have long-term effects on sensory and cognitive abilities as well as behaviour. The potential beneficial effects of a balanced supply of nutrients such as I, Fe, Zn and polyunsaturated fatty acids should be further evaluated. Possible long-term effects of early exposure to tastes and flavours on later food choice preferences may have a major impact on public health and need to be further elucidated. The use of biotechnology and recombinant techniques may offer the opportunity to include various bioactive substances in special dietary products, such as human milk proteins, peptides, growth factors, which may have beneficial physiological effects, particularly in infancy and early childhood.

Zinc and copper concentrations in serum from Spanish women during pregnancy

A cross-sectional study of serum zinc (Zn) and copper (Cu) levels in 31 healthy pregnant women and 51 healthy, nonpregnant controls living in the Mediterranean area of Granada, Spain, was performed. The subjects were divided into two groups: Group A, consisted of pregnant women in three categories according to the trimester of pregnancy, and Group B consisted of nonpregnant women acting as controls. In pregnant women, serum Zn levels were found from 0.300-1.340 mg/L and serum Cu from 0.936-2.304 mg/L, whereas in the nonpregnant women group, the mean serum levels were 0.947+/-0.265 mg/L for Zn and 1.092+/-0.365 mg/L for Cu. Serum Zn progressively decreased with gestation. Mean Zn levels were 0.829+/-0.253, 0.846+/-0.329, and 0.620+/-0.142 mg/L, corresponding to the first, second, and third trimesters of pregnancy, respectively. Serum Zn concentrations were significantly lower in pregnant women as compared to controls: 0.712+/-0.236 mg/L vs 0.947+/-0.265 mg/L, respectively (p < 0.05). In contrast, Cu levels increased with period of gestation from 1.053+/-0.498 mg/L in the first trimester to 1.616+/-0.304 mg/L in the second and 1.689+/-0.344 mg/L in the third. Serum Cu levels in the second and third trimesters of pregnancy were significantly higher (p < 0.05) than those determined during the first trimester and for nonpregnant controls. Both Zn and Cu during pregnancy did not appear to be dependent on the subject's age (p > 0.05).

Toxicant exposure and trace element metabolism in pregnancy

A review of the literature provides support for the concept that maternal nutritional status has a significant influence on embryonic and fetal development. The consumption of `poor' diets has been shown to be a risk factor for poor pregnancy outcome, while the provision of selected nutritional supplements prior to and during pregnancy has been associated with improved pregnancy outcome. Despite the above, it has been difficult to identify specific nutrient deficiencies as causative factors of abnormal development. One explanation for this failure is that embryo/fetal nutritional deficiencies can arise through a number of mechanisms in addition to a low maternal intake of a nutrient(s). Evidence is presented for the hypothesis that the developmental toxicity of a number of teratogens can be ascribed, in part, to their ability to induce alterations in the partitioning of essential trace elements between the maternal and fetal unit. An implication of the above hypothesis is that maternal diet can be an important modulator of the developmental toxicity of several agents.

Maternal nutrition and obstetric outcome

In general, maternal nutritional status in civilized countries is not at risk. However, even a marginal malnutritional state for some (micro)nutrients for the pregnant women can adversely affect obstetrical outcome. From the data available so far, only folic acid supplementation is advised. However, the importance of an adequate iron and zinc status has to be stressed. In addition, women should be warned preconceptionally about excessive intake of vitamins, especially of those products containing large amounts of vitamin A.

Vitamin A and related essential nutrients in cord blood: relationships with anthropometric measurements at birth

Following the advice given by the Department of Health to women who are, or may become pregnant, not to eat liver and liver products because of the risk of vitamin A toxicity, the concentrations of vitamins A and E, and copper, magnesium and zinc in cord blood were investigated. The study was conducted in Hackney, an inner city area of London. Esters of vitamin A were not detected in any of the samples, indicating that there was no biochemical evidence of a risk of toxicity. Indeed, vitamin A correlated significantly with birthweight, head circumference, length, and gestation period. There was also a significant positive relationship between zinc and birthweight. In contrast, copper showed a negative correlation with birthweight and head circumference. Vitamin E and magnesium were not associated with any of the anthropometric measurements, although magnesium showed an increasing trend with birthweight. The data suggest that most of the mothers of the subjects studied may have been marginal with respect to vitamins A and E and zinc. In those with low birthweight babies. a higher intake would have improved their nutritional status and possibly the outcome of their pregnancy. For these low-income mothers, liver and liver products are the cheapest and the best source of vitamins A and E, haem iron, B vitamins and several other essential nutrients; hence the advice of the Department of Health may have been misplaced.

Zinc status of a group of pregnant adolescents at 36 weeks gestation living in southern Ontario

OBJECTIVE

Pregnant adolescents have very high zinc (Zn) requirements to support the developing fetus and to maintain skeletal maturation after menarche.

METHODS

Sixty-six adolescents aged 17.1 +/- 0.15 years (mean +/- SEM; range 14.5-19.0 years) were recruited from three regions of Southern Ontario at 35.9 +/- 0.15 weeks gestation. Data on sociodemographic status, health, infant birth weight and birth length, smoking, alcohol consumption, and prenatal supplement use were collected. Fasting venipuncture blood was analyzed for Zn (via AAS) and alkaline phosphatase in plasma; scalp hair was analyzed for Zn by instrumental neutron activation.

RESULTS

Mean (95% CI) values were: plasma Zn 10.7 (10.0-11.5) mumol/L; plasma alkaline phosphatase 46.6 (43.7-49.5) U/L; hair Zn 2.64 (2.52-2.77) mumol/g. None of the plasma and hair Zn values were indicative of suboptimal Zn status. Mean plasma Zn concentrations of subjects (n = 19) consuming a supplement with Zn sulfate were higher than those of subjects consuming a supplement with Zn oxide (n = 18) (12.2 vs 9.7 mumol/L; p < 0.02) and unsupplemented subjects (n = 11) (9.4 mumol/L). Plasma Zn concentrations correlated negatively with reported birth lengths (mean +/- SEM = 51.6 +/- 0.31 cm) while accounting for chronological age (r = 0.42; p < 0.01), but not with reported birth weights (mean +/- SEM = 3.439 +/- 0.107 kg).

CONCLUSIONS

Results emphasize that the form of Zn must be taken into account when considering the impact of prenatal supplements containing Zn on plasma Zn concentrations. Suboptimal Zn status was not prevalent in these pregnant adolescents.

Maternal alpha-2-macroglobulin levels and fetal growth in Guatemala

Maternal serum alpha-2-macroglobulin (alpha 2M) levels were measured at the time of delivery in 244 women in the central highlands of Guatemala. Significantly higher alpha 2M levels were found in thin women and in poor women. In multiple regression analysis controlling for gestational age, race, sex, maternal triceps skinfold thickness and socioeconomic status, high alpha 2M levels were significantly associated with decreased birthweight. These findings agree with those in a predominantly black population in the United States and extend the relationship between alpha 2M and decreased birthweight to a developing country.