Plasma and erythrocyte zinc and birth weight in pre-eclamptic pregnancies

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.

Profile of trace element concentrations in the feto-placental unit in relation to fetal growth

BACKGROUND

During pregnancy, trace elements are indispensable for life maintenance not only for the mother but also for the fetus. The purpose of this study was to examine whether fetal growth is associated with altered levels of trace elements in maternal blood, fetal blood, and placenta tissue.

METHODS

Twenty-one pairs of healthy mothers and their newborns with intrauterine growth restriction delivered after 34 weeks of gestation were recruited for the study. In addition, 30 pairs of healthy mothers and their appropriate for gestational age newborns were included as controls. Maternal venous blood, umbilical cord venous and arterial blood, and placenta tissue were collected immediately after delivery. Six essential elements, magnesium, manganese, iron, copper, zinc, and selenium, and four other elements, rubidium, strontium, cadmium, and cesium, in those samples were determined by inductively coupled plasma mass spectrometry or inductively coupled plasma atomic emission spectrometry.

RESULTS

Compared with appropriate for gestational age cases, intrauterine growth restriction cases showed higher magnesium, copper, and selenium concentrations in umbilical cord arterial sera, and higher magnesium and selenium concentrations in placenta tissue, but no significant differences appeared for the elements measured in maternal and umbilical cord venous sera. The umbilical cord venous vs. maternal sera concentration ratio was elevated for copper, and the umbilical cord arterial vs. umbilical cord venous sera concentration ratios were elevated for copper and zinc, but there were no differences in placenta tissue vs. maternal sera concentration ratios in intrauterine growth restriction cases.

CONCLUSIONS

Among the trace elements evaluated, magnesium, copper, zinc, and selenium showed elevated concentrations in umbilical cord arterial blood, or elevated umbilical cord arterial vs. umbilical cord venous blood concentration ratios in intrauterine growth restriction cases. Reduced consumption efficiency of these four essential trace elements may be closely associated with retarded fetal development.

Effect of gestational zinc deficiency on pregnancy outcomes: summary of observation studies and zinc supplementation trials

The lack of a valid indicator precludes a true estimate of zinc deficiency in pregnancy in various populations. However, it is possible that mild to moderate deficiency (as assessed by available indicators) may be common in the developing world. Animal experiments indicate that zinc deficiency can result in adverse maternal and fetal consequences. Human data, particularly from prenatal zinc supplementation trials, has failed to document a consistent maternal or infant benefit on evaluated outcome measures including pregnancy induced hypertension, preterm/post-term labour, premature rupture of membranes, maternal infection, postpartum haemorrhage, perinatal mortality, congenital malformations and fetal growth and gestation. Preliminary data suggest a beneficial effect of prenatal zinc supplementation on infants' neurobehavioural development and immune function (evaluated by diarrhoeal and ARI morbidity incidence in the first year of life). Future research should focus on these functional consequences and congenital malformations (with adequate sample sizes), and simultaneously address the safety issue, particularly in relation to micronutrient interactions. In the light of the currently available information, routine zinc supplementation can not be advocated to improve pregnancy outcome.

Maternal plasma zinc concentrations and pregnancy outcome

BACKGROUND

There is no consensus in the literature as to whether maternal zinc nutriture is associated with pregnancy outcome or fetal growth.

OBJECTIVE

We evaluated the associations between plasma zinc concentrations during pregnancy and various measures of pregnancy outcome and neonatal conditions at birth.

DESIGN

We measured zinc concentrations in plasma samples obtained at a mean of 16 wk of gestation (range: 6-34 wk) from 3448 women who were screened for a trial designed to evaluate the effect of zinc supplementation on fetal growth. Subjects were from low socioeconomic backgrounds and attended a public health clinic for their prenatal care. Plasma zinc concentrations were compared with pregnancy outcome, including complications during pregnancy and delivery, and anthropometric measures and Apgar scores of neonates.

RESULTS

Plasma zinc concentrations declined as gestation progressed. After plasma zinc concentrations were adjusted for gestational age, they were not significantly associated with any measure of pregnancy outcome or neonatal condition.

CONCLUSION

We conclude that plasma zinc concentrations during the late first trimester to the early third trimester do not predict pregnancy outcomes in women of a low socioeconomic background.