Zinc deficiency is not a cause for abortion, congenital abnormality and small-for-gestational age infant in Chinese women

Association between female circulating heavy metal concentration and abortion: a systematic review and meta-analysis

Objective

This study aimed to evaluate the association between blood heavy metal (zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd)) concentrations and spontaneous abortion (SA) and recurrent pregnancy loss (RPL) and explore the possible endocrine dysfunction associated with it.

Methods

A literature search was performed in the PubMed, Embase, Cochrane Library, and Web of Science databases up to April 2023. The overall effects were expressed as the standard mean difference (SMD). Subgroup analysis was performed according to the type of abortion (SA or RPL). Stata 16.0 was utilized for data analysis.

Results

Based on the integrated findings, abortion women showed significantly lower Zn (SMD = -1.05, 95% CI: -1.74 to -0.36, p = 0.003) and Cu concentrations (SMD = -1.42, 95% CI: -1.97 to -0.87, p <0.001) and higher Pb (SMD = 1.47, 95% CI: 0.89-2.05, p <0.001) and Cd concentrations (SMD = 1.15, 95% CI: 0.45-1.85, p = 0.001) than normal pregnant women. Subgroup analysis showed that Zn and Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with RPL, whereas Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with SA.

Conclusion

Zn and Cu deficiencies and Pb and Cd exposure were associated with abortion. Endocrine dysfunction, such as insulin resistance, vitamin D insufficiency, and abnormal thyroid and sex hormone concentrations, is thought to be involved in heavy metal-related abortion.

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.

Maternal serum zinc concentration and neural tube defects in offspring: a meta-analysis

OBJECTIVE

This study was to assess the relationship between maternal serum zinc concentration and NTDs in offspring by conducting a meta-analysis.

METHODS

We searched Pubmed, Medline and Web of Science for all English studies about the relationship between maternal serum zinc level and NTDs in offspring (published between 1 January 1975 and 1 January 2020). Pooled effect sizes with corresponding 95% CIs were calculated using a random-effect model by Revman 5.3 and Stata 15.1 software.

RESULTS

Eight articles met our selection criteria and a total of 187 cases and 894 controls were included in this meta-analysis. Our results showed that mothers with NTDs infants had lower serum zinc concentration than those with healthy infants (SMD= -0.77, 95%CI [-1.16, -0.37], p = .0001, I ² = 73%).

CONCLUSIONS

Compared with mothers with healthy infants, mothers with NTDs infants have lower serum zinc levels, suggesting that low maternal serum zinc level during pregnancy is probably associated with the risk of NTDs in offspring. But the mechanism of the association remains to be ascertained by large-scale cohort studies.

Zinc Levels and Birth Weight in Pregnant Women with Gestational Diabetes Mellitus: A Matched Cohort Study in China

BACKGROUND

Zinc (Zn) has been suggested to impact fetal growth. However, the effect may be complicated by gestational diabetes mellitus (GDM) due to its impact on fetal growth and placental transport. This study aims to investigate whether GDM modifies the association between Zn levels and birth weight.

METHOD

A cohort matched by GDM was established in Taiyuan, China, between 2012 and 2016, including 752 women with GDM and 744 women without. Dietary Zn intake was assessed during pregnancy. Maternal blood (MB) and cord blood (CB) Zn levels were measured at birth. Birth weight was standardized as the z score and categorized as high (HBW, >4000 g) and low (LBW, <2500 g) groups. Multivariate linear regression and multinomial logistic regression were used to examine the association between Zn levels and birth weight in offspring born to women with or without GDM.

RESULTS

88.8% (N = 1328) of the population had inadequate Zn intake during pregnancy. In women with GDM, MB Zn level was inversely associated with birth weight (β = -.17; 95% confidence interval (CI), -0.34 to -0.01), while CB Zn level was positively associated with birth weight (β = .38; 95% CI, 0.06-0.70); suggestive associations were observed between MB Zn level and LBW (odds ratio 2.01; 95% CI, 0.95-4.24) and between CB Zn level and HBW (odds ratio 2.37; 95% CI, 1.08-5.21).

CONCLUSIONS

GDM may modify the associations between MB and CB Zn levels and birth weight in this population characterized by insufficient Zn intake. These findings suggest a previously unidentified path of adverse effects of GDM.

Magnitude of Zinc Deficiency among Nulliparous Nonpregnant Women in a Rural Community of Haryana State, India

Zinc deficiency during pregnancy affects the outcome of pregnancy. A high prevalence of zinc deficiency (55.5%) has been reported among pregnant women. It is not known whether pregnancy leads to zinc deficiency due to the increased fetal needs or whether the women are zinc deficient when they become pregnant. No data are available on the zinc status of nulliparous nonpregnant women from India. To assess the magnitude of zinc deficiency among nulliparous nonpregnant women in a rural community of Haryana State, India. A community-based cross-sectional survey was conducted in six villages of a rural area in a district of Haryana State, India. All nulliparous nonpregnant women aged 18 years or over who were willing to participate in the study were enrolled. Each woman was questioned about her age, socioeconomic status, and dietary pattern with the use of a pretested semistructured questionnaire. Blood from the antecubital vein was drawn to assess the serum zinc levels using an atomic absorption spectrophotometer. Serum zinc levels less than 70.0 μg/dl were considered to indicate zinc deficiency. The dietary intakes of zinc, protein, and calories were assessed by the 24-hour dietary recall method. Two hundred eighty-eight nulliparous nonpregnant women were enrolled. Forty-one percent had zinc deficiency, and 75.7%, 1.4%, and 7.3% of the women consumed less than 50% of the recommended intake of zinc, protein, and calories, respectively. Women who consumed less than 50% of the recommended intake of calories (1,875 kcal) were at a 4.9 times higher risk of zinc deficiency than women who consumed more than 50% of the recommended intake. A high prevalence of zinc deficiency was found among the nulliparous nonpregnant women in the area studied.

Association between Maternal Zinc Status, Dietary Zinc Intake and Pregnancy Complications: A Systematic Review

Adequate zinc stores in the body are extremely important during periods of accelerated growth. However, zinc deficiency is common in developing countries and low maternal circulating zinc concentrations have previously been associated with pregnancy complications. We reviewed current literature assessing circulating zinc and dietary zinc intake during pregnancy and the associations with preeclampsia (PE); spontaneous preterm birth (sPTB); low birthweight (LBW); and gestational diabetes (GDM). Searches of MEDLINE; CINAHL and Scopus databases identified 639 articles and 64 studies were reviewed. In 10 out of 16 studies a difference was reported with respect to circulating zinc between women who gave birth to a LBW infant (≤2500 g) and those who gave birth to an infant of adequate weight (>2500 g), particularly in populations where inadequate zinc intake is prevalent. In 16 of our 33 studies an association was found between hypertensive disorders of pregnancy and circulating zinc; particularly in women with severe PE (blood pressure ≥160/110 mmHg). No association between maternal zinc status and sPTB or GDM was seen; however; direct comparisons between the studies was difficult. Furthermore; only a small number of studies were based on women from populations where there is a high risk of zinc deficiency. Therefore; the link between maternal zinc status and pregnancy success in these populations cannot be established. Future studies should focus on those vulnerable to zinc deficiency and include dietary zinc intake as a measure of zinc status.

Myo-inositol, glucose and zinc concentrations determined in the preconceptional period, during and after pregnancy

OBJECTIVE

To determine the blood concentrations of myo-inositol, glucose and zinc before, during and after normal pregnancy.

STUDY DESIGN

Preconceptionally, at 6, 10, 20, 30 and 37 weeks amenorrhea, and 6 weeks after delivery, blood samples of 18 nulliparae and 19 multiparae were obtained and concentrations of serum inositol and glucose, and red blood cell zinc were determined. The data were analyzed using a linear mixed model.

RESULTS

The preconceptional mean (S.E.M.) inositol concentration of 21.7 (1.03) micromol/L was comparable to the concentrations at 6 and 37 weeks amenorrhea, 22.2 (1.03) micromol/L, and 19.9 (1.10) micromol/L, respectively. However, the inositol concentrations at 10 and 20 weeks amenorrhea and post partum were significantly lower than the preconceptional inositol concentration, p<0.05. The preconceptional mean (S.E.M.) glucose concentration of 3.9 (1.03) mmol/L was comparable to the concentration at 6 and 10 weeks amenorrhea, 3.9 (1.04) mmol/L and 3.8 (1.04) mmol/L respectively. Also at 20, 30 and 37 weeks amenorrhea and after delivery the glucose concentration was significantly lower than the preconceptional glucose concentration, p<0.05. Preconceptional red blood cell zinc concentrations were comparable to concentrations at 6, 10 and 20 weeks amenorrhea. At 30 and 37 weeks amenorrhea and post partum the zinc concentrations were significantly higher than in the preconceptional period (p<0.01).

CONCLUSION

The concentrations of inositol, glucose and zinc significantly change during pregnancy. However, the preconceptional blood concentrations reflect the concentrations determined in the first pregnancy trimester rather well, which is important information to be used in future studies into the role of inositol, glucose and zinc in reproductive disorders.

Prevalence of multiple micronutrient deficiencies amongst pregnant women in a rural area of Haryana

Deficiencies of micronutrients (zinc, iron, folic acid and iodine) during pregnancy are known causes of Low Birth Weight (LBW). Studies have documented status of one or two micronutrients amongst pregnant women (PW). However, no attempt has been made to concurrently assess the prevalence of multiple micronutrient deficiencies and the factors associated with them amongst PW.

OBJECTIVE

The present study was undertaken to assess the prevalence of multiple micronutrient deficiencies amongst PW in a rural area.

METHODS

A community based cross sectional survey was conducted in six villages of a rural area of district Faridabad in Haryana state, India during November 2000 and October 2001. All PW aged 18 years or more, with pregnancy duration of more than 28 weeks were enrolled. Data were collected on socio-economic status and other demographic parameters. Serum zinc, copper and magnesium levels were estimated by utilizing the Atomic absorption spectrophotometry (AAS); serum ferritin and folate was estimated by Enzyme Linked Immuno Sorbent Assay (ELISA) method and the Radio-Immuno Assay (RIA) method, respectively and serum thyroid stimulating hormone (TSH) level was estimated by the Abbot AxSYM System. Serum zinc, copper, magnesium, ferritin, and folate levels less than 70.0 microg/dl, 80.0 microg/dl, 1.80 mg/dl, 15 ng/ml, and 3 ng/ml, respectively were considered as indicative of deficiency for respective micronutrients. The TSH levels of 4.670 and more indicated iodine deficiency status. Dietary intake of micronutrients was assessed utilizing 1-day 24-hour dietary recall methodology. Food consumption pattern was assessed utilizing the food frequency questionnaire methodology.

RESULTS

Nearly 73.5, 2.7, 43.6, 73.4, 26.3, and 6.4 percent PW were deficient in zinc, copper, magnesium, iron, folic acid and iodine, respectively. The highest concurrent prevalence of two, three, four and five micronutrient deficiency was of zinc and iron (54.9%); zinc, magnesium and iron (25.6%); zinc, magnesium, iron and folic acid (9.3%) and zinc, magnesium, iron, folic acid and iodine (0.8%), respectively. No pregnant woman was found to have concomitant deficiencies of all the six micronutrients. Dietary intake data revealed an inadequate nutrient intake. Over 19% PW were consuming less than 50% of the recommended calories. Similarly, 99, 86.2, 75.4, 23.6, 3.9 percent of the PW were consuming less than 50% of the recommended folic acid, zinc, iron, copper, and magnesium. The consumption of food groups rich in micronutrients (pulses, vegetables, fruits, nuts and oil seeds, animal foods) was infrequent. Univariate and Multivariate logistic regression analysis revealed that low dietary intake of nutrients, low frequency of consumption of food groups rich in micronutrients and increased reproductive cycles with short interpregnancy intervals were important factors leading to micronutrient deficiencies.

CONCLUSION

There was a high prevalence of micronutrient deficiencies amongst the PW of the area, possibly due to the poor dietary intake of food and low frequency of consumption of food groups rich in micronutrients. The concurrent prevalence of two, three, four and five micronutrient deficiencies were common.

Genetic variants in ZIC1, ZIC2, and ZIC3 are not major risk factors for neural tube defects in humans

Neural tube defects (NTD) are congenital malformations arising from incomplete neural tube closure during early embryogenesis. Most NTD in humans show complex inheritance patterns, with both genetic and environmental factors involved in the etiology of this malformation. More than 120 mouse models for human NTD exist. NTD have been observed in mice deficient for the Zic family genes, Zic1, Zic2, and Zic3. We performed mutation analysis in the human orthologs of these genes using DNA material from a large panel of NTD patients. In ZIC2 we identified a deletion of one codon that encodes an alanine residue located in the amino terminal alanine stretch of the protein. The deletion was present in one patient, but not in 364 controls. That may suggest a role-albeit small-of this variant in the etiology of NTD in humans. Transmission disequilibrium testing of a frequent polymorphism in the ZIC2 gene (1059C > T, H353H) in parent-spina bifida aperta child triads showed no association with NTD. One silent polymorphism (858G > A, V286V) of unknown significance was identified in ZIC3. Neither mutations nor polymorphisms were found in the coding region or flanking sequences of ZIC1. Our data indicate that ZIC1, ZIC2, and ZIC3 are not major risk factors for NTD in humans.

Determinants of maternal zinc status during pregnancy

Zinc deficiency in pregnant experimental animals limits fetal growth and, if severe, causes teratogenic anomalies. Although the data from human studies are not consistent, similar outcomes have been observed and were associated with poor maternal zinc status. This paper reviews humans studies of zinc status and pregnancy outcome, describes the physiologic adjustments in zinc utilization during pregnancy to meet fetal needs while maintaining maternal status, and identifies dietary and environmental conditions that may override those physiologic adjustments and put the health of the mother and fetus at risk. Adjustments in intestinal zinc absorption appear to be the primary means by which zinc retention is increased to meet fetal demands. However, transfer of sufficient zinc to the fetus is dependent on maintenance of normal maternal serum zinc concentrations. Conditions that could interfere with zinc absorption include intake of cereal-based diets that are high in phytate, high intakes of supplemental iron, or any gastrointestinal disease. Conditions that may alter maternal plasma zinc concentrations and the transport of zinc to the fetus include smoking, alcohol abuse, and an acute stress response to infection or trauma. Supplemental zinc may be prudent for women with poor gastrointestinal function or with any of these conditions during pregnancy.

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.

Nutritional interventions for the prevention of maternal morbidity

OBJECTIVE

To review the effectiveness of nutritional interventions to prevent maternal morbidity.

METHODS

This is an overview of systematic reviews and individual randomized controlled trials (if no systematic review available) of nutritional interventions during pregnancy. For each nutrient intervention the main maternal morbidity data reported were extracted. These were pre-eclampsia/eclampsia, pregnancy-induced hypertension, hemorrhage, anemia, infection and obstructed labor. In addition, the trial settings, the number of trials and participants' characteristics were systematically extracted.

RESULTS

The systematic reviews considered in this paper had only few trials that reported the selected maternal outcomes. Outcome measures are based sometimes on one trial only. Most of the interventions compared single micronutrient supplementation with placebo/no treatment and did not show significant benefits for the supplementation groups. Calcium supplementation in women at high risk of pregnancy hypertension reduced the incidence of high blood pressure (RR, 0.35; 95% CI, 0.21-0.57) and pre-eclampsia (RR, 0.22; 95% CI, 0.11-0.43). Similarly, in women with low dietary calcium intake, calcium supplementation resulted in a significant reduction in the incidence of high blood pressure (RR, 0.49; 95% CI, 0.38-0.62) and pre-eclampsia (RR, 0.32; CI, 0.21-0.49). In women at low risk of pregnancy hypertension or with adequate baseline calcium intake, the beneficial effects of calcium supplementation are small and unlikely to be of clinical significance. Both, iron and folate supplementation reduced the number of women with low pre-delivery hemoglobin.

CONCLUSIONS

Routine calcium supplementation seems to be a promising intervention for pregnant women at risk of developing preeclampsia or have low calcium intake, but these findings need to be confirmed with a trial with adequate power in different settings. In populations with high incidence of nutritional anemia routine iron and folate supplementation should be recommended during ante-natal care. It is unclear at this stage if adding vitamin A to iron and folate supplementation in anemia prevalent areas provides further benefits. There is inadequate data on the benefits or harms of routine iron or folate supplementation in adequately nourished populations. With regard to other micronutrient supplementation, such as zinc, magnesium and fish oil, randomized controlled trials with sufficient power to detect clinically important differences in maternal and infant outcomes are needed.

Zinc status in pregnancy: the effect of zinc therapy on perinatal mortality, prematurity, and placental ablation

Zinc is present in and indispensable to all forms of life. Zinc is essential for the normal growth of human beings, and zinc proteins have been shown to be involved in the transcription and translation of the genetic material. Zinc deficiency has been incriminated in infertility, abortions, malformations, fetal intrauterine growth retardation, premature and postmature births, perinatal death, and abnormal deliveries with dystocia and placental ablation. Risk groups for developing zinc deficiency, which in turn might modify the expression of the underlying disease, are found among those with insufficient food intake, especially in protein malnutrition; abnormal mucosal uptake, as in celiac disease; abnormal intestinal losses, as in steatorrhea and inflammatory bowel disease; abnormal renal excretion, as in diabetes with insufficient metabolic control; alcoholism; and treatment with diuretic drugs. Zinc deficiency could be identified by means of fasting serum or plasma samples or the more laborious estimation of zinc in leucocytes or monocytes if sampling and handling is carefully performed and if stressful situations and acute-phase reactions as fever, delivery, or abortion are avoided. Zinc therapy in identified low-zinc groups has given favorable results and has reduced the frequencies of premature birth, placental ablation, perinatal death, and postmaturity. It is suggested, as we did in 1980, that these data are compatible with the presence of a zinc-deficiency syndrome in pregnancy, which includes increased maternal morbidity, abnormal taste sensations, abnormally short or prolonged gestations, inefficient labor, atonic bleeding, and increased risks to the fetus such as malformations, growth retardation, prematurity, postmaturity, and perinatal death.

Midpregnancy plasma zinc in normal and growth retarded fetuses--a preliminary study

OBJECTIVE

To determine plasma zinc concentrations in normally and abnormally growing fetuses.

DESIGN

Prospective observational study.

SETTING

Fetal Medicine Unit, Queen Charlotte's Maternity Hospital.

SUBJECTS

53 pregnant women attending for fetal blood sampling at between 18 and 40 weeks gestation. 27 fetuses were normal (central group), 11 fetuses were growth retarded and 15 were malformed.

MAIN OUTCOME MEASURES

Plasma zinc concentrations in maternal and fetal blood at time of fetal blood sampling.

RESULTS

In normally growing fetuses, between 18 and 40 weeks gestation, there was no fall in maternal plasma zinc concentration; the fetal level fell by 36%. In 10 fetuses with symmetrical growth retardation, plasma zinc concentration tended to be low, but was not significantly different from that in the normal control fetuses.

CONCLUSION

The results suggest that (i) placental transfer of zinc is an uphill secretory process and that it is a rate-limiting step in the accumulation of zinc by the fetus and (ii) in fetuses with symmetrical intrauterine growth retardation, a low plasma zinc is probably a parallel phenomenon and not necessarily an aetiological factor.

The role of zinc in reproduction. Hormonal mechanisms

Zinc is a very important element in the reproductive cycle of species. In humans, it is necessary for the formation and maturation of spermatozoa, for ovulation, and for fertilization. During pregnancy, zinc deficiency causes a number of anomalies: spontaneous abortion, pregnancy-related toxemia, extended pregnancy or prematurity, malformations, and retarded growth. Delivery is adversely affected by deficiency. These different effects of zinc can be explained by its multiple action on the metabolism of androgen hormones, estrogen and progesterone, together with the prostaglandins. Nuclear receptors for steroids are all zinc finger proteins. Zinc supplementation has already proven beneficial in male sterility and in reducing complications during pregnancy. However, it would be worth conducting larger-scale trials to confirm these beneficial effects.

Hormonal effects of zinc on growth in children

Zinc deficiency impairs the metabolism of thyroid hormones, androgens, and above all growth hormones. In view of their important role in growth, it is not surprising to find growth disorders associated with zinc deficiency. Stunted growth linked to zinc deficiency is found during gestation, and also in the newborn and children up to adolescence. Depending on the country, 5-30% of children suffer from moderate zinc deficiency, responsible for small-for-age height. Zinc supplementation has proven effective in many studies, mainly in children where zinc deficiency has first been found. Finally, zinc supplementation makes it possible in certain cases to overcome resistance to growth hormone treatment.

The relationship between maternal serum zinc levels during pregnancy and birthweight

A retrospective follow-up study to ascertain the relationship between the level of serum zinc and its rate of change during gestation and birthweight was conducted in 476 women of lower socioeconomic status. Serum zinc concentrations measured at approximately 16 (early) and 32 weeks (later) in gestation were both found to be significant predictors of birthweight. Even after controlling for gestational age at birth and other determinants of birthweight, for each microgram/dl increase in serum zinc early and later in pregnancy, birthweight increased by 5.8 and 8.6 g, respectively. Furthermore, after adjustment for initial zinc levels both the total change (beta = -7.0, P = 0.0007) and the rate of change (beta = -60.8, P = 0.007) in serum zinc during pregnancy were inversely associated with birthweight, i.e., the larger the fall in serum zinc during pregnancy, the smaller the infant. Low serum zinc level (less than 60 micrograms/dl) late in pregnancy was associated with greater than a five-fold increase in the odds (OR = 5.8, 95% CI = 1.8, 16.4) of giving birth to a low birthweight infant. The results of this study suggest a threshold for maternal serum zinc below which the prevalence of low birthweight increases rapidly.

Plasma zinc and copper in pregnant Nigerian women at term and their newborn babies

The concentration of copper and zinc was determined by atomic absorption spectrophotometry in 26 normal Nigerian women at term and their newborn babies. Cord zinc was significantly greater than maternal zinc. In contrast, cord copper was lower than maternal copper. There was only a weak correlation between cord copper and maternal copper but none between cord zinc and maternal zinc. There was no correlation between maternal and cord zinc and neonatal birthweight. However, an inverse correlation was found between maternal and cord copper and neonatal birthweight. These results indicate that: (1) zinc has no effect on fetal growth in Nigerian women but (2) copper may have a negative effect on fetal growth.

Zinc supplementation during pregnancy: a double blind randomised controlled trial

OBJECTIVE

To see whether zinc supplementation during pregnancy improves maternal and fetal outcome.

DESIGN

Prospective study started at booking and continued till discharge of mother and baby from the maternity hospital. Mothers were randomly assigned to receive zinc supplementation or placebo in a double blind trial.

SETTING

Mothers booking at one hospital.

PATIENTS

Women booking before 20 weeks of gestation who agreed to take part in the study. 494 Mothers were followed up till the end of pregnancy. There was no difference between the groups given zinc and placebo in their social or medical backgrounds.

INTERVENTIONS

Mothers in the active treatment group received one capsule of 20 mg elemental zinc daily and those in the placebo treated group a capsule identical in appearance and taste with the active capsule but which contained inert substances.

MAIN OUTCOME MEASURE

Various adverse outcomes were tested, including maternal bleeding, hypertension, complications of labour and delivery, gestational age, Apgar scores, and neonatal abnormalities. The main outcome measure was birth weight.

RESULTS

There were no differences whatsoever between mothers given a zinc supplement and those given a placebo.

CONCLUSION

Zinc supplementation in pregnancy in the United Kingdom does not seem to offer any benefits to the mother or her fetus.

Zinc and copper concentration in plasma of pregnant women in Nigeria

The concentration of plasma zinc and copper were determined by atomic absorption spectrophotometry in 58 Nigerian women at various times in pregnancy and compared with those of 11 non-pregnant controls. The results showed 67.5% decrease in zinc and 100% increase in copper over non-pregnant levels at the end of pregnancy. The mean plasma zinc levels were appreciably lower and copper the same as published values for Caucasian women at similar periods in pregnancy. Furthermore, there was no correlation between plasma zinc and copper and neonatal birthweight. We conclude that (1) a significant proportion of pregnant women in Nigeria have biochemical hypozincemia; (2) this hypozincemia is not responsible for fetal growth retardation in this population and (3) there is at present no justification for giving routine zinc supplementation to pregnant women in Nigeria.

Plasma and erythrocyte zinc concentrations in pre-eclampsia

Plasma and erythrocyte zinc concentrations were measured in 28 Chinese pre-eclamptic women and 28 controls matched for parity, race and gestation. There were no differences in either the plasma or erythrocyte zinc concentrations between pre-eclamptic and control groups, although the mean birth weight (p less than 0.001) and period of gestation (p less than 0.001) at delivery in the control group were significantly higher. In the pre-eclamptic patients, those delivering before 37 weeks or those who gave birth to low birth weight (less than 2500 g), babies had a significantly higher plasma urate concentration (p less than 0.02) compared to the pre-eclamptic patients with better fetal outcome. However, the plasma and erythrocyte zinc concentrations between these subgroups were not significantly different. Our results suggest that zinc deficiency is unlikely to play a significant role in pre-eclampsia in our patients, and that measurement of plasma and erythrocyte zinc concentrations is of doubtful clinical value in the management of pre-eclampsia.

The effect of maternal smoking on the relationship between maternal and fetal zinc status and infant birth weight

We have previously reported a trapping of zinc in the placenta directly related to circulating cadmium that comes from cigarette smoke. The purpose of this study was to examine in detail the effect of smoking on (a) the relationship between maternal and fetal zinc status and (b) the relationship between zinc status and birth weight. One hundred and eighteen smokers and 172 nonsmokers without any medical complications during pregnancy were studied. Atomic absorption spectroscopy was used to assess zinc status in maternal and cord vein plasma and red blood cells. Plasma alkaline phosphatase was also determined as an index of zinc status. Thiocyanate was used as an index of smoking status. The data were analyzed using univariate correlations and repeated measures analysis of variance. Infants of smokers had a statistically significant decrease in plasma zinc (5%), alkaline phosphatase (13%), and in cord vein RBC zinc (12%). Furthermore, the results showed an altered relationship between maternal and fetal indices of zinc status and zinc status and birth weight due to maternal smoking. The infant of the nonsmoking mother appears to be able to maintain adequate zinc status due to depletion of maternal zinc. However, it appears that the infant of the smoking mother may be marginally zinc deficient. These findings support studies of zinc supplementation in the pregnancy complicated by smoking.

Zinc concentration in umbilical cord tissue and cord plasma in appropriate-for-gestational-age babies

Zinc concentration in cord plasma was determined in 148 healthy appropriate-for-gestational-age babies delivered at various gestational ages. Zinc concentration in cord tissue was also determined in 62 of these babies. There was a significant rise in the cord tissue zinc concentration just after the 35th week of gestational age; thereafter the levels remained relatively unchanged. The cord plasma zinc concentration decreased slightly with increasing gestational age, but these changes were not significant. There was a statistically significant positive correlation between cord tissue zinc concentration and birth weight. No correlation was found between cord plasma zinc concentration and birth weight or cord tissue zinc concentration.