Hameed E. R. A, Sherif L. S, Awad A. H, Ashry H. H. E, Ahmed H. H, Sallam M. M, Fahmy R. F, Kamhawy A. H. Arsenic and Cadmium Levels in Maternal and Umbilical Cord Blood and their Associations with Birth Outcomes. Biomed Pharmacol J 2020;13(1).

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Manuscript received on :26-08-2019
Manuscript accepted on :01-01-2020
Published online on: 23-01-2020

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Plagiarism Check: Yes
Reviewed by: Dr.Chaitany Patel
Second Review by: felor zargari
Final Approval by: Dr Ayush Dogra

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Enas R.Abdel Hameed¹, Lobna S. Sherif¹, Amina H.Awad¹, Hala H. El Ashry¹, Hanaa H. Ahmed², Mona M.Sallam¹, Reham F. Fahmy^1* and Alyaa H. Kamhawy¹

¹Child  Health Department, Medical  Research  Division, National  Research  Centre, Giza, Egypt

²Hormones Department, Medical Research Division, National Research Centre, Giza, Egypt

Corresponding Author E-mail : Reham_dodo2@yahoo.com

DOI : https://dx.doi.org/10.13005/bpj/1861

Abstract

Exposure to heavy metals as cadmium and arsenic during pregnancy may have unfavorable effects on pregnant women and their offsprings. The aim of the study is to characterize the concentrations of arsenic   and cadmium in umbilical cord blood and maternal blood and to clarify their associations with certain epidemiological maternal variables and birth outcomes. This cross- sectional study was conducted on randomly chosen 113 pregnant mothers and their newborns. Full history and sociodemographic data were recorded. Inductively Couples Plasma Mass Spectrometry was used to assess the   levels of arsenic and cadmium in maternal and cord blood serum samples. There was a significant negative association between gestational age and maternal serum level of arsenic (r=-0.368, P=0.04). There was a significant negative correlation  between   maternal serum levels of arsenic and cadmium with Apgar score at 1-minute (r=-0.352, -0.361, P= 0.04, 0.032 respectively). No significant correlation was found between maternal serum levels of arsenic and cadmium and neither maternal education nor maternal age. The current approach   states that maternal exposure to arsenic and cadmium during pregnancy has been found to be harmful to the developing fetus. The outcomes of the present work highlight the importance of avoiding prenatal exposure to heavy metals.

Keywords

Arsenic; Birth Outcomes; Cord Blood; Cadmium; Pregnant Women

Introduction

Exposure of mothers during pregnancy to various trace elements and heavy metals, which incorporate lead, cadmium, arsenic, mercury and aluminum could be of damaging impact to the developing fetus, ^{1, 2}, even at low levels of exposure.³ Also, exposure to environmental contaminants  during pregnancy may have an extended harmful effects in early childhood and  later in life.⁴ A significant positive correlation has been demonstrated between maternal serum levels of mercury and cord blood mercury concentration ⁵ which may induce a hazard to the fetus. Some investigators detected an inverse relationship between total mercury   concentration in cord blood and fetal growth.⁶ Cord blood lead concentration showed significant positive correlation with head circumference and birth weight.⁷

Cadmium pollution of the environment is omnipresent due to activities of the industries, usage of phosphate fertilizers, burning of motor fuels in means of transportations and particles released by tyre wear, all of which produce emissions to air, soil and water.^{8, 9} In non-smokers, diet is considered the main significant source of exposure to cadmium. In smokers, tobacco is the main significant source, as tobacco, like other plants, takes up cadmium, which is inhaled in the smoke.¹⁰ Also, cadmium can be present at increased levels in food for instance shellfish, organ meats, cereals, root vegetables, and green leafy vegetables.¹¹

Cadmium exposure is considered of great importance owing to its probable burden on fetal health in spite that the placenta acts as a barrier, which protect the fetus from exposure to cadmium by enhancing metallothionein expression.¹²  This metal has been shown to be correlated with reduced birth weight ^{1, 13}, premature delivery ¹⁴ and changed thyroid hormone condition of newborn.¹⁵

Exposure to arsenic (AS) is primarily oral, which results mostly from drinking water sources. In areas of the world in which water contains arsenic concentrations of more than 50µg/L, the small children can be at considerable risk for both cancer and neural deterioration.¹⁶ The   evidence of the contribution of arsenic in causing unfavorable human reproductive outcomes is increasing. It has been supposed that maternal exposure to arsenic early in pregnancy negatively influences newborn’s birth weight.¹⁷  Fish, shellfish, poultry, dairy products, meat and cereals are sources of arsenic in diet, though exposure from these foods is much lower in comparison to exposure through contaminated groundwater. Now, human bodies are continuously being tainted by dietary and commercial product ingredients and become simply over burdened by toxins. This could be elucidated by changes in modern life styles.¹⁸ Comparable data, solely for pregnant women, have been studied confirming that. Unfortunaly, there are no safe blood level values for any of the heavy metals that have any degree  of transfer through the placenta to the fetus during pregnancy. The only way of decreasing fetal exposure is to lessen maternal exposure.¹⁹

The goals of the present work were to characterize the concentrations of arsenic (As) and cadmium (Cd) in umbilical cord blood and maternal blood and to clarify their associations with certain epidemiological maternal variables and birth outcomes (gestational age, head circumference, and Apgar score at 1-5 minutes) .

Subject and methods

This cross- sectional study was conducted on 113 newborn -mother couples who were randomly chosen from those attending Al-Galaa Maternity Educational Hospital in the period between    September    2016 to  June 2017. The mothers’ ages ranged between 16 and 45 years. Pregnant mothers with history of chronic diseases or major illnesses during pregnancy were excluded. Elective caesarean sections were enrolled in the study. Neonates with any apparent congenital anomalies, metabolic, genetic or neurological problems were also excluded. This study was funded by the National Research Centre11^th research plan, entitled “Immunological profile in cord blood and growth assessment of the newborn in relation to maternal exposure to environmental contaminants”. The study protocol was approved by the Medical Ethical Committee of the National Research Centre (Approval code: 16/295). Written informed consent was provided by all mothers who participated in this study after explaining the background, objectives, and benefits of the study. The mothers also signed the informed consent on behalf of the neonates enrolled in the study. Verbal oral consent was   obtained from illiterate mothers.

All Mothers were subjected to the Followings

Full history taking laying stress on: mother’s age, education, occupation, residence, the order of child birth, water source availability, sanitary disposal, and smoking status during pregnancy. Exposure to environmental tobacco smoke (ETS) was defined as exposure to tobacco smoke from smoking by others in the household.²⁰

Perinatal  history : included gestational age (in weeks), type of labor, history of delivery problems.

Maternal anthropometric measures: The height and weight of mothers were recorded just before delivery according to a standard protocol suggested by the World Health Organization.²¹ Body weight was measured in lightweight clothing to the nearest 0.1 kg using a portable digital balance (Tanita scale). Height was measured to the nearest 0.1 cm without shoes, using a portable stadiometer (Harpenden stadiometer) .

All the included neonates were subjected to the following

Physical examination: Neonates were subjected to thorough clinical examination by the pediatrician that included chest, heart, abdomen, and central nervous system examination. The Apgar score was also measured to assess neonatal   condition at birth on a scale from 1 to 10, at 1 and 5 minutes after delivery. Infants were evaluated on a scale of 0 to 2 according to five categories (skin color, muscle tone, reflexes, respiratory effort, and heart rate), and the points from each category added together to determine the total score ²².

Anthropometric data were measured, before breast feeding started. Newborns were weighed (in kilograms) without diapers and using an electronic digital infant scale (Laka). Length (in centimeters) was measured in the supine position, using a stadiometer (Seca 416) composed of a stationary head-board and a movable foot board. Head and mid upper arm circumferences (cm) were also measured.²³

Sample collection

Ten ml of venous blood was collected from the mothers at the time of labor either in normal or section delivery, and then centrifuged under cooling (4^oC) at 1800 xg  to separate serum samples which were stored at -70^oC pending laboratory analysis.

10 ml of cord blood was collected from an immediate clamped ,isolated piece of the umbilical cord of the newborn during delivery before placental separation and put on EDTA free tubes, then centrifuged under cooling (4^oC) at 1800 x g to separate serum samples which were preserved at – 70^oC until laboratory investigation.

Determination of heavy metals (arsenic and cadmium) in serum samples

Principle Determination of toxic elements in traditional medicine was done using Inductively Couples Plasma Mass Spectrometry (PerkinElmer

ELAN ICP-MS DRC II), PIN 5989-559 IEN. This method is provided to determine

As, Cd, and  other metals in biological   samples.

Method

Sample Preparation

For   the   determination  of  serum  heavy metals, the serum samples were diluted with an equal volume of deionized water (1:5). The dilution ratio was adjusted to insure that concentration fall within a suitable absorbance range.

Estimation of As, and Cd, in serum samples

The diluted samples   were   injected   into  Inductively  Couples  Plasma  Mass Spectrometry (ICP mass) and the calibration curve for each metal was plotted. Then the concentration of each metal in each sample was estimated from the corresponding curve of each metal. Good precision and accuracy 1_3% for solution mode.

Accuracies and precisions for most elements are typically on the order of 1_3% for solution mode.

Statistical analysis

Analysis was performed using SPSS 21 (SPSSINC, Pennsylvania,  USA). Mean + SD and percent were used for parameters’ distribution calculations. Correlation was done using pearson’s correlation. P<0.05 value   was considered as significant and P<0.005 value  as highly significant.

Results

A total of 113 mother-newborn pairs were enrolled in this study. The mean of maternal age was 26.7 + 5.6 years. The mean of gestational age was 36.9 + 2.1 weeks. 45.1% of the newborns were males and 54.9% were females. 55.8% of the newborns were delivered vaginally and 44.2% had caesarean section delivery. About 93% of mothers had history of passive smoking exposure. The source of drinking water in 99% of the study population was tap water which is a safe source of water compared to those depending on other sources such as the shallow wells. The maternal and neonatal sociodemographic characteristics are shown in Table (1).

Table 1: The maternal and neonatal sociodemographic characteristics

The anthropometric measurements of mothers and neonates are shown in Table (2)

Table 2: The anthropometric measurements of mothers and neonates

The mean concentrations of maternal serum arsenic and cadmium levels were 59.7+9.2 and 0.7+0.4 respectively. The mean concentrations of cord blood levels of arsenic and cadmium were 3.5+7.6 and0.7+0.3 respectively as shown in Table (3).

Table 3: The mean of concentrations of arsenic and cadmium in maternal and cord blood:

There was a significant   negative correlation between maternal serum level of arsenic and gestational age (P<0.05). On the other hand, no significant correlation could be detected between   maternal   serum level of cadmium and cord blood concentrations of arsenic and cadmium and gestational age (P>0.05). There was no significant correlation between serum levels of arsenic and cadmium in maternal and cord blood with the head circumference of the newborns (P>0.05). There was a significant negative correlation between serum level of arsenic in maternal blood and the Apgar score at 1- minute and 5- minutes (P<0.05). In addition, there was a significant negative   correlation between maternal serum level of cadmium and the Apgar score at 1-minute (P<0.05).  No significant correlation between serum levels of arsenic and cadmium in maternal and cord blood and maternal education could be detected. The correlations of the study were shown in Table (4).

Table 4: Correlations between maternal and cord blood levels of arsenic and cadmium   and gestational age, head circumference, Apgar score of the newborns, and maternal education

*Significant test  :P<0.05.

The serum levels of cadmium and arsenic in maternal blood and cord blood cadmium concentration were significantly higher in mothers who were passively exposed to environmental tobacco smoke compared to the non- exposed mothers (P<0.05) as shown in Table (5).

Table 5: Comparison between mothers who were passively exposed to tobacco smoke and the non-exposed mothers as regards the maternal and cord blood levels of arsenic and cadmium

* P<0.05 :   significant.

Discussion

The intrauterine environment doesn’t constantly protect the fetus from environmental factors as shown by different epidemiological studies. Exposure of mothers to stress, dietary factors, and environmental chemicals have a considerable impact on fetal growth and fetal development ²⁴. Consequently, deficiency or over exposure of certain trace elements might be harmful to the health of both pregnant women and their fetuses ^25.

The present study showed a significant negative correlation between serum level of arsenic in maternal blood and gestational age (P< 0.05).This comes in line with Xu et al ²⁶ and Enas et al ¹³ who reported that gestational age was inversely related to arsenic concentration in mothers’ whole blood. Also, Shi et al ²⁷ found that preterm birth has a stronger spatial relationship with ground water arsenic than term low birth weight implying an inconsistency in the effect of arsenic on the two reproductive outcomes. A study done in India found that exposure to high concentrations of arsenic (200 µg/L) during pregnancy was correlated with a six- fold raised   risk of stillbirth ²⁸. The probable explanation could be   that inorganic arsenic (iAs) traverses the human placenta, and accumulates in the developing organs and systems of the fetus, promoting  an increased risk potential.²⁹ Observational evidence proposes that iAs accumulates in and disrupts placental function ³⁰ and changes DNA methylation in cord blood ³¹.It has been reported that abnormal placentation is a powerful risk factor for preterm delivery and restricted fetal growth.³²

There was non -significant correlation between serum level of cadmium in maternal blood and gestational age (P >0.05).

Similarly, Johnston et al, ¹ reported that gestational age at delivery did not differ by blood cadmium levels. On the other hand, Röllin et al, ²⁰ stated that mothers of infants who were born preterm had a higher geometric mean for cadmium level in blood in comparison to the mothers of infants born at term but this finding was not significant. The findings of Amayaet al,  ³³  indicated that gestational age was associated with placental cadmium concentration. Here in, we did not detect a significant correlation between cord blood arsenic and cadmium concentrations and gestational age (P>0.05). However, the existence of cadmium in cord blood has been related with increased incidence of preterm   delivery.¹⁴

Our study demonstrated   no significant correlation between serum levels of arsenic and cadmium in maternal blood and cord blood with head circumference of the newborn (P>0.05). This result agrees with is in accordance with Johnston et al, ¹ and Röllin et al, ²⁰ who also found that cadmium levels were not associated with head circumference. This could be attributed to the function of   the placenta as being an efficient barrier against cadmium passage ³⁴. On the other hand,  Rahman et al, ³⁵demonstrated that a one µg g/L increase in averaged urine inorganic arsenic values was associated with a0.05 mm head circumference reduction (P=0.04).

The present study revealed a significant negative correlation between serum level of arsenic in maternal blood and the Apgar 1-minute and Apgar 5-minute score (P<0.05).In addition, there’s a significant negative correlation between serum level of cadmium in maternal blood  and the Apgar 1-mimute score (P<0.05) but not with Apgar 5-minute score (P>0.05). No significant correlations could be detected between cord blood cadmium and arsenic concentrations and the Apgar 1-minute and 5-minute scores (P>0.05).These results were in contrast with the findings of other studies. Mokhtar et al, ³⁶ registered a negative association between cord blood  cadmium and the 5-miunte Apgar score, in 100 Egyptian newborns who had a mean cord blood cadmium level of 0.66 µg/L. Garcia- Esquinaset al, ³⁷stated that newborns with cord blood cadmium concentrations over 0.29µg/L had less 1-minute and 5-minute Apgar scores than those with lesser concentrations. The study carried out in Saudi Arabian population, ³⁸,  found   that newborns who had Apgar 5-minutes scores less than the 10^th percentile (0-8) had high levels of umbilical cord blood cadmium. Apgar scoring permits the evaluation of the state of infants directly after birth.³⁹ In addition,  there is a proof   that lower 5-minute Apgar scores at birth may be linked with lower survival and neurological outcomes at the age of one year ⁴⁰ and during early adulthood.⁴¹ The causal biological mechanisms that explain   this association stays unclear.

The serum levels of arsenic and cadmium in maternal blood and cord blood cadmium concentration were significantly higher in mothers who were passively exposed to environmental tobacco smoke compared to the non- exposed mothers (P<0.05). Our findings are consistent with other studies .Butler Walker et al, ⁴²found that geometric mean blood cadmium in moderate smokers (1-8 cigarettes/day) and in heavy smokers (>8 cigarettes /day) was 7.4 fold higher and 12.5 fold higher, respectively, comparative to non- smokers. Guan et al, ⁴³, and Röllin et al, ²⁰also stated that maternal blood levels of cadmium were significantly elevated among mothers who exposed to second-hand smoke during pregnancy. In addition, Garcia- Esquinas et al, ³⁷ found that cadmium concentration was 22% higher in newborns from mothers who smoked during   pregnancy than those who non-smoked ones. The smoke of cigarette is a well recognized source of human exposure to cadmium. An average cigarette has 1-2 µg of cadmium, of which smokers take up a part via inhalation.⁴⁴ One cigarette has been found to raise the blood cadmium level by 0.1-0.2 µg/L.⁴⁵

Our study revealed that there was no significant correlation between maternal blood arsenic and cadmium concentrations   and cord blood concentrations of arsenic and cadmium (P>0.05) (results not shown). Similarly, Rudge et al, ⁴⁶, and Röllin et al ²⁰ stated that there was no significant correlation between maternal and cord blood as regards cadmium concentration. However, other studies demonstrated a significant positive correlation between maternal and cord blood concentration of  arsenic and cadmium.^{47, 43 ,37} The contradictory results between studies could be attributed to the dose, timing of exposure, and the dynamic physiological changes that occur in pregnant women.⁴⁸  The current study did not find significant correlations between maternal and cord blood concentrations of arsenic and cadmium and either maternal age or education (P>0.05). Similarly, Röllin et al ²⁰ found that maternal age and education had no effect on cadmium levels. In contrast, Liu et al, ⁴⁸ demonstrated that among different age intervals, the concentration of maternal serum arsenic and cadmium significantly increased with increasing age. Age is the one of the first parameters that has an effect on the body burden of trace elements.⁴⁹  Parajuli et al, ⁵⁰ reported that the maternal age was negatively associated with the cord blood arsenic level and the cord blood arsenic level from less educated mothers was higher than those from educated mothers. Less educated mothers mostly come from families with lower socioeconomic status. Some studies stated that children with lower socioeconomic status have higher exposure to several chemical pollutants than those with higher socioeconomic status ⁵¹.Shi et al, ²⁷ showed that younger maternal age has stronger spatial correlations with ground water arsenic. The positive spatial relationship between low birth weight and arsenic level is observed for maternal age <25 years.²⁷

We have some limitations in this study. The small sample size which could not  help to identify significant relation between variables. Therefore,  carefulness  is required during analysis of the results. In addition, concern should be taken as regards the design   that choose productive couples during the third trimester of pregnancy, which means that if metals influence fertility or lessen pregnancy length, the concentration in our adult sample could be undervalued the levels in the general population. Also, we did the anthropometric measurements one time on infants, leading to a possible resource of measurement error.

Conclusion

It becomes clear that prenatal exposure to heavy metals such as arsenic and cadmium may have a direct influence on birth outcomes. For that reason, improving socioeconomic status and educating mothers as regards the sources of exposure to these heavy metals could potentially decrease the hazards on their newborns.

Recommendations

The study highlights the possible hazardous effect of prenatal exposure to arsenic and cadmium on newborns and emphasizes the require for better understanding the role of dietary, occupational, environmental, and life style which affect their exposure levels. Mothers should be advised to avoid tobacco smoke exposure as it’s a significant avoidable source of heavy metal exposure in newborns.

Acknowledgment

The authors would like to thank the National Research Center for funding this research work, (Grant number: 16/295).

Conflicts of interest

The authors declare no conflict of interest.

References

1. Johnston J.E, Valentiner E, Maxson P, Miranda M.L, and Fry R.C: Maternal cadmium levels during pregnancy associated with lower birth weight in infants in a North Carolina Cohort. P 2014;9(10): e109661.
   CrossRef
2. Nadeau K.C, Li Z, Farzan S, Koestler D, Robbins ,D,Fei D.L, Malipatolla M, et al: In utero arsenic exposure and fetal immune repertoire in a US pregnancy cohort. Clin .Immunol. 2014 ; 155:188- 197.
   CrossRef
3. Ha M, Kwon H.J, Lim M.H, Jee Y.K, Hong Y.C, Leem J.H, Sakong J et al: Low blood levels of lead and mercury and symptoms of attention deficit hyperactivity in children: A report of the children’s health and environment research (CHEER). Neurotoxicology.2009; 30:31-36.
   CrossRef
4. Gluckman P.D, Hanson M.A, Cooper C, et al: Effect of in utero and early- life conditions on adult health and disease. N. Engl.J.M.2008; 359:61-73.
   CrossRef
5. Enas R. Abdel Hameed, Lobna S. Sherif, Ola M. Abdel Samie, Hanaa H.  Ahmed, Amira Ahmed, Hala Atta ,et al: Mercury materno-fetal burden and its nutritional impact. Open Access Macedonian Journal of Medical Sciences.2018; 6(9): 1652-1658.
   CrossRef
6. Ramon R, Ballester F, Aguinagalde X, Amurrio A, Vioque J, Lacasana M, et al: Fish consumption during pregnancy, prenatal mercury exposure, and anthropometric measures at birth in a prospective mother-infant cohort study in Spain. Am J Clin Nutr.2009; .90: 1047-1055.
   CrossRef
7. Zych B, Sztanke M, Kulesza- Bronczyk B, Lewandowski B, Sztanke K, and Pasternak K: The analysis of selected microelements in neonatal umbilical cord blood. J. Elementol.2013; 18: 495-506.
8. ATSDR (Agency for toxic Substances and Disease Registry): Toxicological profile for Cadmium. Agency for Toxic Substances and Disease Registry: Atlanta, GA, USA, 2012. Available at: http://www.atsdr.cdc.gov/ toxprofiles /tp5-c6.pdf.
9. Pan J, Plant J.A, Voulvoulis N, Oates C.J and Ihlenfeld C: Cadmium levels in Europe: implications for human health. Environ Geochem Health.2010; 32:1-12.
   CrossRef
10. SatarugS, Garrett SH, Sens MA, and Sens D.A: Cadmium, environmental exposure, and health outcomes. Environ Health Perspect. 2010; 118:182-190.
    CrossRef
11. Egan SK, Bolger PM, Carrington CD: Update of US FDA’s Total Diet Study food list and diets. J Expo Sci Environ Epidemiol.2007; 17: 573-582.
    CrossRef
12. McAleer MF , Tuan RS (2001):Metallothionein overexpression in human trophoblastic cells protect against cadmium-induced apoptosis. In Vitr Mol Toxicol.2001; 14:25-42.
    CrossRef
13. Enas R Abdel Hameed, Manal A Shehata, Hanaa H Ahmed, Lobna S Sherif, Hala G Elnady, and Hisham Waheed: Relation of heavy metals in cord and maternal blood to neonatal anthropometric indices. Journal of Clinical and Diagnostic Research.2019; 13(3): SC01-SC05.
    CrossRef
14. Nishijo M, Nakagawa H, Honda R, Tanebe K, Saito S, Teranishi H, et al: Effects of maternal exposure to cadmium on pregnancy outcome and breast milk. Occup. Environ. Med.2002; 59: 394-396.
    CrossRef
15. Iijima K, Otake T, YoshinagaJ, Ikegami M, Suzuki E, Naruse H, et al: Cadmium, lead, and selenium in cord blood and thyroid hormone status of newborns. Biol Trace Elem Res.2007; 119: 10-18.
    CrossRef
16. Dopp E.K, Ligerman A.D, Diz – Bone R.A.: Organoarsenicals: Uptake, metabolism and toxicity. In: Sigel A, Sigel H, Sigel R.K.O, editors. Metal Ions in Life Sciences: Volume 7. Organometallics in Environment and Toxicology. Royal Society of Chemistry; London, UK.2010: pp. 231-265. Chapter 7.
17. Huyck KL, Kile ML, Mahiuddin G, Quamruzzaman Q, Rahman M, Breton CV, et al et al,: Maternal arsenic exposure associated with low birth weight in Bangladesh. J.Occup. Environ. Med.2007; 49:1097-1104.
    CrossRef
18. Schofield K: The Metal Neurotoxins: An important Role in Current Human Neural Epidemics?. Int J Environ Res Public Health.2017; 14 (12). Pii: E1511.
    CrossRef
19. Taylor CM, Golding J , Emond AM: Lead, cadmium and mercury levels in pregnancy: The need for international consensus on levels of concern. J Dev Orig Health Dis.2014; 5 (1): 16-30.
    CrossRef
20. Röllin HB, Kootbodien T, Channa K, and Odiand JO: Prenatal exposure to cadmium, placental permeability and birth outcomes in Coastal populations of South Africa. PLoS One.2015; 10(11):
    CrossRef
21. World Health Organization Obesity: Preventing and managing the global epidemic. WHO.2000; 894: 1-253.
22. Apgar V, Holaday DA, James LS, Weisbrot IM, and Berrien C: Evaluation of the newborn infant; second report. J Am Med Assoc.1958; 168: 1985-1988.
    CrossRef
23. World Health Organization. WHO child growth standards: length/height-for-age, weight-    for-age, weight-for-height and body mass index-for-age: Methods and development. Geneva,  Switzerland: World Health Organization; 2006. Available at http://www.who.int/ childgrowth/ publications/ technical_report_pub/ en/ index.html.
24. Balbus J.M, Barouki R, Birnbaum L.S, Etzel R.A, Gluckman P.D, Grandjean P, et al: Early- life prevention of non-communicable diseases. Lancet.2013; 381: 3-4.
    CrossRef
25. Strachan S: Trace elements. Curr .Anaesth. Crit. Care.2010; 21: 44-48.
    CrossRef
26. Xu L, Yokoyama K, Tian Y, Piao Fy, Kitamura F, Kida H, et al :  Decrease in birth weight and gestational age by arsenic among the newborn in Shanghai, China. Nihon Koshu Eisei Zasshi.2011; 58 (2): 89-95.
27. Shi X, Ayotte J.D, Onda A, Miller S, Rees J, Gilbert- Diamond D, Onega T ,et al: Geospatial association between adverse birth outcomes and arsenic in ground water in New Hampshire, USA. Environ. Geochem. Health.2015; 37: 331-351.
    CrossRef
28. Von Ehrenstein OS, Mazumder DNG, Hira- Smith M, Ghosh N, Ghosh N, Yuan Y et al: Pregnancy Outcomes, Infant Mortality, and Arsenic in Drinking Water in West Bengal, India. American Journal of Epidemiology.2006; 163: 662-669.
    CrossRef
29. Concha G, Vogler G, Lezcano D, Nermell B, and Vahter M: Exposure to inorganic arsenic metabolites during early human development. Toxicol.Sci.1998; 44: 185-190.
    CrossRef
30. Ahmed S, Mahabbat -e Khoda S, Rekha RS, Gardner RM, Ameer SS, Moore S, et al: Arsenic- associated oxidative stress, inflammation, and immune disruption in human placenta and cord blood. Environ. Health Perspect.2011; 119: 258-264.
    CrossRef
31. Pilsner JR, Hall MN, Liu X, Ilievski V, Slavkovich V, Levy D, et al : Influence of prenatal arsenic exposure and new born sex on global methylation of cord blood DNA. PLoS One.2012; 7.
    CrossRef
32. Murphy VE, Smith R, Giles WB, and Clifton VL: Endocrine regulation of human fetal growth : The role of the mother, placenta, and fetus. Endocr. Rev.2006; 27: 141-169.
    CrossRef
33. Amaya E, Gil F, Freire C, Olmedo P, Fernandez- Rodriguez M, Fernandez M.F et al: Placental concentrations of heavy metals in a mother- child cohort. Environ. Res. 2013; 120: 63- 70.
    CrossRef
34. Sakamoto M, Yasutake A, Domingo JL, Chan HM, Kubota M, and Murata K: Relationships between trace element concentrations in chorionic tissue of placenta and umbilical cord tissue: potential use as indicators for prenatal exposure. Environ Int.2013; 60: 106-11.
    CrossRef
35. Rahman A, Vahter M, Smith AH, Nermell B, Yunus M, El Arifeen S ,et al :Arsenic exposure during pregnancy and size at birth: Aprospective cohort study in Bangladesh. Am. J. Epidemiol.2009; 169: 304-312.
    CrossRef
36. Mokhtar G, Hossny E, el – Awady M, and Zekry M: In utero exposure to cadmium pollution in Cairo and Giza governorates of Egypt. East Mediaterr Health J.2002; 8: 254-260.
37. Garcia- Esquinas E, Perez- Gomez B, Ferndndez- Navarro P, Fernandez MA, de Paz C, Perez- Meixeira AM et al: Lead, mercury and cadmium in umbilical cord blood and its association with parental epidemiological variables and birth factors. BMC Public Health.2013; 13: 841.
    CrossRef
38. Al-Saleh I, Shinwari N, Mashhour A, and Rabah A: Birth outcome measures and maternal exposure to heavy metals (lead, cadmium and mercury) in Saudi Arabian population. Int J Hyg Environ Health.2014; 217 (2-3): 205-18.
    CrossRef
39. Rubarth L: The Apgar score: Simple yet complex. Neonatal Netw.2012; 31: 169-177.
    CrossRef
40. Juretschke LJ: Apgar scoring : its use and meaning for today’s newborn. Neonatal Netw. 2000 ; 19: 17 -19.
    CrossRef
41. Stuart A, Otterblad OP, Kallen K: Apgar scores at 5 minutes after birth in relation to school performance at 16 years of age. Obstet Gynecol.2011; 118: 201-208.
    CrossRef
42. Butler Walker J, Houseman J, Seddon L, Mc Mullen E, Tofflemire K, Mills C et al: Maternal and umbilical cord blood levels of mercury, lead, cadmium, and essential trace elementsin Arctic Canada. Environ Res.2006; 100 (3): 295-318.
    CrossRef
43. Guan H, Piao FY, Li XW, Li QJ, Xu L, and Yokoyama K: Maternal and fetal exposure to four carcinogenic environmental metals. Biomed Environ Sci.2010; 23(6): 458-65.
    CrossRef
44. Menai M, Heude B, Slama R, Forhan A, Sahuquillo J et al : Association between maternal blood cadmium during pregnancy and birth weight and the risk of fetal growth restriction: The EDEN mother- child cohort study. Reported Toxicol.2012; 34: 622-627.
    CrossRef
45. Jarup L, Berglund M, Elinder CG, Nordberg G, and Vanter M: Health effects of cadmium exposure: a review of the literature and a risk estimate. Scand J Work Environ Health .1998: 1-51.
46. Rudge CV, Röllin HB, Nogueira CM, Thomassen Y, Rudge MC, and Odland JǾ: The placenta as a barrier for toxic and essential elements in paired maternal and cord blood samples of South African delivering women. J.Environ Monit.2009; 11(7):1322-30.
    CrossRef
47. Wang P, Tian Y, Shi R, Zou XY, Gao Y, Wang MM, et al: Study on maternal- fetal status of Pb, As, Cd, Mn and Zn elements and the influence factors. Zhonghua Yu Fang Yi Xue ZaZhi.2008; 42(10): 722-6.
    CrossRef
48. Liu X, Zhang Y, Piao J, Mao D, Li Y, Li W, et al: Reference values of 14 serum trace elements for pregnant Chinese women : A cross-sectional study in the China nutrition and health survey 2010-2012. Nutrients.2017; 9 (3):Pii: E309.
    CrossRef
49. Jain R.B , Choi Y.C: Normal reference range for and variability in the levels of blood manganese and selenium by gender, age, and race/ethnicity for general US population. J. Trace Elem. Med. Biol.2015; 30:142-152.
    CrossRef
50. Parajuli RP, Fujiwara T, Umezaki M, Furusawa H, Ser PH, and Watanabe C:Cord blood levels of  toxic and essential trace elements and their determinants in the  Terai region of Nepal: a birth cohort study. Biol Trace Elem Res.2012; 147(1-3): 75-83.
    CrossRef
51. Naess O, Piro F.N, Nafstad P, Smith G.D, and Leyland A.H: Air pollution, social deprivation, and mortality : A multilevel cohort study. Epidemiology.2007; 18: 686-694.
    CrossRef