Archives of

 
 
 

Results

Evaluation of Maternal hematocrit levels:
One of the major causes of low birth weight is maternal anemia during pregnancy. Moreover, in the case of high concentration of hemoglobin, the risk of adverse pregnancy outcome will be high (9). In a study conducted by Ramezanali (1986), it was found that there are relationships between risk of low weight (lower than 2500 grams) and maternal hematocrit levels in first and third trimesters, mother's height, age, nationality, gestational age during pregnancy. No significant relationship was reported between maternal anemia and low birth weight and this is mostly emphasized in literature (9-13). In Ramezanali (1986), the average weight of babies whose mothers had normal hematocrit (between 36 and 39) was significantly more than those of whose mothers had over normal hematocrit. In addition, the average weight of babies whose mothers have naturally high hematocrit (between 39 and 42) were also significantly more than the average weight of babies whose mothers congested, hematocrit higher than 42 (9). Bondevik et al study aimed at investigation of the relationship between maternal hematocrit and risk of low birth weight and preterm delivery. It was found that maternal hematocrit item is clearly associated with higher birth weight in the first trimester (14). In the studies conducted by Ramezanali and Stevenson et al., it was concluded that high hemoglobin was related to the risk of low birth weight (9,15). In addition, in a study by Bondevik et al it was reported that high maternal hematocrit (over 40) has no relationship with increased risk of low birth weight (14). The reasons for the differences in results can be due to low birth weight of samples with high hematocrit, non-definition of high hematocrit in different studies, as well as biological and racial differences between observed populations.
 
Evaluation of relationship between hemoglobin concentration and body mass index and birth weight:
 The rate of low birth weight as one of the most common problems in neonatology was reported 7.7% in all races. Anemia in pregnant women are approximately 56%, 18% and 80% in developing countries, developed countries, and South Asia, respectively (9,16).
 
 Relationship between hemoglobin and birth weight:
Anemia is the most common nutritional deficiency in the world, especially in the developing countries (17-18), such that 25 to 50 percent of the world's population and almost 50 percent of pregnant women suffer from anemia (19).
In studies conducted by Salimi S, Faraji) et al (2010) and Laflam (2006) it was found that there is no relationship between low maternal hematocrit values ​​(less than 37) and preterm delivery as well as intrauterine growth retardation and low birth weight. Moreover, Bondevik et al (2001)) showed no meaningful relationship between the hemoglobin concentration in the first and third trimesters of pregnancy and birth weight (11,14, 20-22). Contrary, several studies revealed other results. In a study by Steer et al, Akanln et al (2000), and Ramezanali (9) (2006), it was shown that the increased risk of low birth weight in anemic women has a relationship with early pregnancy. In addition, Deshmukh et al (1998) indicated that maternal anemia was a major risk factor for low birth weight (23-25). While, Stevenson et al manifested that there was relationships between hemoglobin concentrations at first measurement during pregnancy care and an increased risk of stillbirth, preterm birth and small gestational age (SGA) (26).
 
The relationship between maternal BMI and birth weight:
In a study by Salimi et al and Kari (2008) a direct relationship was observed between maternal BMI and birth weight (20,27). In research by Singh et al (2009), maternal BMI less than 20 during pregnancy was among maternal factors mostly leads to low birth weight infants (28). Studies conducted by Sharifzadeh (2008) and Wise et al (2010) showed that low maternal pre-pregnancy body mass index has relationship with preterm birth and intensive low birth weight; and high maternal body mass index were related to macrosomia and high birth weight (29-30). Research by Khashan et al (2009) (34) suggested that obese women have an increased risk of macrosomia and cesarean rate and a lower risk of preterm birth. Contrary to Sharifzadeh, Rosenberg et al (2003) (35) stated that the period of pregnancy and the risk of preterm birth were not correlated with BMI in Chinese mothers. The reason for these different outcomes can be attributed to racial differences. A common point which was common almost in all of the studies reviewed was a direct correlation between pregnancy weight gain and birth weight (31,32,33).
 
Evaluation of relationship between maternal blood lead level and low birth weight infants:
In Mansouri M. (2009) it was shown that maternal blood lead levels strongly correlated with lead levels in cord blood and breast milk. Moreover, lead is easily transmitted from mother to fetus so that the cord blood lead concentration is approximately 80-90% of maternal blood lead concentrations (36-37). Increased blood lead levels may be due to high amount of lead in air, water, dust and food (37). Based on the results of Mansouri M. et al and West et al, higher maternal blood did not lead to infant weight reduction (36,38). In Mc Michael et al, maternal blood lead levels had no relationship with miscarriage, low birth weight, intrauterine growth retardation and congenital anomalies (39). Several studies showed that there was no relationship between birth weight and maternal lead levels. Currently lead level relationship with low birth weight is unclear (40-42).
 
Iron status in pregnant women and its relationship with infants:
Iron deficiency anemia is the most common type of anemia in pregnant women in the world may result in premature birth, as well as increased maternal and child mortality. Iron deficiency anemia in mothers affects fetal hematopoietic potential and fetal development. Hemoglobin, ferritin, and reticulocyte levels of infants are significantly related to maternal iron level (43). In Todd D study, it was found that birth weight and maternal hemoglobin and ferritin levels are inversely related. Because the larger and more weight infants need more iron and this further increases the risk of iron deficiency in the mother (44). In a study conducted by Emam Qureyshi F., it was extracted that there was a significant and direct relationship between increased number of deliveries and iron deficiency anemia in mothers. Iron deficiency in mothers is due to frequent pregnancies (43).
 
Evaluation of effect of maternal serum zinc levels on weight infants:
Zinc reduction during pregnancy can be attributed to the disproportionate increase in plasma volume, or the embryos-maternal transfer, reduction in binding of zinc, or zinc reduction in the diet, or the high volume of copper or even iron competence with zinc during absorption in the diet (44-46). In Rahimi (2010) research conducted in Ardebil City it was manifested that maternal serum zinc levels in Ardebil city were lower than normal; and it was reduced with increasing gestational age, but its level was not significant correlated with birth weight (8). In addition, in another study conducted by Avsondrop et al and Tamura et al, it was concluded that the there was no significant difference among the groups receiving the zinc and placebo in terms of infants' birth weight, head circumference, arm circumference, and gestational age. These studies suggested that in patients with malnutrition the rate of zinc absorption is low, and its dose should be doubled for pregnant women (47-48). However, in a study carried out in 18 developing countries a positive relationship was observed between the level of maternal lead level and infant birth weight. This difference results in different studies may be as a result of differences in sampling, laboratory methods, and the quality as well as size of the sample (49).
 
 
 
 
 
 

Conclusion

 
 
Finally, it should be mentioned that maternal parameters have adverse effects on the fetus; however none of them have been definitively proven. Perhaps the reasons for this difference in results are due to differences in race, geography, lifestyle, laboratory practices and etc. For this reason, it is recommended to carry out larger studies in any region where the precise effect of these parameters can be determined.
 
 

Footnotes

Conflict of Interest:
The authors declared no conflict of interest.