Total serum vitamin C concentration in pregnant women : implications for a healthy pregnancy

Objectives: total serum vitamin C (L-ascorbic acid) concentration was measured in 90 pregnant women, 30 in each trimester (age range 18-35 years) and a control group of age-matched non-pregnant women. Methods: total serum vitamin C concentration was measured using the 2.4-dinitrophenylhydrazine method which involves the conversion of vitamin C to dehydroascorbic acid in the presence of copper (II) ions and subsequent measurement of the resulting bishydrazone at 540nm. Results: the total vitamin C concentration in the first trimester was 2.55 ± 0.82 mg/dl and 2.32 ± 0.40 mg/dl and 0.77 ± 0.10 mg/dl in the second and third trimesters respectively. Relative to serum total vitamin C concentration in the controls (3.15 ± 0.13 mg/dl) these values are significantly lower (p < 0.05). Conclusions: low serum vitamin C in pregnancy may indicate utilization of this vitamin to mop up the excess reactive oxygen species and maintain its normal homeostasis. Therefore, Vitamin C supplementation during pregnancy is recommended in order to boost the body's low vitamin C level and prevent the predisposition to low birth weight babies, premature delivery and pre-eclamsia all of which are known to be associated with sub-optimal vitamin C levels during pregnancy.


Palavras-chave Gravidez, Vitamina C, Mulheres,
Espécies de oxigênio reativas asthma, renal disease and cancer.30 age and agematched non-pregnant adult females were also enrolled for comparative control studies.
Assay for serum vitamin C. Serum L-ascorbic acid was assayed using the 2, 4-dinitrophenyhydrazine method which measures total vitamin C concentration by oxidizing all vitamin C vitamers to dehydroascorbic acid in the presence of copper ions and subsequent measurement of the dehydroascorbic acid-bis-hydrazone derivative at 540nm. 16he study was conducted in compliance with the Declaration on the Rights of the Patient. 17ata are presented as mean ± SEM.Data analysis was done using the Minitab-10 Statistical Software.Mean serum vitamin C concentration among trimesters was compared using One-Way ANOVA.The method of Least Significant Difference (LSD) was used to assess for significant differences between means after the ANOVA; p values <0.05 were considered significant.

Results
Total serum vitamin C concentration in the three trimesters of pregnancy (mg/dl).
The results obtained are shown in Table 1.The mean serum concentrations of vitamin C in all the three trimesters were lower than the control.Average total vitamin C concentration in the first trimester was 20 % less than the control vitamin C concentration of 3.15 ± 0.13 mg/dl, (p <0.05).Total vitamin C concentration in the second trimester was 26 % less than the control concentration (p <0.05).The largest decrease was found in the third trimester, with a 75% drop relative to the control serum total vitamin C concentration (p <0.05).
Pregnancy is typically characterized by dynamic changes in multiple body systems, leading to an increase in basal oxygen consumption and changes in energy substrate use by different organs, including the fetoplacental unit. 1 From early pregnancy, the placenta influences metabolism, particularly energy homeostasis. 25] To meet this increased energy requirement during pregnancy, the human placenta is highly vascularized and sufficiently exposed to high maternal oxygen partial pressure. 6he consequent accelerated intake and utilization of oxygen and the increased activity of the mitochondrial electron transport chain leads to the generation of high levels of reactive oxygen species (ROS) and an accompanying elevated level of oxidative stress. 7umerous evidence abound confirming the excessive production of reactive oxygen species and other reactive species during both normal and abnormal pregnancy .8-9Morris et al. 10 reported high circulating levels of lipid peroxides in normal pregnancy and pre-eclampsia.4][15] Because of the abundance of reactive oxygen species during pregnancy, this work was aimed at measuring the serum concentration of total vitamin C in the three trimesters of pregnancy considering the important role of this vitamin in the scavenging of reactive oxygen species and maintenance of healthy pregnancy.

Methods
The subjects enrolled in this study comprised 90 pregnant women, all attending the Antenatal Outpatient Pediatric Department (OPD) of the Department of Obstetrics and Gynecology, Bauchi State Specialist Hospital.The 90 subjects comprised three groups of 30 individuals per trimester and characterized as having low risk, uncomplicated pregnancy.All the study subjects were within the age range of 18-35 years.Exclusion criteria included diabetes mellitus, pregnancy toxemia, hypertension, earlier reports of reduced levels of antioxidant nutrients in pregnancy. 23Since the lowest serum vitamin C concentration was found in the third trimester, it indicates that oxidative stress is highest during this trimester of pregnancy.This therefore underscores the need for vitamin C supplementations throughout the entire period of pregnancy since mean serum vitamin C concentration in all the three trimesters are significantly lower than normal, control values.It also corroborates the clinical evidence for the unequivocal benefits of antioxidant supplementation to protect against excessive reactive oxygen species during pregnancy. 7Vitamin C supplementation is particularly important in pregnant women as its deficiency has been shown to affect placental structure and facilitates placental infection both of which results in increased risk of premature rupture of placental membranes and premature births. 2,24

Discussion
As noted earlier, human pregnancy is associated with increased requirement for dietary energy as a result of an elevated metabolic rate 3 due chiefly to increased oxygen consumption and subsequent utilization.The accelerated oxygen intake has been shown to lead to increased levels of oxidative stress via production of highly toxic reactive oxygen species. 182] The progressive decline in serum vitamin C concentration observed in this study could indicate an increased utilization of the vitamin by pregnant women to maintain normal reactive oxygen species homeostasis by using the vitamin to mop up the excess reactive oxygen species produced during the pregnancy state.This finding further supports

Table 1
Total serum vitamin C concentration in the three trimesters of pregnancy (mg/dl).