iran can be divided into 11 regions with 28 provinces ( supplementary file ) , based on ethnographic , demographic , epidemiologic , and socioeconomic factors ( 18 ) .
this study was cross - sectional and was conducted during the year 2001 in iran .
it was a part of the micronutrient survey , which covered the whole country and was conducted by the ministry of health ( moh ) of iran .
the study population was households and the sampling method was unequal cluster sampling with unequal household sizes randomly selected throughout the country .
the clusters were sampled relative to the size of the urban and rural population of each province in all 11 regions .
there were 880 clusters in all 11 regions , 504 urban and 376 rural clusters .
before the study was conducted , a team of health workers in each health care center in urban and rural areas were selected .
each team was assigned to pick up at least five people for the study from each subregion .
pregnant women were informed about the study process . assigned pregnant women gave informed consent , and accepted to give blood samples and complete questionnaires .
these pregnant women were targeted in their own provinces by written invitation at the nearest health care center that belonged to their region .
if a woman was not able to go to the health care center within the due date , the survey staff would go to the woman 's house and invite her to participate in the study . as an inclusion criterion ,
it was important that the pregnant women were otherwise healthy and did not have any kind of chronic diseases such as diabetes or heart disease .
the total number of pregnant women who participated in the study was 4,368 from all regions of iran , but data on vitamin a levels were only available in 3,270 women .
a questionnaire was designed by the moh in iran to collect information about mothers on general characteristics , health status , supplements if used , number of abortions , pregnancies , and deliveries . from each participant ,
a minimum of 6.5 ml venous blood was collected and kept in dry ice and sent to an accredited district laboratory for centrifugation .
vitamin a was analyzed as retinol by using high - performance liquid chromatography ( hplc ) at the who collaborating laboratory in tehran after the samples were transported there in a cold chain vehicle .
data for 3,270 pregnant women were analyzed with spss version 17.0 ( spss inc . ,
one - way anova test was carried out to test the significant differences between the mean of vitamin a levels within groups with different age and gestational age .
one - way anova test was computed to test the significant difference of parity on vitamin a status . two - way anova test was carried out to test the impact of age and areas ( rural and urban ) on the levels of vitamin a in pregnant women .
the approval for this study was obtained from the ethics committee of the moh in iran .
data for 3,270 pregnant women were analyzed with spss version 17.0 ( spss inc . ,
one - way anova test was carried out to test the significant differences between the mean of vitamin a levels within groups with different age and gestational age .
one - way anova test was computed to test the significant difference of parity on vitamin a status . two - way anova test was carried out to test the impact of age and areas ( rural and urban ) on the levels of vitamin a in pregnant women .
the approval for this study was obtained from the ethics committee of the moh in iran .
the mean age of the participating women was 26 years , ranging from 14 to 47 years .
the number of included pregnant women in the 11 regions varied between 229 and 330 ( table 1 ) .
mean ( sd ) values of serum vitamin a ranged from 0.77 ( 0.46 ) to 1.12 ( 0.43 ) mol / l . in table 1 ,
the regional as well as national mean ( sd ) levels of vitamin a as well as prevalence rates within the categories deficient , insufficient , suboptimal , and optimal is shown .
mol / l ) are also shown . the highest mean plasma retinol level ( 1.12
mol / l [ 0.43 ] ) was found in central iran ( region 6 ) .
deficiency was mainly seen in regions 2 , 5 , 7 , 8 , and 11 .
mol / l for the whole nation is well above 20% ( 24.9% ) and should therefore be characterized as severe according to the who categories . in some parts of the country the prevalence below 0.7 mol
/ l is over 30% ( 3 , 11 ) with one region reaching the level of 45.9% ( 7 ) .
the mean ( sd ) of plasma retinol levels in pregnant women and the percentage distribution of deficient , insufficient , suboptimal , and optimal levels in fig .
1 , the percentage distribution of vitamin a status is shown for the 11 regions .
deficiency was mainly seen in regions 2 , 5 , 7 , 8 , and 11 .
the highest optimal percentage of vitamin a was in regions 2 , 4 , 6 , 9 , and 11 .
more than half of pregnant women had serum vitamin a with suboptimal level , while vitamin a deficiency was only seen in less than 7% of all pregnant women in the study , and insufficiency in 18% .
the mean ( sd ) vitamin a level in rural and urban areas were 0.98 ( 0.4 ) and 1.00 ( 0.4 ) mol / l , respectively .
vitamin a in each age group was slightly lower in rural than that in urban areas .
the difference showed that the difference of vitamin a in both areas was not statistically significant .
however , there was a statistically significant main effect of age on vitamin a level ( p=0.005 ) . using the same test , this effect size was rather small ( eta squared=0.003 ) ( fig .
2 ) . mean vitamin a in rural and urban areas at different gestational age groups .
vitamin a levels in pregnant women decreased by increasing maternal age ( anova , p=0.005 ) ( table 2 ) .
women who were less than 23 years old had higher levels of serum retinol than the older ones .
there was a weak negative but significant correlation between age and vitamin a status ( pearson correlation , r=0.047 , p=0.007 ) .
the meansd of vitamin a ( mol / l ) in pregnant women at different age groups p - value for the difference within the groups=0.008 , one - way anova test was performed .
p - value for the difference between the two defined groups=0.006 , post hoc anova test was performed .
the mean vitamin a decreased as the gestational age increased ( p=0.009 , one - way anova ) .
the mean serum retinol decreased as the gestational age increased ( p=0.009 , one - way anova ) .
meansd of vitamin a ( mol / l ) in pregnant women with different gestational age p=0.01 difference between two defined groups p=0.02 difference between two defined groups , post hoc test was performed .
there was no significant relation between parity and vitamin a status ( f=0.79 , p=0.45 ) as shown in table 4 .
meansd of vitamin a ( mol / l ) in pregnant women with different parity p=0.45 , one - way anova test was performed .
this study showed that pregnant women in 2001 in this nationally representative study from iran had a low vitamin a status since 25% of pregnant women had insufficient or deficient vitamin a levels . using the who cut - offs for national prevalence of vitamin a deficiency , iran should by this standard
be considered a country with severe vitamin a insufficiency prevalence ( < 0.7 mol / l ) in 2001 .
in contrast , reports from the north of iran , marand district , in 2002 showed that 2.1% of child - bearing women had a deficiency level of vitamin a ( < 0.7 mol / l ) but 18% had values between insufficient or suboptimal level of vitamin a ( 19 ) . prevalence of deficiency levels ( < 0.36
mol / l ) was 6.6% nation - wide and similar to the average global prevalence of maternal vitamin a deficiency in developing countries ( 7% ) ( 20 ) .
the highest prevalence of deficiency to our knowledge was reported from nepal ( 31% ) ( 21 ) , about five times higher than in iran .
china had the lowest prevalence of deficiency , only 2% in 2001 ( 21 , 22 ) .
in contrast , data from who in 2005 showed that on average 11.6% of pregnant women in europe had vitamin a deficiency , ranging from 2.6 to 20.6% over the past 15 years ( 10 ) .
maternal vitamin a deficiency was also correlated to a reduced intra - uterine growth rate and birth weight , and higher infant mortality ( 2325 ) .
the prevalence of vitamin a deficiency we found indicates a slight improvement in vitamin a status from severe to moderate deficiency during 1989 to 2001 ( 10 ) . a general severe deficiency of vitamin a in cord blood in male infants in 1989 developed into moderate deficiency in 2001 in iran ( 17 ) .
despite the improvement in prenatal health care facilities , which in the meanwhile have been organized in each province supplying multivitamin ( vitamins a+d ) supplements free of charge through the primary health care system .
supplementation of vitamin a to infants from 2 weeks of age until 2 years by moh in the past decades may be responsible for a previous finding that vitamin a deficiency and insufficiency were rare in infancy ( 18 ) .
the higher prevalence of insufficient vitamin a levels in the south of iran might be associated with lower contribution of animal and milk products to the total energy intake , being 6 and 1% , respectively , in comparison with central and north of iran , where animal and milk products contributed to about 8 and 4% , respectively , of the total energy intake ( 26 ) .
a low access in the south of iran to main sources of vitamin a ( dairy products , vegetables , and fruits ) may be related to the hot and dry climate in this region ( 27 ) .
one study in northwest of iran showed that the important sources of vitamin a in child - bearing women were nuts and green leaves , products that were not typical of other populations ( 19 ) .
vegetables and fruits provide carotenoids equivalent to more than 50% of vitamin a ( 4 ) .
moh reported that the  intake to need ratio of vitamin a shows a scattered provincial distribution , from 60% in sistanbalouchestanto to 100% in east azarbayejan ( 26 ) .
this is in accordance with the consumption of the main sources of vitamin a in the south of iran , that is , sistanbalouchestan is low ranking in both urban and rural areas .
this might also be related to socioeconomic status , drought , and low production of fruits and vegetables . referring to the un food and agriculture organization ( fao ) regarding the nutritional intake in iran ( 2002 ) , the average daily intake of vitamin a was lower in villages than in towns , but insufficient in both , based on lower intake of animal products , fruits , and vegetables ( 26 ) . in this study , the level of vitamin a deficiency was almost the same in both areas .
the association between the status of vitamin a and age has been reported earlier ( 10 , 21 ) and has been related to factors such as dietary patterns and life - style that influence the nutritional status ( 28 ) .
the current study revealed that there was a significant correlation between gestational age and serum retinol .
similarly , among nepalese pregnant women , even though the prevalence of vitamin a deficiency was higher only in late pregnancy , it lead to night blindness ( 9 ) . this might be explained by an increased vitamin a - transfer to the fetus during late pregnancy .
in contrast to our finding regarding the negative association of vitamin a with age , it has been reported elsewhere that night - blind women were more likely to be teenagers ; however , the risk again increased with age among women aged above 30 ( 9 ) .
the difference could be explained by the fact that the nepalese study reported data based on whether the women had night blindness during pregnancy or not , while our study reported serum retinol levels .
in addition , we had no records of the socioeconomic status which could be an influencing factor here , as it has been shown in the previously mentioned study ( 9 ) .
one study in bangladesh showed no correlation between parity and serum retinol ( 29 ) . a limitation to our study was that investigations at the regional level in the 11 included regions did not include data on sociodemographic differences .
this study illustrates that the status of vitamin a was good in 75% of pregnant women in iran . as
the who goal is to eliminate vitamin a deficiency globally , this study shows that iran has achieved a relatively good result historically in the drive to eliminate vitamin a deficiency only in some provinces but not at the national level .
since this data does not represent the current status of vitamin a in the country , further information on vitamin a status in pregnant women are required for a strict surveillance of this important problem and to ensure that the vitamin a status continues to improve in iran .
the authors have not received any funding or benefits from industry or elsewhere to conduct this study .
 backgroundvitamin a deficiency is considered as one of the public health problems among pregnant women worldwide . 
 population representative data on vitamin a status in pregnancy have not previously been published from iran.objectivesthe aim of this study was to publish data on vitamin a status in pregnant women in all the provinces of iran in 2001 , including urban and rural areas , and to describe the association of vitamin a status with maternal age , gestational age , and parity.designthis descriptive cross - sectional study was conducted on 3,270 healthy pregnant women from the entire country , 2,631 with gestational age 36 weeks , and 639 with gestational age > 36 weeks . 
 vitamin a status was determined in serum using high - performance liquid chromatography.resultretinol levels corresponding to deficiency were detected in 6.6% ( < 0.36 
 mol / l ) and 18% had insufficient vitamin a levels ( 0.36<0.7 
 mol / l ) . 
 suboptimal level of serum retinol was observed in 55.3% of the pregnant women ( 0.71.4 mol / l ) . only about 20% of the women had optimal values ( > 1.4 
 mol / l ) . 
 the level of serum retinol was lower in older pregnant women ( p=0.008 ) , and at higher gestational age ( p=0.009 ) . 
 high vitamin a levels were observed in pregnant women in the central areas of iran and the lowest values in those in the southern areas of iran.conclusionsthe vitamin a status was good in 2001 but should be closely monitored also in the future . about 25% of pregnant women had a vitamin a status diagnosed as insufficient or deficient ( < 0.7 mol / l ) . 
 the mean serum retinol decreased as the gestational age increased . 
 the clinical significance of this finding should be further investigated , followed by a careful risk group approach to supplementation during pregnancy . 
Methods
Statistical analysis
Ethical approval
Results
Discussion
Conclusions
Conflict of interest and funding