Early intervention and appropriate treatment in patients with GDM or at increased risk for developing of GDM will helpful in preventing the adverse maternal and fetal outcome and also protect them from long term complications. GDM induces similar biochemical changes that are produced by DM outside pregnancy. Hyperuricemia has been used as a marker in the prediction of type 2 DM. Several studies have shown the association of hyperuricemia with GDM.
This study conducted in Mahatma Gandhi Medical Collage and Research Institute, Pondicherry, a tertiary care center between November 2010 and May 2012, was undertaken to find out the association of elevated first trimester uric acid with development of GDM. A total of 70 pregnant women were included and various parameters were studied.
The maternal age in this study ranged between 18 and 35 years. The mean age was 25.33±4.47. Majority (48.6%) of them were between 21 to 25 years of age. There was no statistical significance between age of the pregnant women studied and their serum uric acid level at <15 weeks of gestation (P = 0.704). There was no significant correlation between the age group and GDM (P = 0.643).
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The incidence of GDM with relation to age was low in this study population as majority of the subjects were in the low risk age group for the development of GDM. Lao TT et al and Khatun N et al have shown that advanced maternal age is a known risk factor for the pregnancy complications including preterm delivery, low birth weight, perinatal death, GDM, gestational hypertension, placenta previa, intra-uterine growth retardation (IUGR) etc.80, 81Yet another reason for lower incidence of GDM may be due to the smaller study population.
In this study 51.4% were primigravida and 48.6% were multigravida. There was no difference between the parity and serum uric acid levels at<15 weeks of gestation (P=0.538). The same has been shown by Dunlop W et al in 2005 in their study; (Effect of renal handling of uric acid in pregnancy) that there was no difference detected in the changes seen in serum uric acid levels between primigravida and multigravida. A Study by Nagalakshmi C.S et al has shown an increased risk of developing GDM among primigravida.77 Al-Rowaily MA et al have shown in their study that multiparous women were 8.29 times more likely to have GDM than nulliparous women.78 However, after adjustment for maternal age and history of abortion, nulliparous women were 2.95 times more likely to develop GDM than parous women. In this study there was no difference in the incidence of GDM in relation to the parity of the population studied (P = 0.870), the risk of development of GDM is almost equal in both primi and multiparous women. This may be attributed to the lesser population of pregnant women studied and the diagnostic test used for screening (one step test as per DIPSI).
80% of pregnant women studied were non obese (BMI <30kg/m2) and majority of them had their serum uric acid level in the second and third quartile. 20% were obese with their serum uric acid level in the third quartile followed by second quartile. This distribution has shown that there is a proportional increase in the serum uric acid with increase in the BMI but not statistically significant. There has also been noted a significant correlation between BMI and risk of development of GDM (P = 0.001).
In this study those subjects who had a normal BMI had elevated levels of uric acid at < 15 week of gestation which was associated with increased levels of blood glucose level at 24 to 28 weeks of gestation. These findings suggested though BMI is significantly associated with development of GDM, the association between elevated uric acid levels at early trimester and risk of development of GDM was independent of BMI. Similar statement was given by Laughon. KS et al that although uric acid was strongly associated with body mass index, the risk of gestational diabetes was increased among women with elevated first trimester uric acid independent of BMI.14
Majority of the subjects had no significant family history of DM though they had higher levels blood glucose at 24 to 28 weeks. There was a moderate significance noted between the family history of DM and one step test (P =0.048). Similar findings were noted in yet another study by Ratnakaran R et al where they have shown that established risk factors for GDM were relevant in women with family history of DM but may not be the principal determinants of gestational hyperglycaemia in women without significant family history.79 The serum uric acid levels at <15 weeks of gestation were not related to the family history of DM (p = 0.236) though the serum uric acid levels of 50% of those with significant family history were in the 3rd quartile.
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The subjects with uric acid in the first quartile had a normal one step test value (<120mg/dl). In the second quartile 27.1% had gestational glucose intolerance i.e. one step test of 120 to 140 mg/dl and 5.4% had GDM (>140mg.\/dl). In the third quartile 81.3% had gestation glucose intolerance and 12.5% had GDM. This distribution has revealed that higher level of serum uric acid in the first trimester were strongly associated with increased levels of one step test (120 to 140mg/dl) i.e Gestational Glucose Intolerance (GGI) (P=<0.001) though only 5.7% were diagnosed to have GDM.
The same was stated by Langhon KS et al first trimester hyperuricemia is associated with increased risk for development of GDM.14Wolak T el al also have shown that UA levels in the highest quartile of the normal range during the first 20 weeks of pregnancy are associated with higher risk for the development of GDM and mild preeclampsia.75 Zhou J et al showed in their study measured lipids and uric acid concentrations in 1000 healthy nulliparous women at 20 weeks of gestation and showed that hyperuricemic women experienced a 1.99-fold risk for preeclampsia and a 2.34-fold risk for GDM.76
Our findings are consistent with the association of uric acid with insulin resistance in the non-pregnant population10 and also the early pregnancy uric acid concentrations in our study were similar to those reported by others.
There was a significant correlation between the uric acid levels at <15 weeks and at 24 to 28 weeks (P=<0.001).Majority of the subjects did not have any changes between serum uric acid levels at <15 weeks and at 24 to 28 weeks of gestation. They either had same levels or slight increase in the level. This could have been due do the normal changes that occur in uric acid levels in pregnancy as stated by Boyle JA et al that the uric acid level fall during the early and mid-trimester rises to normal values in late pregnancy.73
There was no significant correlation between uric acid levels at 24 to 28 weeks and risk of development of GDM (P=0.094). Though there is a significant correlation between serum uric acid at <15 weeks and at 24 to 28 weeks, serum uric acid at <15 weeks of gestation is a better predictor of GGI and GDM than uric acid levels at 24 to 28 weeks of gestation (Pearson's correlation = 0.735). This is due to the fact that serum uric acid levels normally falls in early trimester and mid-trimester and rises to normal values in late pregnancy. Elevated or higher normal levels of serum uric acid in the first trimester may be associated with a pre-existing metabolic derangement which leads to poor maternal physiological adaptations and predisposes the pregnant women to development of pregnancy complications like GDM, pre eclampsia etc.
The sample size of this study was less due to the limited study period. In this study majority of subjects with high first trimester uric acid had one step test value of 120 to 140mg/dl (GGI). Follow up of these patients after 28 weeks of gestation was not done to find out whether they developed GDM later in the pregnancy.