Elevated C-Reactive Protein (CRP) during First-Trimester For Gestational Diabetes Screening

Background: Studies investigating the impact of inflammatory factors on gestational diabetes mellitus (GDM) are extremely sparse. This study aimed to find out the association of inflammation as defined by C-reactive protein (CRP) with gestational diabetes. Methods: This prospective cohort study, conducted in Patel Hospital Karachi from September 2020 to February 2021, enrolled 172 healthy gravid women at ≤ 10 weeks of pregnancy. A structured proforma was used to record age, education, past medical and obstetric history (parity, number of miscarriages, mode of deliveries, gestational age), blood pressure, height, and weight of all patients. Serum concentration of CRP and levels >1mg/dl was considered high. Oral glucose tolerance test was performed at 24-28 weeks to diagnose GDM. Data was analysed by using SPSS and Chi-squared test was applied to compare the difference between groups with, and without diabetes and p-value ≤ 0.05 was considered significant Results: Total 93 patients had raised CRP of which 8(4.6%) developed GDM (p<0.00001). Advanced age (p=0.00042) and weight (p<0.00001) were found to be independent risk factors. It was observed that CRP levels rise with increasing weight (p=0.0095) however, parity and blood pressure had no effect on GDM development. Women who had diabetes had higher BMI (<0.00001) showing that increasing weight was an independent risk factor. The sensitivity and specificity of CRP in detecting GDM was 100% and 48.17%. Conclusion: Raised C-reactive protein levels in first trimester can lead to subsequent development of hyperglycaemia of pregnancy and thus can be considered as an easy and simple screening test for GDM.


INTRODUCTION
Gestational Diabetes Mellitus (GDM) is defined as hyperglycaemia that is first recognized in the second or third trimester of pregnancy in women with previous normal sugar levels and can lead to numerous adverse outcomes for mother and baby 1,2 . GDM prevalence varies across the world affecting almost 7-10% of pregnancies worldwide [3][4][5] . The sooner the disease is detected in pregnancy the better would be the outcome. Women who had a history of hyperglycaemia in pregnancy have an increased chance of getting adult onset diabetes later on in life 2 .
Diabetes of pregnancy is more prevalent in women who are above 30 years, overweight or obese, have diabetes in family, previous history of stillbirth or anomalous baby and have gestational diabetes in the previous pregnancy 2 . GDM screening tests are done after assessing risk factors. There is increase insulin resistance in pregnancy making it a diabetogenic condition 2 . Insulin resistance is linked with inflammatory conditions and the development of type 2 diabetes. It is shown by several studies that increased inflammation as measured by CRP is an independent risk factor for the development of diabetes 6 .
Although pregnancy itself is an anti-inflammatory condition, there is an increased level of inflammation during the early stage of pregnancy such as during implantation leading to increasing levels of various inflammatory mediators 7 . High maternal CRP is associated with miscarriage, premature labour and rupture of membranes, toxemia of pregnancy, fetal growth restriction and chorioamnionitis 8,9 . The possible mechanism by which inflammation leading to diabetes could be the increase blood sugar and glycosylated haemoglobin levels (HbA1c) causing the release of CRP 10 . In addition, obesity, which is a risk factor for GDM, causes an increase release of pro-inflammatory cytokines from adipocytes 6 . Currently, it is being hypothesized systemic inflammation may be involved in the establishment of GDM 11 . Early diagnosis and treatment are very crucial to prevent maternal and neonatal adverse outcome. Therefore, this study was performed to define the role of CRP in the screening of gestational diabetes.

METHODS
It was a prospective cohort study conducted from September 2020 until February 2021. A total number of 172 pregnant patients attending antenatal checkups in Department of Obstetrics and Gynaecology of Patel Hospital, Karachi were selected. All pregnant women18-35 years with single fetus less than 10 weeks of gestation based on their last menstrual period were included in the study after written informed consent. All patients were ensured about the confidentiality of identity and were given free choice of withdrawing from the study at any point. Ethical approval was obtained from the institutional ethic committee (Ref no.102/2020).
A structured proforma was used to record age, education, past medical and obstetric history (parity, number of miscarriages, mode of deliveries, gestational age), blood pressure, height, and weight of all patients at booking. Patients with previous history of hyperglycaemia in pregnancy, pre-existing or family history of diabetes, random blood sugar (RBS) of more than 140mg/dl, history of macrosomia, stillbirth, recurrent miscarriage, hypertension and polycystic ovarian syndrome were excluded from the study. Patients with chronic hypertension, thyroid disorder, chronic kidney disease, cardiovascular disease, autoimmune and chronic inflammatory disease, current active infection, antibiotic use within two weeks before sampling, seasonal allergy and those taking corticosteroids or non-steroidal anti-inflammatory drugs were also excluded.
The blood sample was taken for serum CRP in addition to the standard antenatal tests from all patients in the first trimester. Participants were followed up until 24-28 week of pregnancy and 75g oral glucose tolerance test (OGTT) was carried out at that time. CRP level was measured by latex agglutination semi-quantitative test kit. CRP > 1mg/dl was considered raised. Gestational diabetes was diagnosed by Hyperglycaemia and Adverse Pregnancy Outcome (HAPO) criteria (fasting blood glucose ≥92mg/dl, 1-hour ≥180mg/dl, 2-hour ≥153mg/dl) 12 .
Data were analyzed by using SPSS version 22. Mean, standard deviation and frequency table was used for data presentation. Chi-square test was used to compare the difference between groups with and without diabetes. The 2 × 2 contingency table was used for calculating sensitivity, specificity, positive predictive value, negative predictive value and accuracy. The level of significance was kept at p-value ≤ 0.05.

RESULTS
The average age of patients was 26.5±5.33 years and mean gestation of pregnancy was 7.5±1.87 weeks. The majority of participants were multipara (74.41%), educated (72.6%) and working women (76.1%). The average body mass index was 24.03±3.83 kg/m 2 . The mean random blood sugar was 99.5±22.7mg/dl. The association of CRP and GDM with baseline characteristics is shown in Table 1.
Out of 172 patients, ninety-three had raised CRP of which 8(8.6%) developed GDM (p<0.00001) showing a significant association between high serum C reactive protein and gestational diabetes as shown in Figure 1. It is shown in Table 2 that with increasing levels of CRP the risk of GDM also increases.  It was found that CRP levels rise with increasing weight (p=0.0095) indicating that CRP level is independently related to BMI which can be seen in Figure 2. The risk of GDM increased with advance maternal age (p=0.00042). However, parity and blood pressure had no effect on GDM development. It was also found in our study that women who had diabetes were of higher Body mass index (BMI) (<0.00001) Table 1. Thus, it was showing that increasing weight was an independent risk factor for GDM as shown in Figure 2.

Variables
The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CRP in detecting GDM was 100%, 48.17%, 8.6%, 100% and 50.58% respectively as shown in Table 3.

X-axis: Number of patients, Y-axis: Body mass index (BMI kg/m 2 ).
PPV: Positive Predictive Value, NPV: Negative Predictive Value, CI: Confidence Interval. showing that high C-reactive protein can result in GDM. This is inconsistency with previous research studies 13,14 . Increased levels of CRP in the blood can lead to hyperglycaemia by influencing insulin resistance 15 . It has been shown in others studies that elevated CRP levels in blood have a notable relation with subsequent development of hyperglycaemia of pregnancy 16 . Patients with gestational diabetes tend to have higher CRP levels as compared to normal pregnant women 16 . Hence, quantitative C-reactive protein level is an acceptable test in predicting diabetes in pregnancy 17 . In contrast to the above, the studies by Corcoran and Korkmazer showed no association between CRP and GDM 18,19 . Gestational diabetes resolves spontaneously after delivery but is linked to complications in both mother and the newborn 21 . It has been proven that intrauterine exposure to maternal GDM can lead to glucose intolerance, obesity and type 2 diabetes in offspring 22 . Recently, there has been an increased interest to disclose the role of inflammation in GDM development. In a previous study, increased levels of CRP and IL-6 were observed in pregnant women with glucose intolerance and GDM. Thus, suggesting that these may have a role in the pathophysiology of glucose intolerance and can serve as potential serum markers for the early screening of glucose intolerance 23 . Furthermore, there is an elevated inflammatory response with increasing age and BMI and has a significant association with GDM and inflammatory response is observed with increases in both age and BMI 24 . Studies have suggested that there is strong correlation between body fat mass and serum CRP levels 24 . Obesity has been identified as a predictor of elevated CRP, which is a risk factor for cardiovascular and coronary heart disease 25 . Furthermore, C-reactive protein was highly correlated with body mass index in some previous research studies 6 . In the current study it was observed that patients with high BMI tend to have increased CRP levels (p=<0.0095) and there was a remarkable correlation between GDM and obesity (p=<0.00001).

Figure 2: Association of body mass index (BMI) with C-reactive protein (CRP) levels and gestational diabetes (GDM).
Seeing that it is known that inflammation can cause diabetes in pregnancy by causing insulin resistance 6 . The increase in blood sugar levels accelerates the synthesis of glycosylated haemoglobin and the expression of macrophages thus causing the release of inflammatory markers like CRP 10 . CRP is a commonly available laboratory test and if combined with maternal risk factors as assessed by history and demographic features, can be predictive of GDM 11 . Thus, it helps in identification of those patients who are at higher risk of developing hyperglycaemia of pregnancy as early as in the first trimester.
Recognizing these patients earlier can help in better maternal and neonatal outcomes by intervening through treatment and lifestyle modification.
However, a single measurement of serum CRP level does not provide a measure of maternal inflammation status. Besides, C reactive protein levels rise during normal pregnancy 15 . Further comprehensive studies are needed to assess diagnostic accuracy of serum CRP in GDM screening. In addition, inflammatory cytokine levels fluctuate throughout pregnancy. Therefore, the levels should be monitored multiple times for finding a specific correlation between inflammation and GDM or glucose intolerance.

CONCLUSION
Women with hyperglycaemia of pregnancy have increased inflammatory reactions during the first trimester. C reactive protein measurement could be a useful screening test in the first-trimester for the prediction of GDM. CRP test can be a new, fast and reliable screening test for GDM screening. However, further research studies are needed to strengthen these findings. It is easy to measure and can predict the risk of other pregnancy complications as well such as preeclampsia, preterm labour, intrauterine growth restriction etc. allowing better surveillance during gestation.

AKNOWLEDGEMENTS
Special thanks to Dr. Tashmina Taha and Dr. Durriya Rehmani for their help in sample collection.

CONFLICT OF INTEREST
There is no conflict of interest.

ETHICS APPROVAL
The ethical board of Patel Hospital (Ref no.102/2020) approved the following study.

PATIENTS CONSENT
Verbal and written informed consents were obtained from all patients.

AUTHORS' CONTRIBUTION
SY was involved in randomization of patients, data collection and analysis, literature review, discussion, results and reference writing and authored the manuscript.