A Comparative Study to Evaluate the Association of Bisphenol-A in Gestational Diabetes Mellitus as Compared to Pregnant Women with Normal Glucose Tolerance

Abstract

Introduction:

Gestational diabetes mellitus (GDM) is a frequent pregnancy complication. Increasing evidence suggests that environmental factors, such as exposure to Bisphenol A (BPA), may contribute to the development of GDM. This study aims to evaluate the association between BPA exposure and GDM in an Indian population.

Methods:

This observational, cross-sectional study was conducted at the outpatient clinics of the Department of Medicine and Department of Obstetrics and Gynecology and in collaboration with the Department of Biochemistry at a tertiary care and teaching hospital in North India. The study included 161 pregnant women divided into two groups: those with GDM and those with normal oral glucose tolerance test (OGTT). Participants’ urinary BPA levels were measured, and statistical analyses were performed to determine correlations between urinary BPA levels and GDM.

Results:

The mean urinary BPA level was significantly higher in the GDM group (41.17 μg/L) compared to the non-GDM group (14.19 μg/L), with a P value <0.01. Correlation analysis showed a strong positive association between BPA levels and OGTT results in the GDM group. The linear correlation graph formula y = 1.7443x + 168.84 can predict urinary BPA level based on OGTT glucose level.

Conclusion:

The study underscores the significant association between elevated urine BPA level and GDM, suggesting that BPA exposure may be a risk factor for this condition. Compared to previous studies, our research highlights the specific impact of BPA on GDM in the Indian context. The results advocate for reducing BPA exposure to mitigate the risk of GDM and related metabolic disorders.

INTRODUCTION

Gestational diabetes mellitus (GDM) is a state of impaired glucose tolerance first identified during pregnancy, specifically after 20 weeks of gestation.[1,2] It is one among the frequent complications encountered during pregnancy and affects both fetal and maternal health significantly.[1,2] Notably, most states in India have reported an increasing prevalence of GDM with Arunachal Pradesh being an exception showing a decline from 1.61% in 2015–16 to 0.87% in 2019–21.[3] The prevalence of GDM varies across different regions from 9% to 16% with urban areas experiencing a higher rate (17.8%) compared to semi-urban (13.8%) and rural areas (9.9%).[3] Several factors contribute to the rise in prevalence of GDM, including the growing number of women in child bearing age, higher maternal age, overweight and obesity, urbanisation, physical inactivity, polycystic ovarian syndrome (PCOS), history of previous GDM, and family history of diabetes.[4,5,6,7]

GDM possesses significant health risks for both mother and foetus. Maternal risks include polyhydramnios, infections, pre-eclampsia, prolonged labour, obstructed labour, progressive retinopathy, caesarean section, uterine atony, and postpartum haemorrhage.[8,9,10,11,12] Foetal risks include spontaneous abortions, macrosomia, congenital malformations, shoulder dystocia, intrauterine mortality, still birth, neonatal hypoglycaemia, and respiratory distress syndrome. Additionally, GDM contributes significantly to the non-communicable disease burden because of its long-term clinical effects.[13,14,15]

While several metabolic, genetic, and environmental factors are significant, the precise aetiology of GDM remains unclear. Bisphenol A (BPA) is a chemical widely used in industrial production of plastic; however, it may increase risk of diabetes and other health complications.

MATERIALS AND METHODS

This was a hospital-based observational, cross-sectional study which was conducted at the outpatient clinics of Department of Medicine and Department of Obstetrics and Gynecology and in collaboration with the Department of Biochemistry at a tertiary care and teaching hospital in India from July 2023 to June 2024. Participants were selected based on specific criteria: They were non-smokers and non-alcohol consumers, with normal blood pressure and lipid profiles. The inclusion criteria for the study were pregnant females either with GDM or with normal oral glucose tolerance test, aged over 18 years, with normal kidney and liver function, and normal thyroid function. Exclusion criteria included patients with diagnosed type 2 diabetes mellitus with pregnancy, pregnant females with comorbidities such as PCOS (who had been diagnosed with PCOS based on abdominal ultrasonography at any point prenatally), or metabolic syndrome, those who conceived via in vitro fertilization (IVF) or assisted reproductive technology (ART), and females with urine tract infections.

A total of 161 participants were included in the study based on a GDM prevalence of 11.8% and an acceptable sample error of 5%. Participants who met the inclusion and exclusion criteria were enrolled, and detailed history and physical examination were conducted. Blood and urine samples were collected.

A total of 161 participants were divided into two groups: 1. Cases (pregnant females with gestational diabetes mellitus, diagnosed following Diabetes in Pregnancy Study Group in India criteria) and 2. Controls (pregnant females with normal oral glucose tolerance test) as 89 and 72, respectively. From each participant, a total of 3 ml blood was taken, 2 ml in a red top vial for estimation of serum urea and creatinine and 1 ml in sodium fluoride vial for OGTT. 10 ml of urine was collected from each patient in a polypropylene tube for estimation of urine BPA levels. Urine sample was stored at -20 degree celsius. 1 mL urine sample was taken after thawing at room temperature. To maintain the pH at 2.5, we used appropriate amounts of acetic acid. After gentle mixing with the help of a vortexer, total BPA was extracted by using the phase-transfer extraction method. 1 mL of methyl-tertiary butyl ether was used for proper extraction followed by gentle vortexing. Then it was centrifuged at 14000 rpm for 10 min. After centrifugation, the upper layer of organic solvent was taken out and evaporated completely with the help of a nitrogen evaporator. Then, it was reconstituted with 1 mL of methanol and injected into LC-MS/MS (liquid chromatography with tandem mass spectroscopy).

Statistical analysis: The collected data were organised in a Microsoft Excel sheet and processed using SPSS version 25.0 (manufactured by IBM-International Business Machines Corporation) for analysis. Data were analysed using descriptive statistics, percentage, mean, standard deviation, Chi-square test, t–test, and regression analysis to determine the association between BPA levels and GDM. The data were represented in both tabular and graphical formats for clear visualisation and comparison. A two-tailed probability of P < 0.05 was considered statistically significant for all the statistical tests.

Ethical aspects

The study received ethical approval from the Institutional Ethics Committee, Sarojini Naidu Medical College, Agra (Reg No- ECR/1409/Inst/UP/2020). The approval letter number is SNMC/IEC/2024/226 issued on date 28/03/2024. Written informed consent was obtained from all participants for participation in the study and use of their data for research and educational purposes. The study was conducted in accordance with the ‘Declaration of Helsinki of 1964 and as revised thereafter’.

RESULTS

There were total 161 participants divided into two groups, 89 cases consisting of pregnant females with GDM and 72 controls consisting of pregnant females with normal OGTT. The mean age for cases was 28.33 with SD 5.1 years and that for control was 28.92 with SD 5.2 years, showing no significant difference between the groups (P = 0.471). The mean period of gestation in the case group was 26.34 ± 2.9 weeks and that in the control group was 26.47 ± 2.6 weeks, showing no significant difference (P = 0.756). Similarly, parameters like S. Urea and S. creatinine levels showed no significant difference between the two groups. Mean values of 2 h OGTT, Random blood glucose, and Urine BPA level were significantly higher in the case group compared to the control group. A summary of comparison of key demographic characteristics between the two groups is given in Table 1 and Figure 1.

Table 1.

Details of demographic characteristics of the two groups – cases and controls

Group statistics	Group	n	Mean	Std. Deviation
Age (years)	Case	89	28.33	5.11
	Control	72	28.92	5.21
Period of gestation (weeks)	Case	89	26.34	2.86
	Control	72	26.47	2.63
OGTT	Case	89	240.65	62.58
	Control	72	127.47	10.09
RBS	Case	89	171.29	37.26
	Control	72	109.33	9.46
OGTT	Case	89	240.65	62.58
	Control	72	127.47	10.09
Serum urea	Case	89	33.23	7.87
	Control	72	33.59	9.62
Serum creatinine	Case	89	0.88	0.23
	Control	72	0.91	0.16
Urine BPA (µg/L)	Case	89	41.17	22.86
	Control	72	14.19	5.23

Figure 1.

Comparison of Age, POG, OGTT, RBS, S. Urea, S. Creatinine, and Urine BPA levels between the two groups

On comparing mean Urine Bisphenol A (BPA) level and mean 2 hr OGTT blood glucose level of the lowest and highest quartile groups in both cases and controls, we found that the mean urine BPA level was 26.15% higher and the mean blood glucose level was 19.73% higher in the highest quartile in comparison to the lowest quartile in the control group; the mean urine BPA level was 30.70% higher, and the mean blood glucose level was 49.17% higher in the highest quartile in comparison to the lowest quartile in the case group [Table 2]. Overall, the mean BPA level was significantly higher in the case group (41.17 μg/L) compared to the control group (14.19 μg/L), with a P < 0.001 [Figure 2]. In the case group, regression analysis showed a strong positive correlation [correlation coefficient (r) =0.637] between mean urine BPA level and mean 2 h OGTT blood glucose level. The blood glucose level (Y) can be calculated from the value of urine BPA level (X) with the regression equation Y = 1.7443X + 168.84 [Figure 3].

Table 2.

Mean Urine Bisphenol A and mean 2 h OGTT Blood Glucose Level in cases vs controls (lowest and highest quartile)

Group	Mean Urine BPA Level (Lowest Quartile)	Mean Urine BPA Levels (Highest Quartile)	Difference (Δ)	Difference Percentage	Mean OGTT Blood Glucose Level (lowest quartile)	Mean OGTT Blood Glucose Level (highest quartile)	Difference (Δ)	Difference Percentage
Non-GDM	12.47	16.88	4.42	26.15%	98	122.1	24.1	19.73%
GDM	35.77	51.58	15.81	30.70%	165.18	324.97	159.79	49.17%

Figure 2.

Comparison of mean urine BPA level and mean 2 h OGTT blood glucose level in cases and controls

Figure 3.

Linear correlation of 2 h OGTT blood glucose level and urine BPA level in patients with GDM

DISCUSSION

BPA is a chemical widely used in industrial production of plastics to prevent corrosion and food spoilage, extending shelf life and ensuring food safety. However, it may increase risk of diabetes and other health complications. BPA exhibits oestrogenic activity by binding to oestrogen receptors with higher affinity for ERβ compared to ERα and can significantly impact cellular processes through non-genomic pathways. Moreover, BPA exposure can lead to elevated 17β-estradiol levels and activation of Peroxisome Proliferator-Activated Receptor alpha (PPARα) contributing to metabolic disorders including obesity and diabetes.[16,17]

This study indicated a possible association between exposure to BPA and an increased risk of developing GDM. Despite extensive research on this link globally, considerable information remains unexplored in the Indian context. This study aimed to address this gap by comparing BPA levels in women with GDM to those with normal glucose tolerance test.

Our study was most probably first of its kind in India, and its findings contribute to a better understanding of the potential health impacts of exposure to BPA during pregnancy. By exploring the association between BPA and GDM, we hope to identify a previously unrecognised risk factor for this common pregnancy complication and inform strategies for prevention and early intervention. In our cross-sectional study, 161 pregnant females were divided into two groups: one with GDM and another with normal OGTT. The mean urine BPA levels in the GDM group were 41.17 μg/L compared to 14.19 μg/L in the control group. Higher urine BPA levels were significantly correlated with higher OGTT levels. A linear correlation graph was generated, revealing a positive relationship between x and y, described by the equation y = 1.7443x + 168.84, which can help predict urine BPA levels based on blood glucose levels in GDM cases. Urine BPA levels were quantified in pregnant women during the second and third trimesters, highlighting higher levels of urine BPA in GDM females compared to non-GDM females. This suggests a significant association between elevated urine BPA levels and raised blood glucose levels.

We searched on Google Scholar and Pubmed Central, and we found epidemiological studies examining the effect of BPA exposure on blood glucose levels in pregnant women. A few of these studies emphasised the relationship between BPA and GDM, while some yielding null findings. One Chinese retrospective study found that higher urine BPA levels were associated with lower plasma glucose levels and reduced risk of GDM.[18]

Compared to Wenxin Zhang et al.[6] prospective cohort study, which included variables like weight and fetal sex, our study focussed on fewer variables. Zhang’s study suggested that urine BPA levels were higher in GDM with normal weight pregnant females and noted the impact of foetal sex on BPA levels. Similarly, Teppala S, Madhavan S, and Shankar A. analysed NHANES data from 2003 to 2008 and found a positive relationship between urine BPA and metabolic diseases, including diabetes and obesity.[17] Silver and colleagues observed comparable results in their analysis of combined NHANES data from 2003 to 2008, noting a significant increase in BPA exposure during this period.[15] Barbara Predieri et al.[19] case-control study in Sweden found that early and continued exposure to endocrine disruptors like BPA could have deleterious effects on infants and may lead to autoimmune diseases such as Type 1 Diabetes Mellitus (T1DM). A review of supplementary studies provided further insights, with conclusions outlined as follows [Table 3].

Table 3.

Review of supplementary studies with conclusions

Studies	Years	Conclusion
Lang IA et al.[14]	2003-2024	BPA may be linked to unfavourable health effects
LaKind JS et al.[16]	2008	No correlation between BPA exposure and diabetes
Wang X et al.[18]	Oct 2017	Higher maternal urine BPA concentrations were associated with reduced risk of GDM
Soomro MH et al.[20]	Aug 2024	BPA was not associated with GDM
Bellavia A et al.[21]	Apr 2018	BPA is associated with higher blood glucose level and higher 1st trimester BMI
Chiu YH et al.[22]	Apr 2017	BPA exposure during 2nd trimester associated with hyperglycaemia among sub-fertile women
Hou Y et al.[23]	Feb 2021	BPA exposure is not associated with GDM prevalence
Zhu Y et al.[24]	Dec 2020	Positive association of 1st trimester BPS concentration with GDM risk
Shapiro GD et al.[25]	Oct 2015	BPA exposure is not associated with GDM, but arsenic exposure has significant association
Martinez-Ibarra et al.[26]	July 2019	Unadjusted urine BPA concentration correlated with pre-gestational BMI
Filardi T et al.[27]	Feb 2020	BPA and pthalates are able to affect pregnancy and early foetal life
Yang Jiaqi et al.[28]	Oct 2020	BPA might affect glucose homeostasis and the middle term of pregnancy
Ensiyeh Taheri et al.[29]	Sep 2021	No association was found between BPA exposure and the risk of GDM/IGT

Limitations and future research

While the study gives valuable insights, it is important to recognise its limitations. Being a cross-sectional study with modest sample size may restrict the generalisation of its findings, highlighting the case for further investigation to confirm and expand upon these results.

CONCLUSION

BPA is a ubiquitous chemical used in plastic containers and canned food, known for its longevity in industrial products. Our study found a positive correlation between urine BPA levels and GDM, suggesting that reducing the use of plastic products containing BPA could help mitigate the burden of metabolic diseases. Previous studies had shown BPA’s harmful effects on children’s neurological development and its association with autoimmune diseases like T1DM. Further studies are needed to explore BPA’s endocrine-disrupting potential and its role in obesity, infertility, and diabetes and to establish regulations and scientific reviews on BPA use.

Author contributions

PKA: Concept, design, definition of intellectual content, literature search, clinical studies, data analysis, statistical analysis, manuscript preparation, manuscript editing and manuscript review. SSY: Design, literature search, data acquisition, data analysis, statistical analysis, manuscript preparation, manuscript editing and manuscript review. RG: Concept, design, literature search, data analysis, manuscript editing, manuscript review. KS: Clinical studies, data acquisition, data analysis, manuscript review. SKP: Literature search, data analysis, statistical analysis, manuscript preparation, manuscript editing and manuscript review. MRK: Clinical studies, data acquisition, data analysis, manuscript review. AG: Clinical studies, data analysis, manuscript review. NP: Literature search, data analysis, manuscript review. PG: Clinical studies, data analysis, manuscript review. GG: Clinical studies, data acquisition, manuscript review.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence

All the authors declare that artificial intelligence was not used in the manuscript writing or preparation.

Data availability

Data available on request from the corresponding author.

Funding Statement

Nil.