Gestational diabetes mellitus linked to early particle exposure with high BMI

The incidence of gestational diabetes mellitus (GDM) is rapidly increasing worldwide and affects up to one in six pregnant women. A new Primary Care Diabetes A review study relates this to a high body mass index (BMI) before the onset of pregnancy, associated with exposure to different levels of particles (PM) of a certain size.

Study: PM exposure in early pregnancy, prepregnancy adiposity, and risk of gestational diabetes mellitus in Finnish primiparous women: an observational cohort study. Image Credit: Ground Image/Shutterstock.com

Introduction

DG increases the risk of multiple adverse pregnancy effects that can affect both mother and fetus. Women who are older during pregnancy, who are obese, and who have a genetic background favoring the development of diabetes are at increased risk of GD, especially those who belong to non-white races.

Additionally, previous research suggests that the risk of GDM is higher following exposure to environmental pollution. Specifically, air pollution from inhalable particles appears to be a likely contributor; however, the associations are unclear, especially since a range of PM sizes are often present in a given environment.

About the study

In the current study, PM with a diameter of up to 2.5 μm (PM_2.5) and 10 μm (PM_ten) has been considered a potential risk factor for GDM. PM_2.5 occurs during the combustion of wood, while PM_ten occurs due to traffic raising dust brought by vehicles from industrial facilities and from the ground.

The researchers of the present study sought to determine whether the risk of DG varies with exposure to PM during the first trimester in women depending on the degree of body fat content before pregnancy.

A Finnish cohort of approximately 6200 women who gave birth for the first time between January 1, 2009 and December 31, 2015 was evaluated. The average age was 28.5 years with a BMI of about 24 before the start of pregnancy.

Average daily PM concentrations_2.5 and PM_ten were also assessed during this period to estimate exposure during the first trimester. More than one in seven women in the study cohort was diagnosed with GD.

What did the study show?

Average daily PM concentrations were low at around 7.9 μg/m3 for PM_2.5 and about 14.5 μg/m3 for PM_ten. These concentrations were comparable in primipara, regardless of the occurrence of GDM. Interestingly, these rates are lower than average urban concentrations of PM in urban areas of Europe, according to the World Health Organization (WHO).

During the first trimester, average daily MP_ten prepregnancy concentration and BMI independently increased the risk of GDM.”

The average daily concentration of PM_ten interacted significantly with prepregnancy BMI to increase the risk of GDM. This increase was observed even after compensating for age and smoking, despite the fact that about 20% of the women in the current study were smokers.

No interaction was observed between daily PM_2.5 concentration and BMI before pregnancy on the risk of GDM.

What are the implications?

The high prevalence of DG in this cohort contradicts the apparently low mean concentrations of PM. No association was observed between this exposure to either PM size and the risk of GDM during the first trimester in these primiparae. Conversely, when pre-pregnancy fat content was taken into account, this factor interacted with PM_ten concentration to demonstrate a positive association with GDM risk.

Some previous studies have shown that PM exposure is linked to insulin resistance, metabolic syndrome, and dyslipidemia, all of which are conditions that precede DG in many pregnant women. Even in healthy adults, air pollution is associated with a higher level of inflammation as assessed by C-reactive protein (CRP) levels, as well as in people with diabetes and those with DG. In fact, CRP is higher in women with glucose intolerance during pregnancy.

In animals, obesity due to dietary factors reinforces the diabetogenic effect of exposure to PM.

The findings of this study merit in-depth analysis given the solid and comprehensive data on which they are based. All women in Finland are screened by the standard 75g oral glucose tolerance test and have access to free prenatal care. Birth registration and weather data are also carefully and fully stored.

The observational design of the current study excludes the ability to take into account potentially confounding factors such as exercise, sleep and diet. Despite this, the study underscores the need for intervention, not only in prenatal care, but also in areas such as environmental health to reduce the number of cases of GDM and thus improve pregnancy outcomes.