Gestational diabetes and preeclampsia

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Abstract

Objective: To determine whether gestational diabetes mellitus (GDM) increases the risk for preeclampsia independent of other risk factors. Study design: The association between GDM and preeclampsia was analyzed in a population of women who had given birth to singletons registered in Swedish Medical Birth Register from 1992 through 1996 (n=430,852). Results: GDM occurred in 0.8% and preeclampsia in 2.9% of all pregnancies. The rate of preeclampsia was higher in the GDM than in the non-GDM group (6.1% versus 2.8%). High age, nullipara, chronic hypertension, kidney disease, and high body mass index (BMI) were all independently associated with increased risk for preeclampsia. Smoking was associated with decreased risk. Adjusted odds ratio for GDM as a risk factor for preeclampsia was 1.61 (95% confidence interval (CI) 1.39–1.86) when prepregnancy BMI, which was a true confounder, was included in the last step of the multiple logistic regression analysis. Conclusions: There is an independent and significant association between GDM and preeclampsia. Obesity is a major confounding factor but could not explain the total excess risk.

Introduction

Preeclampsia is a major complication of pregnancy, and is associated with increased maternal and fetal mortality and morbidity. The rate of preeclampsia is significantly higher in type 1-diabetic pregnancies than in pregnancies in the population at large [1], [2]. Several authors have also reported an increased or a tendency to an increased frequency in gestational-diabetic pregnancies [3], [4], [5], [6], [7], while others have found a normal rate [8].

Women with gestational diabetes mellitus (GDM) constitute a heterogeneous group in many respects. For example, they differ with regard to the degree of impairment of glucose metabolism and its time of onset during pregnancy. Furthermore, women with GDM are often characterized by older age and obesity, factors that may be associated with preeclampsia [6]. From an epidemiological point of view, the importance has been emphasized of considering the influence of other variables than glucose tolerance when evaluating the maternal and fetal outcome among women with GDM [9]. Factors contributing to conflicting results may be small study populations and lack of information about potential confounders. The availability of the Swedish Medical Birth Register (MBR) makes it possible to analyze the association between gestational diabetes and preeclampsia in a large population and scrutinize the possible influence of several confounding risk factors.

The aim of this study was to determine whether GDM increases the risk for preeclampsia independently of other risk factors.

Section snippets

Subjects and methods

In Sweden, almost every pregnant woman visits an antenatal care unit [10]. Information about the pregnancy and its outcome is collected prospectively in the MBR from the first antenatal visit. The register covers more than 99% of all births in Sweden [11], and includes a wide range of data concerning the pregnancy, mother, and infant, e.g., the mother’s age, obesity, smoking habits, parity, and diseases and information about pregnancy complications, the delivery, and neonatal complications. The

Results

GDM occurred in 3448 (0.8%) and preeclampsia in 12,005 (2.9%) of all pregnancies (n=430,852). There was a higher rate of preeclampsia in the GDM group than in the group without GDM (6.1 and 2.8%, respectively). The distributions of maternal characteristics among women with and without GDM and the rates of preeclampsia are presented in Table 1. Higher age, BMI, parity, and occurrence of pre-pregnancy chronic hypertension characterized the GDM mothers, while smoking habits and pre-existing kidney

Comments

The result from this population-based study of more than 400,000 pregnant women clearly demonstrates that GDM is independently associated with an increased risk of preeclampsia. Women with GDM, are characterized by increased insulin resistance and/or defective insulin secretion [13]. Recent studies also support an association between preeclampsia and increased insulin resistance [14], [15], [16], [17]. The etiology of preeclampsia is still not clearly established. It probably has a

Acknowledgements

This study was supported by grants from The Physician’s Day Foundation of The Örebro Society of Medicine, and the Research Committee of Örebro County Council, Örebro, Sweden.

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