Gestational diabetes mellitus (GDM) refers to glucose intolerance resulting in hyperglycemia which is founded during pregnancy for the first time (1). The prevalence of GDM varies across countries; its reported prevalence is 20% in Vietnam and Singapore (2), 11.1% in China (3), and 7.6% in the United States (4). Overall, the prevalence of GDM has been increasing worldwide (5), which significantly increases the rates of adverse pregnancy and birth outcome (6).
GDM also increases the long-term risk of type 2 diabetes mellitus (T2DM) and cardiovascular disease for mothers later in life (7). The risk of developing T2DM is over seven times higher (8) and the risk of developing hypertension and cardiovascular events is two times higher in women with previous GDM than without (9). Hyperglycemia is associated with increased risk of vascular endothelial injury and hypertension (10), which might interpret the mechanism of the high risk of both T2DM and cardiovascular disease among this population. More studies on glycemic status and cardiovascular health after delivery among this population are needed.
Hypertension is one of the main risk factors of cardiovascular disease (11). Nearly 40% of people aged 25 and over suffered from hypertension all over the world (12). High normal blood pressure, as an important predictor of hypertension (13), refers to systolic blood pressure (SBP) of 130–139 mm Hg and/or diastolic blood pressure (DBP) of 85–89 mm Hg (14). There was a study reporting that 53% of adults aged 65–94 years who had baseline clinical high normal blood pressure developed hypertension within four years in the United States (15).
The sex and gender framework emphasizes the collective impact and influence of biological and genetic factors as well as healthy social environment factors on health outcomes and conditions (16). Cardiovascular health as one of the most common health conditions, is determined by both sex (biological) and gender (sociocultural) factors (17). Several sex-related risk factors of developing hypertension in women with GDM, such as ethnicity and advanced age, have been identified. For example, Hispanic women with previous GDM tend to be easier to develop hypertension than Caucasian women (18). In Taiwan, compared with younger women with previous GDM, women at an advanced age had a higher risk for hypertension (19).
Obesity is another important sex factor for the development of cardiovascular disease and related conditions (20). Women with previous GDM are easier to be obese than women with normal glycemic status during pregnancy (21). Obesity-related variables, such as body mass index (BMI) and waist circumference, were associated with hypertension (22). BMI is inversely associated with high-density lipoprotein cholesterol, which positively correlates with the risk of developing hypertension (23).
Gender-related factors, such as health behaviors and psychosocial factors, are closely related to the development of hypertension (24). There is evidence showing that daily physical activity can decrease the risk of hypertension among women (25). Whereas, due to the responsibilities of taking care of children and senior in families for women in rural China, they rarely have time to do enough daily physical activity which is not equal to house work (26).
Diet is another important component of guidelines for antihypertensive therapy in America and Europe (27–29). Fruit and vegetable consumption is negatively associated with increased blood pressure (30). Compared with the nutrition-oriented Western diet, people prefer delicious food in China (31). With the improvement of the economy and social life, the consumption of animal foods and oil/fat has been increased (32). This could be a reason for the increased risk of developing hypertension among the general population. However, the impacts of physical activity and diet on increased blood pressure in rural Chinese women with previous GDM has rarely been reported.
Psychosocial factors also have an influence on the development of hypertension among general women. High levels of perceived stress positively correlate with increased blood pressure among women in France (33). Perceived stress refers to the degree to which people perceive that they cannot meet their needs (34). Further, work-related issues present challenges in balancing career and family responsibilities, which often disproportionately increase women’s mental stress (35). General self-efficacy refers to a person's confidence in achieving self-management and behavioral change (36). Health behaviors (e.g., healthy dietary habits and physical activity) can be improved by increasing their general self-efficacy among women with previous GDM (37). However, the contribution of general self-efficacy and perceived stress to increased blood pressure among women with previous GDM is not well documented.
To our knowledge, the long-term risk of hypertension and cardiovascular events in this population later in life has not been well recognized by nurses in China. There are few studies exploring the factors associating with increased blood pressure in women with previous GDM from both sex and gender perspectives. The aims of this study were (1) to describe the proportion of rural Chinese women with previous GDM developing increased blood pressure within 4 years after delivery and (2) to explore the association of sex-related factors (age, ethnicity, family history of hypertension, time since delivery, obesity-related factors [BMI and waist circumference], and blood glucose [FBG and 2 h-OGTT]) and gender factors (education, occupation, income, health behaviors [physical activity, vegetable and fruit intake, and sedentary time], and psychosocial factors [stress and general self-efficacy]) with the increased blood pressure.