Abstract
In the face of the obesity epidemic around the world, attention should be focused on the role of maternal obesity in the development of pregnancy. The purpose of this analysis was to evaluate the prediction of preeclampsia (PE) and isolated gestational hypertension (GH) for a number of maternal factors, in order to investigate the importance of pre-pregnancy obesity (body mass index, BMI ≥ 30 kg/m2), compared to other risk factors (e.g., prior PE, pregnancy weight gain (GWG), infertility treatment, interpregnancy interval, family history, the lack of vitamin supplementation, urogenital infection, and socioeconomic factors). In total, 912 women without chronic diseases were examined in a Polish prospective cohort of women with a singleton pregnancy (recruited in 2015–2016). Separate analyses were performed for the women who developed GH (n = 113) vs. 775 women who remained normotensive, as well as for those who developed PE (n = 24) vs. 775 controls. The probability of each disease was assessed for the base prediction model (age + primiparity) and for the model extended by one (test) variable, using logistic regression. Three measures were used to assess the prediction: area under curve (AUC) of the base and extended model, integrated discrimination improvement (IDI) (the index shows the difference between the value of the mean change in the predicted probability between the group of sick and healthy women when a new factor is added to the model), and net reclassification improvement (NRI) (the index focuses on the reclassification table describing the number of women in whom an upward or downward shift in the disease probability value occurred after a new factor had been added, including results for healthy and sick women). In the GH prediction, AUC increased most strongly when we added BMI (kg/m2) as a continuous variable (AUC = 0.716, p < 0.001) to the base model. The highest IDI index was obtained for prior GH/PE (IDI = 0.068, p < 0.001). The addition of BMI as a continuous variable or BMI ≥ 25 kg/m2 improved the classification for healthy and sick women the most (NRI = 0.571, p < 0.001). In the PE prediction, AUC increased most strongly when we added BMI categories (AUC = 0.726, p < 0.001) to the base model. The highest IDI index was obtained for prior GH/PE (IDI = 0.050, p = 0.080). The addition of BMI categories improved the classification for healthy and sick women the most (NRI = 0.688; p = 0.001). After summing up the results of three indexes, the probability of hypertension in pregnancy was most strongly improved by BMI, including BMI ≥ 25 kg/m2 for the GH prediction, and BMI ≥ 30 kg/m2 for the PE prediction. Main conclusions: Pre-pregnancy BMI was the most likely factor to increase the probability of developing hypertension in pregnancy, compared to other risk factors. Hierarchies of PE and GH risk factors may suggest different (or common) mechanisms of their development.
Highlights
The severity of the obesity epidemic in the world is one of the reasons why we focused our attention on the assessment of the role of maternal obesity in the development of pregnancy [1,2]
We examined a number of clinical factors identified in the literature as potential risk factors for pregnancy-induced hypertension in order to compare them with the results obtained for the pre-pregnancy body mass index (BMI) [13]
The pre-pregnancy BMI was a strong factor in predicting both forms of pregnancy-induced hypertension, i.e., isolated gestational hypertension (GH) and preeclampsia (PE)
Summary
The severity of the obesity epidemic in the world is one of the reasons why we focused our attention on the assessment of the role of maternal obesity in the development of pregnancy [1,2]. Many studies have confirmed that pre-pregnancy obesity is an important part of the Development of Health and Disease (DOHaD) concept, in which factors influencing the intrauterine environment are risk factors for non-communicable diseases in adulthood. Pre-pregnancy obesity has been recognized as a strong risk factor for pregnancy-induced hypertension, independent of the influence of other confounders [7,8,9,10,11,12], but this does not prejudge us against the importance of obesity compared to other maternal risk factors [7]. Hypertension in pregnancy, especially preeclampsia (PE), is one of the main causes of mortality and morbidity in mothers and their babies, and the effects of the disease are limited to the perinatal period, and have long-term effects related to, e.g., a future higher risk of cardiovascular disease in both mothers and babies [13,15,16,17,18,19]
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