Obesity in obstetric care : Consequences and risk prediction

Abstract: The incidence of obesity is increasing at an alarming rate worldwide and the epidemic has reached the pregnant population of developed countries. Obesity is associated with several obstetric complications for both the mother, the fetus and the new-born. Today, obesity risk assessment is based on body mass index (BMI). However, the majority of women considered obese based on BMI will have an event-free pregnancy and delivery. Obesity is one of the greatest challenges for obstetricians and improving prediction of risk among obese women is essential.The overall aim of this thesis was to increase the capacity for early pregnancy prediction of obesity-related late adverse pregnancy outcomes in women with overweight and obesity. The thesis encompassed four population-based cohort studies. The first showed that obesity in early pregnancy modulated the association between depression and infant birthweight. Women with obesity and depression gave birth to infants with higher birthweight than non-depressive obese women. The opposite pattern was seen in normal-weight women, where depressed women gave birth to infants with lower birthweight than non-depressive women. About one-third of pregnant women with obesity are metabolically unhealthy, which was the focus of the second study. Almost half of those women developed at least one obesity-related complication and the risk was higher than in women with obesity who were metabolically healthy. The difference seemed to have little clinical relevance. Further, women with metabolically unhealthy obesity have numerous risk factors for development of cardiovascular disease later in life, including altered levels of cardiovascular markers in blood samples. The third and fourth studies explored if estimation of fat distribution in the first half of pregnancy predicted preeclampsia development. It was found that waist circumference (WC) measured in the first trimester was associated with increased risk of developing preeclampsia. However, first-trimester WC was highly correlated with BMI and adding WC to a prediction model already including BMI did not improve its prediction performance. The research team also measured abdominal adipose tissue with ultrasound in the second trimester. Both subcutaneous adipose tissue (SAT) thickness and visceral adipose tissue (VAT) thickness were associated with preeclampsia development, but only SAT thickness had an association that remained after adjustment for BMI.In conclusion, assessment of obese women in early pregnancy for detection of high risk for obesity-related complications is essential. Comorbidity of other diseases, such as depression, should be taken into account. Metabolically unhealthy obesity during pregnancy has little impact in the short term, but might be an opportunity for prevention of long-term consequences in obese women. Central obesity, measured as WC or SAT/VAT thickness, was associated with preeclampsia, but only SAT thickness seemed to improve prediction of preeclampsia in models already addressing obesity as BMI.