Graduation Year

2017

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Public Health

Major Professor

Kathleen O’Rourke, Ph.D., M.P.H.

Co-Major Professor

William Sappenfield, M.D., M.P.H.

Committee Member

William Callaghan, M.D., M.P.H.

Committee Member

Alfred Mbah, Ph.D., M.S.

Committee Member

Roneé Wilson, Ph.D., M.P.H.

Keywords

Pregnancy Complications, Near miss, BMI, Obstetrics

Abstract

Severe maternal morbidity generally refers to the most severe complications of pregnancy and includes: hemorrhage, embolism, acute renal failure, stroke, acute myocardial infarction, and other complications. These complications affect more than 50,000 women in the United States every year, with rates significantly increasing from 1998 to 2011. In an effort to reduce these increasing complication rates, clinicians and researchers have emphasized the need to identify potential modifiable risk factors for severe maternal morbidity, and the need to study the relationships between these risk factors and severe maternal morbidity. The overall goal of this study is to improve the understanding of the increasing rates of severe maternal morbidity.

The objective of the first study is to examine the association between prepregnancy BMI and severe maternal morbidity in women residing in Florida who had a live birth during 2007-2014. Additionally, the specific association between prepregnancy BMI and the most common individual conditions that comprise the composite measure of severe maternal morbidity will also be examined. We conducted a population-based retrospective cohort study using Florida’s linked birth certificate and maternal hospital discharge data for the years 2007-2014. The risk of severe maternal morbidity associated with BMI was then estimated by odds ratios (OR) and 95% confidence intervals (CI) derived using generalized estimating equations (GEE) for logistic regression. This final model was rerun separately for the most common conditions that comprise severe maternal morbidity as the outcome measure to assess differences by type of condition. Unadjusted rates of severe maternal morbidity increased with increasing BMI; however, after risk adjustment overweight and obese women had slightly protective odds of severe maternal morbidity when compared with normal weight women. The association between prepregnancy BMI and severe maternal morbidity differs by types of severe maternal morbidity. A protective dose-response relationship was seen for blood transfusion and disseminated intravascular coagulation, with the odds of morbidity decreasing with increasing BMI. The odds of heart failure, adult respiratory distress syndrome, and ventilation all increased with increasing BMI. This study shows that severe maternal morbidity is a complex measure and not just a single condition. In future studies, it will be imperative to analyze severe maternal morbidity as a composite measure and as individual conditions to identify modifiable risk factors to focus on for interventions.

The objective of the second study is to identify potential determinants of the increase in the rate of severe maternal morbidity among women residing in Florida who had a live birth during 2005-2014. We examined severe maternal morbidity rates and related risk factors in live births to Florida women between 2005 and 2014, using Florida’s linked birth certificate and hospital discharge data. We initially conducted a Kitagawa analysis to evaluate the components of the increased rate of severe maternal morbidity between 2005 and 2014. Additionally, we performed a multivariable regression analysis to estimate the contribution of the multiple factors to differences in the rate of severe maternal morbidity in 2005 and 2014. The rate of severe maternal morbidity in 2014 was 19.3 per 1,000 live births, which was 1.65 times higher than the rate in 2005. Nearly all of the excess severe maternal morbidity and blood transfusions in 2014 can be explained by differences in the rate of severe maternal morbidity and blood transfusion between the two time periods. In total, sociodemographic factors, medical factors, and individual and hospital health service factors explained 9.1% of the overall severe maternal morbidity increase in 2014 compared with 2005, and only explained 2.5% of the increase in blood transfusions during this time period. Our study findings indicate that the increase in the rate of severe maternal morbidity is comprised almost entirely by an increase in the rate of blood transfusions. Further research will need to be conducted to explain the increase in the rate of severe maternal morbidity and blood transfusions.

Consistent with national trends, the rates of severe maternal morbidity have been increasing in Florida. This increase is driven almost entirely by blood transfusions and cannot be explained by traditional factors that are readily available in current datasets. In addition to the differences between the trends of blood transfusions and the 20 severe maternal morbidity conditions, there are also differences in risk factors associated with these different conditions. Prepregnancy overweight and obesity is associated with a protective effect with blood transfusions and disseminated intravascular coagulation that is not seen in the other conditions. Therefore, initiatives to decrease the rates of severe maternal morbidity will need to take these differences into account.

Available for download on Wednesday, May 09, 2018

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