Severe maternal morbidity associated with endometriosis: a population-based, retrospective cohort study.

OBJECTIVE: To evaluate the association between endometriosis and the risk of severe maternal morbidity (SMM) as defined by the Centers for Disease Control and Prevention. DESIGN: This was a population-based, retrospective cohort study using the California Office of Statewide Health Planning and Development Linked Birth File with hospital discharge International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) diagnoses between 2007 and 2012. SETTING: Population-based. PATIENT(S): A total of 3,098,578 pregnancies from 2007 to 2012. INTERVENTION(S): Prior diagnosis of endometriosis identified using the ICD-9-CM codes 617.0-617.9. MAIN OUTCOME MEASURE(S): The primary outcome of interest was SMM, which was defined as having been diagnosed with any of the ICD-9-CM codes corresponding to 25 peripartum conditions listed by the Centers for Disease Control and Prevention. The secondary outcomes of interest were each individual condition. RESULT(S): Of the 3,098,578 pregnancies analyzed, 2,910 pregnancies were among women with a prior diagnosis of endometriosis. There were 45,655 pregnancies complicated by at least 1 SMM; 158 pregnancies (54.3 per 1,000 pregnancies) were in women with endometriosis and 45,497 (14.7 per 1,000 pregnancies) were in women without endometriosis. Women with pregnancies complicated by endometriosis were 2.41 times more likely to develop SMM than women who did not have endometriosis (adjusted odds ratio [aOR], 2.41; 95% confidence interval [CI], 2.03-2.87). There was an increased risk of disseminated intravascular coagulation (aOR, 2.46; 95% CI, 1.65-3.66), heart failure during a procedure or surgery (aOR, 2.58; 95% CI, 1.69-3.94), pulmonary edema (aOR, 3.02; 95% CI, 1.11-8.17), blood transfusion (aOR, 2.17; 95% CI, 1.75-2.68), and hysterectomy (aOR, 2.46; 95% CI, 1.58-3.85). When the association was stratified by delivery mode, the risk of SMM was higher for vaginal delivery (aOR, 4.59; 95% CI, 2.73-7.71) than for cesarean delivery (aOR, 1.64; 95% CI, 1.37-1.97) (P-interaction<.0001). CONCLUSION(S): This study demonstrated that endometriosis is a major risk factor for SMM, especially among those who deliver vaginally. Furthermore, precautions should be taken before delivery in anticipation of potential complications.

Use of meconium in perinatal epidemiology: potential benefits and pitfalls.

PURPOSE: Meconium is a biomarker matrix that can be used to assess cumulative exposures in epidemiologic studies of prenatal risk factors. Depending on when meconium is collected, different exposure windows during pregnancy can be measured. However, little guidance exists regarding the extent to which timing of meconium collection will influence resulting effect estimates. METHODS: We performed a simulation study of prenatal tobacco smoke exposure (assessed from meconium nicotine) and birth weight. We discuss four typical meconium collection methods capturing different exposure windows and assess the biases induced by these methods. RESULTS: In simulations assuming that exposure to tobacco smoke only during late gestation was of etiologic relevance to birth weight, use of a meconium collection method that captured exposure windows other than late gestation resulted in biased estimates of the true nicotine-birth weight association. CONCLUSIONS: Using meconium collection methods that do not reflect an exposure window of etiologic relevance can lead to biased results and erroneous conclusions regarding the nature of prenatal exposure-outcome associations. Understanding how prenatal exposure patterns vary across the pregnancy and exposure windows of etiologic relevance is essential in determining when and how to collect meconium for use in biomarker studies of prenatal exposure.