Evaluating the effect of maternal health conditions on severe maternal morbidity adjusting for emergent cesarean delivery: A mediation analysis approach

Abstract

The prevalence of pre-existing and gestational maternal health conditions is rising; affected women are at increased risk for both cesarean delivery (CD) and severe maternal morbidity (SMM). We estimated the increased risk of SMM associated with key maternal health conditions, and determined the extent to which it was directly associated with these conditions versus indirectly associated because of an increased risk of CD. Nulliparous, term, singleton, vertex (NTSV) gestations were identified among laboring women in California 2008-2010 hospital discharge datasets. Logistic regression models (stratified by younger vs. older women [≥ 35 years]) were constructed for each condition: chronic/gestational diabetes mellitus (DM), chronic/gestational hypertension, obesity, heart disease, and mental health diagnoses. Using mediation analysis, the potential effect associated with each condition (exposure) on SMM (outcome) consisted of a direct effect and an indirect effect caused by modification of the risk of an emergent CD (mediator). Of 502,654 deliveries, 24.3% had an emergent CD; 1.7% had SMM, which was present in 1.6% of younger vs. 2.2% of older mothers. The modeled odds ratios (ORs) for the direct effect on SMM were 2.00-2.67 for any hypertension, 0.78 for obesity in younger women, 6.57-7.97 for heart disease, and 1.43-1.58 for mental health diagnoses. No direct effect was identified for DM or obesity in older women. The ORs for the indirect effect were low, ranging from 0.94-1.11 for all models. For women laboring with NTSV gestations where key maternal health conditions were present, the risk of SMM mediated by an emergent CD was low, relative to the direct risk.

Indexing adult obesity by waist-to-height and weight-to-height ratios

“…By the age of 20 years adolescents become fully formed adults. [2] Pregnancies are not recommended 35 years of age or older; [19] persons with vulnerable backgrounds 35 years of age or older are recommended to undergo a screening for diabetes. [12] The age of 50 years is an approximate age of menopause.…”

“…To size this up, an estimated quarter of births in California, US have to be delivered via the caesarean section. [19] This may be related to obesity, miscalculated or imbalanced diet, albeit at the time of pregnancy. The obesity at the time of pregnancy can lead to macrosomia; particularly, women who had the gestational diabetes mellitus (GDM) may be affected.…”

“…They complicate about 40% of pregnancies with normal delivery and aggravate 50% of pregnancies with delivery via the caesarean section among women younger than 35 years, with rates for older women even higher: 50% and 60%, respectively. [19] Obviously, consecutive pregnancies provoke the risk in general. It has been also reported that women who experienced GDM are predisposed to the non-alcoholic fatty liver disease some years after their pregnancy.…”

The effect of maternal health conditions on maternal morbidity in women with a prior cesarean: the role of elective repeat cesarean delivery

“…In a previous study using a study population of nulliparous women who labored with term, singleton, vertex (NTSV) gestations and who delivered in California between 2008-2010, [37] we found that the modeled ORs for the direct effect of emergent CD on SMM were 2.0-2.7 for hypertension, 6.6-7.7 for heart disease, and 1.4-1.6 for mental health diagnoses. In this previous work, we did not identify a direct effect for diabetes mellitus or obesity.…”

“…[36] Instead, analyses should recognize that these conditions have both direct and indirect effects, with the indirect effect of the conditions being mediated through an elective CD. In a previous study [37] we examined the mediating effect of primary CD in nulliparous, term, singleton, vertex (NTSV) laboring deliveries on the association between SMM and pre-existing and gestational conditions. We used mediation analysis to decompose the risk associated with a condition or exposure into the direct effect (DE) of the condition and the indirect effect (IE) of the condition, where the total effect (TE) equals DE*IE.…”