Preeclampsia: a renal perspective

Preeclampsia is a syndrome that affects 5% of all pregnancies, producing substantial maternal and perinatal morbidity and mortality. The aim of this review is to summarize our current understanding of the pathogenesis of preeclampsia with special emphasis on the recent discovery that circulating anti-angiogenic proteins of placental origin may play an important role in the pathogenesis of proteinuria and hypertension of preeclampsia.     

Divergent trends in maternal cigarette smoking during pregnancy: United States 1990-99

While examination of causes for trends in smoking have largely focused on how changes have occurred with maternal age and, less commonly, time period, little is known as to how age, period and birth cohort interact on trends in the prevalence of smoking during pregnancy. We performed a population-based, retrospective cohort study based on the vital statistics records comprised of White (n=24,499,629) and Black (n = 5,096,625) women delivering in the United States in 1990-99. Smoking prevalence rates were derived by seven 5-year maternal age groups (15-19 to 45-49 years), two time periods (1990-94 and 1995-99), and eight 5-year maternal birth cohorts (1945-49 to 1980-84) after adjusting for the confounding effects of gravidity, education, marital status, and lack of prenatal care through multivariable logistic regression models. The prevalence of smoking was 17.3% among Whites, and 13.5% among Blacks, with substantial variations by age, time period, and birth cohort. The rate declined with increasing age among Whites during the 1990-94 and 1995-99 periods. Among Blacks, the rates increased steeply with advancing age up to 25-29 years and began to decline thereafter. Smoking rates declined among both Whites and Blacks with increasing birth cohort within each age strata. These rates were highest among multigravid women (gravida > or = 2), and lowest among primigravid women. The rates among Whites declined with increasing maternal age for each gravida. Among Blacks, smoking rates for each gravida increased with advancing age up to 25-29 years, and plateaued among older women. Variation in smoking prevalence by age, time period, and birth cohort provides impetus for designing interventions to reduce smoking. Such studies should not only consider cross-sectional trends, but also the divergent patterns by age and cohort among women of different race/ethnic groups and gravidity.     

A parsimonious explanation for intersecting perinatal mortality curves: understanding the effects of race and of maternal smoking

Background  

Neonatal mortality rates among black infants are lower than neonatal mortality rates among white infants at birth weights <3000 g, whereas white infants have a survival advantage at higher birth weights. This finding is also observed when birth weight-specific neonatal mortality rates are compared between infants of smokers and non-smokers. We provide a parsimonious explanation for this paradoxical phenomenon.     

Reexamining the effects of gestational age, fetal growth, and maternal smoking on neonatal mortality

BACKGROUND: Low birth weight (<2,500 g) is a strong predictor of infant mortality. Yet low birth weight, in isolation, is uninformative since it is comprised of two intertwined components: preterm delivery and reduced fetal growth. Through nonparametric logistic regression models, we examine the effects of gestational age, fetal growth, and maternal smoking on neonatal mortality. METHODS: We derived data on over 10 million singleton live births delivered at >/= 24 weeks from the 1998-2000 U.S. natality data files. Nonparametric multivariable logistic regression based on generalized additive models was used to examine neonatal mortality (deaths within the first 28 days) in relation to fetal growth (gestational age-specific standardized birth weight), gestational age, and number of cigarettes smoked per day. All analyses were further adjusted for the confounding effects due to maternal age and gravidity. RESULTS: The relationship between standardized birth weight and neonatal mortality is nonlinear; mortality is high at low z-score birth weights, drops precipitously with increasing z-score birth weight, and begins to flatten for heavier infants. Gestational age is also strongly associated with mortality, with patterns similar to those of z-score birth weight. Although the direct effect of smoking on neonatal mortality is weak, its effects (on mortality) appear to be largely mediated through reduced fetal growth and, to a lesser extent, through shortened gestation. In fact, the association between smoking and reduced fetal growth gets stronger as pregnancies approach term. CONCLUSIONS: Our study provides important insights regarding the combined effects of fetal growth, gestational age, and smoking on neonatal mortality. The findings suggest that the effect of maternal smoking on neonatal mortality is largely mediated through reduced fetal growth.     

Trends in twin neonatal mortality rates in the United States, 1989 through 1999: influence of birth registration and obstetric intervention

OBJECTIVE: We sought to evaluate the contributions of changes in birth registration, labor induction, and cesarean delivery on trends in twin neonatal mortality rates. STUDY DESIGN: We conducted a population-based, retrospective cohort study of twin live births, using linked birth-infant death data in the United States (1989-1999). Relative risks and 95% confidence intervals that quantified changes in neonatal (0-27 days) mortality rates were derived from ecologic logistic regression models that were fit after aggregation of the data by each state in the United States. RESULTS: The frequency of live born twins who weighed <500 g increased 72%, from 0.7% in 1989 to 1.2% in 1999, of live born twins who weighed 500 to 749 g and 750 to 999 g increased by 55% and 28%, respectively, between 1989 and 1999. Preterm birth rates increased by 19%, from 46.2% in 1989 to 57.2% in 1999. The rate of labor induction increased from 5.8% to 13.9%, and the cesarean delivery rate increased from 49.8% to 56.3%. Between 1989 to 1991 and 1997 to 1999, the crude neonatal mortality rates among twins who weighed >or=500 g declined by 37% (95% CI, 35%-40%) from 21.5 to 13.6 per 1000 twin live births. Adjustments for preterm labor induction, preterm cesarean delivery, term labor induction, term cesarean delivery, and sociodemographic factors had little influence on neonatal mortality rate trends. CONCLUSION: Increases in preterm birth because of obstetric intervention among twins have not led to increases in twin neonatal mortality rates in the United States.     

Estimation of cumulative odds ratios

PURPOSE: Standard estimation of ordered odds ratios requires the constraint that the etiologic effects of exposure are homogenous across thresholds of the ordered response. We present a method to relax this often-unrealistic constraint. METHODS: The kernel of the proposed method is the expansion of observed data into "person-thresholds." Using standard statistical software, for each subject we create a separate record for each response threshold and then apply binary logistic regression to estimate generalized cumulative odds ratios for one or more exposures. RESULTS: Two examples demonstrate that the proposed method provides increased flexibility in assessing the etiologic effects of exposures. A Monte Carlo simulation study supports the proposed approach by suggesting the estimated cumulative odds ratios are unbiased with proper confidence interval coverage attained by use of generalized estimating equations. CONCLUSION: The proposed method provides simple estimates of ordered odds ratios that allow the etiologic effects of exposure to vary across levels of the ordered response.     

Risk factors for elevated intraocular pressure in uveitis

PURPOSE: To determine the prevalence of raised intraocular pressure (IOP) in patients with uveitis and to identify risk factors for raised IOP in patients with uveitis. PATIENTS AND METHODS: Consecutive case notes of 257 patients (402 eyes) attending a specialist uveitis clinic during a three-month period were reviewed. Patients with raised IOP were identified and further evaluated. Risk factors for raised IOP were determined. RESULTS: The prevalence of raised IOP in the study eyes was 41.8%. The prevalence of raised IOP requiring treatment was 29.8%. Raised IOP was found in 26.0% of eyes with acute uveitis and 46.1% of eyes with chronic uveitis. This difference was significant (P = 0.002). Similarly the prevalence of raised IOP requiring treatment in acute and chronic uveitis was 15.1% and 33.8%, respectively. This difference was also significant (P = 0.002). Active inflammation was significantly associated with raised IOP (P = 0.031). Steroid usage, increasing age, and number of years since diagnosis were significantly correlated with raised IOP (P = 0.008, P = 0.022, and P = 0.006, respectively); 9.6% of the study eyes developed glaucoma. The majority of these eyes (69.7%) were treated medically. The remainder (30.3%) required both medical and surgical management. CONCLUSION: Raised IOP is significantly more common in patients with chronic intraocular inflammation than those with acute uveitis. Risk factors for elevated IOP that should enable closer monitoring of 'at-risk' eyes have been identified.