Hormonal evidence supports the theory of selection in utero.

OBJECTIVES: Antagonists in the debate over whether the maternal stress response during pregnancy damages or culls fetuses have invoked the theory of selection in utero to support opposing positions. We describe how these opposing arguments arise from the same theory and offer a novel test to discriminate between them. Our test, rooted in reports from population endocrinology that human chorionic gonadotropin (hCG) signals fetal fitness, contributes not only to the debate over the fetal origins of illness, but also to the more basic literature concerned with whether and how natural selection in utero affects contemporary human populations. METHODS: We linked maternal serum hCG measurements from prenatal screening tests with data from the California Department of Public Health birth registry for the years 2001-2007. We used time series analysis to test the association between the number of live-born male singletons and median hCG concentration among males in monthly gestational cohorts. RESULTS: Among the 1.56 million gestations in our analysis, we find that median hCG levels among male survivors of monthly conception cohorts rise as the number of male survivors falls. RESULTS: Elevated median hCG among relatively small male birth cohorts supports the theory of selection in utero and suggests that the maternal stress response culls cohorts in gestation by raising the fitness criterion for survival to birth.

Perinatal morbidity associated with late preterm deliveries compared with deliveries between 37 and 40 weeks of gestation.

OBJECTIVE: To estimate the risk of short-term complications in neonates born between 34 and 36 weeks of gestation. DESIGN: This is a retrospective cohort study. SETTING: Deliveries in 2005 in the USA. POPULATION: Singleton live births between 34 and 40 weeks of gestation. METHODS: Gestational age was subgrouped into 34, 35, 36 and 37-40 completed weeks of gestation. Statistical comparisons were performed using chi-square test and multivariable logistic regression models, with 37-40 weeks of gestation designated as referent. MAIN OUTCOME MEASURES: Perinatal morbidities, including 5-minute Apgar scores, hyaline membrane disease, neonatal sepsis/antibiotics use, and admission to the intensive care unit. RESULTS: In all, 175,112 neonates were born between 34 and 36 weeks in 2005. Compared with neonates born between 37 and 40 weeks, neonates born at 34 weeks had higher odds of 5-minute Apgar <7 (adjusted odds ratio [aOR] 5.51, 95% CI 5.16-5.88), hyaline membrane disease (aOR 10.2, 95% CI 9.44-10.9), mechanical ventilation use >6 hours (aOR 9.78, 95% CI 8.99-10.6) and antibiotic use (aOR 9.00, 95% CI 8.43-9.60). Neonates born at 35 weeks were similarly at risk of morbidity, with higher odds of 5-minute Apgar <7 (aOR 3.42, 95% CI 3.23-3.63), surfactant use (aOR 3.74, 95% CI 3.21-4.22), ventilation use >6 hours (aOR 5.53, 95% CI 5.11-5.99) and neonatal intensive-care unit admission (aOR 11.3, 95% CI 11.0-11.7). Neonates born at 36 weeks remain at higher risk of morbidity compared with deliveries at 37-40 weeks of gestation. CONCLUSIONS: Although the risk of undesirable neonatal outcomes decreases with increasing gestational age, the risk of neonatal complications in late preterm births remains higher compared with infants delivered at 37-40 weeks of gestation.

Neonatal mortality among low birth weight infants during the initial months of the academic year.

OBJECTIVE: Proper management of very low weight (<1500 g) infants requires specific expertise. During July and August, pediatric interns start new rotations and advance in responsibilities by postgraduate level. We test the hypothesis that low weight births in teaching hospitals exhibit increased neonatal mortality during the initial training months. STUDY DESIGN: Population-based cohort of 5184 very low weight and 15 232 moderately low weight infants in California from 19 regional teaching hospitals with medical training programs. Logistic regression methods controlled for both individual covariates and temporal patterns in neonatal mortality. RESULT: We found no difference in neonatal mortality between very low weight infants born in teaching hospitals during July and August and those born in other months (adjusted odds ratio (AOR): 0.98, 95% confidence interval (CI), 0.78 to 1.23). Investigation of moderately low birth weight infants also indicated no increased neonatal mortality. CONCLUSION: Infants most likely to die in the neonatal period do not appear to be at elevated risk of neonatal mortality during July and August.

Does the employed technique of endotracheal extubation reduce the risk of aspiration?

Aspiration of gastric contents continues to be one of the most serious complications of general anesthesia. Laryngeal competence may be reduced immediately following endotracheal extubation, which may increase the risk of aspiration. An evaluation research design was used in 20 adult canines to compare the techniques of positive pressure extubation and extubation at the height of inspiration employing radiopaque barium. Evaluation of radiographs from both groups revealed that no aspirate of barium was detected in the tracheobronchial trees of any of the dogs. This study establishes that there is no difference in the risk of aspiration following endotracheal extubation using the canine model regardless of the clinical technique employed.