Syringeal vocal folds do not have a voice in zebra finch vocal development.

Vocal behavior can be dramatically changed by both neural circuit development and postnatal maturation of the body. During song learning in songbirds, both the song system and syringeal muscles are functionally changing, but it is unknown if maturation of sound generators within the syrinx contributes to vocal development. Here we densely sample the respiratory pressure control space of the zebra finch syrinx in vitro. We show that the syrinx produces sound very efficiently and that key acoustic parameters, minimal fundamental frequency, entropy and source level, do not change over development in both sexes. Thus, our data suggest that the observed acoustic changes in vocal development must be attributed to changes in the motor control pathway, from song system circuitry to muscle force, and not by material property changes in the avian analog of the vocal folds. We propose that in songbirds, muscle use and training driven by the sexually dimorphic song system are the crucial drivers that lead to sexual dimorphism of the syringeal skeleton and musculature. The size and properties of the instrument are thus not changing, while its player is.

Mode of Delivery and Asthma at School Age in 9 European Birth Cohorts.

Evidence on the association between mode of delivery and asthma at school age is inconclusive. We assessed the associations between specific modes of delivery and asthma in children from 9 European birth cohorts that enrolled participants between 1996 and 2006. Cohort-specific crude and adjusted risk ratios for asthma at ages 5-9 years were calculated using Poisson regression models and pooled. A sensitivity analysis was carried out in children born at term to reduce confounding due to perinatal factors. The study included 67,613 participants. Cohort-specific rates of cesarean delivery varied from 9.4% to 37.5%. Cesarean delivery, as opposed to vaginal delivery, was associated with an increased risk of asthma (adjusted risk ratio (aRR) = 1.22, 95% confidence interval (CI): 1.02, 1.46). Compared with spontaneous vaginal delivery, the adjusted risk ratio was 1.33 (95% CI: 1.02, 1.75) for elective cesarean delivery, 1.07 (95% CI: 0.94, 1.22) for emergency cesarean delivery, and 0.97 (95% CI: 0.84, 1.12) for operative vaginal delivery. In children born at term, the associations were strengthened only for elective cesarean delivery (aRR = 1.49, 95% CI: 1.13, 1.97). The large sample size allowed analysis of the associations between specific modes of delivery and asthma at school age. The increased risk of asthma associated with elective cesarean delivery, especially among children born at term, is relevant in counteracting the increasing use of this procedure, which is often performed without a clear medical indication.

Maternal complications in pregnancy and wheezing in early childhood: a pooled analysis of 14 birth cohorts.

BACKGROUND: Evidence on the effect of maternal complications in pregnancy on wheezing in offspring is still insufficient. METHODS: A pooled analysis was performed on individual participant data from fourteen European birth cohorts to assess the relationship between several maternal pregnancy complications and wheezing symptoms in the offspring. Exposures of interest included hypertension and preeclampsia, diabetes, as well as pre-pregnancy overweight (body mass index between 25 and 29.9) and obesity (body mass index ≥ 30) compared with normal weight (body mass index between 18.5 and 24.9). Outcomes included both ever and recurrent wheezing from birth up to 12-24 months of age. Cohort-specific crude and adjusted risk ratios (RR) were calculated using log-binomial regression models and then pooled using a random effects model. RESULTS: The study included 85509 subjects. Cohort-specific prevalence of ever wheezing varied from 20.0% to 47.3%, and of recurrent wheezing from 3.0% to 14.3%. Adjusted pooled RR for ever and recurrent wheezing were: 1.02 (95% CI: 0.98-1.06) and 1.20 (95% CI: 0.98-1.47) for hypertensive disorders; 1.09 (95% CI: 1.01-1.18) and 1.23 (95% CI: 1.07-1.43) for preeclampsia; 1.04 (95% CI: 0.97-1.13) and 1.24 (95% CI: 0.86-1.79) for diabetes; 1.08 (95% CI: 1.05-1.11) and 1.19 (95% CI: 1.12-1.26) for overweight; 1.12 (95% CI: 1.08-1.17) and 1.16 (95% CI: 0.97-1.39) for obesity. No heterogeneity was found in RR estimates among the cohorts, except for diabetes and recurrent wheezing (P=0.027). CONCLUSIONS: Preeclampsia, maternal pre-pregnancy overweight and obesity are associated with an increase risk of wheezing in the offspring.

Preterm birth, infant weight gain, and childhood asthma risk: a meta-analysis of 147,000 European children.

BACKGROUND: Preterm birth, low birth weight, and infant catch-up growth seem associated with an increased risk of respiratory diseases in later life, but individual studies showed conflicting results. OBJECTIVES: We performed an individual participant data meta-analysis for 147,252 children of 31 birth cohort studies to determine the associations of birth and infant growth characteristics with the risks of preschool wheezing (1-4 years) and school-age asthma (5-10 years). METHODS: First, we performed an adjusted 1-stage random-effect meta-analysis to assess the combined associations of gestational age, birth weight, and infant weight gain with childhood asthma. Second, we performed an adjusted 2-stage random-effect meta-analysis to assess the associations of preterm birth (gestational age <37 weeks) and low birth weight (<2500 g) with childhood asthma outcomes. RESULTS: Younger gestational age at birth and higher infant weight gain were independently associated with higher risks of preschool wheezing and school-age asthma (P < .05). The inverse associations of birth weight with childhood asthma were explained by gestational age at birth. Compared with term-born children with normal infant weight gain, we observed the highest risks of school-age asthma in children born preterm with high infant weight gain (odds ratio [OR], 4.47; 95% CI, 2.58-7.76). Preterm birth was positively associated with an increased risk of preschool wheezing (pooled odds ratio [pOR], 1.34; 95% CI, 1.25-1.43) and school-age asthma (pOR, 1.40; 95% CI, 1.18-1.67) independent of birth weight. Weaker effect estimates were observed for the associations of low birth weight adjusted for gestational age at birth with preschool wheezing (pOR, 1.10; 95% CI, 1.00-1.21) and school-age asthma (pOR, 1.13; 95% CI, 1.01-1.27). CONCLUSION: Younger gestational age at birth and higher infant weight gain were associated with childhood asthma outcomes. The associations of lower birth weight with childhood asthma were largely explained by gestational age at birth.