Individual accumulation of heterogeneous risks explains perinatal inequalities within deprived neighbourhoods

Effectiveness of score card-based antenatal risk selection, care pathways, and multidisciplinary consultation in the Healthy Pregnancy 4 All study (HP4ALL): study protocol for a cluster randomized controlled trial

BACKGROUND

Promotion of healthy pregnancies has gained high priority in the Netherlands because of relatively unfavorable perinatal outcomes. In response, a nationwide study, 'Healthy Pregnancy 4 All' (HP4ALL), has been initiated. Part of this study involves systematic and broadened antenatal risk assessment (the Risk Assessment substudy). Risk selection in current clinical practice is mainly based on medical risk factors. Despite the increasing evidence for the influence of nonmedical risk factors (social status, lifestyle or ethnicity) on perinatal outcomes, these risk factors remain highly unexposed. Systematic risk selection, combined with customized care pathways to reduce or treat detected risks, and regular and structured consultation between community midwives, gynecologists and other care providers such as social workers, is part of this study.

METHODS/DESIGN

Neighborhoods in 14 municipalities with adverse perinatal outcomes above national and municipal averages are selected for participation. The study concerns a cluster randomized controlled trial. Municipalities are randomly allocated to intervention (n = 3,500 pregnant women) and control groups (n = 3,500 pregnant women). The intervention consists of systematic risk selection with the Rotterdam Reproductive Risk Reduction (R4U) score card in pregnant women at the booking visit, and referral to corresponding care pathways. A risk score, based on weighed risk factors derived from the R4U, above a predefined threshold determines structured multidisciplinary consultation. Primary outcomes of this trial are dysmaturity (birth weight < p10), prematurity (birth <37 weeks), and efficacy of implementation.

DISCUSSION

The 'HP4ALL' study introduces a systematic approach in antenatal health care that may improve perinatal outcomes and, thereby, affect future health status of a new generation in the Netherlands.

TRIAL REGISTRATION

Dutch Trial Registry ( NTR-3367) on 20 March 2012.

Worries surrounding the first ultrasound do not bias the screening for depressive and anxiety symptoms during pregnancy

INTRODUCTION

Antenatal screening for depressive/anxiety symptoms could be biased by worries surrounding the first ultrasound (US). Therefore, we examined the potential influence of worries surrounding the first US on systematic screening for depressive/anxiety symptoms during pregnancy.

MATERIALS AND METHODS

We obtained data from 573 women screened consecutively in midwifery practices and hospitals in the Netherlands. Data included the Edinburgh Depression Scale (EDS), having had an US, and its perceived influence on women's worries.

RESULTS

In total, 18% had EDS scores ≥10 (n = 105). Among 392 women who underwent an US, currently existing worries, introduced or unaltered by the US, predicted depressive/anxiety symptoms (aOR: 3.41, P < 0.001). Among 181 women who did not undergo an US, expected continuation of existing worries after the US predicted depressive/anxiety symptoms (aOR: 18.84, P = 0.046), in contrast to worries which were expected to subside.

DISCUSSION

In our cohort, depressive and/or anxiety symptoms were not associated with transient worries, reduced by a first US, suggesting no bias. If true, antenatal screening for anxiety/depressive symptoms should not depend on the timing of this US examination.

Unemployment at municipality level is associated with an increased risk of small for gestational age births--a multilevel analysis of all singleton births during 2005-2010 in Finland

Introduction

Neighbourhood level deprivation has been shown to influence adverse perinatal outcomes independent of individual level socioeconomic status (SES) in countries with high income inequality, such as the United States. The present study evaluates whether municipality level deprivation defined based on education (proportion of inhabitants with university level education), income (mean income per capita) and unemployment were associated with the prevalence of preterm birth (<37 weeks) and small for gestational age (SGA, birth weight <2 standard deviations) after adjustment for individual level socio-demographics (age, parity, prior preterm births, smoking during pregnancy and SES defined based on maternal occupation at birth) in Finland.

Methods

The study design was cross-sectional. The data gathered from the Medical Birth Register included all singleton births (n = 345,952) in 2005–2010. We fitted Generalized Estimating Equations (GEE) models to account for correlation of preterm birth and SGA clustering within municipality.

Results

Of all the women with singleton pregnancies, 4.5% (n = 15,615) gave birth preterm and 3.8% (n = 13,111) of their newborns were classified as SGA. Individual level SES and smoking were important risk factors for each outcome in adjusted models. Controlling for individual level factors, women living in intermediate and high unemployment class municipalities were 6.0% (adjusted odds ratio (aOR) = 1.06; 95% confidence interval (CI) 1.01-1.12) and 13.0% (aOR = 1.13; 95% CI 1.06-1.20), respectively, more likely to give birth to an SGA newborn than women living in low unemployment class municipalities.

Conclusions

After adjustment for individual level socio-demographics, the prevalence of SGA was around 6-13% higher in municipalities with an intermediate or high unemployment rate than municipalities with the lowest unemployment rate. The results suggested that the unemployment rate has an important public health effect with clinical implications since SGA is associated with a higher risk of adverse long-term health outcomes.

Bridging between professionals in perinatal care: towards shared care in the Netherlands

Relatively high perinatal mortality rates in the Netherlands have required a critical assessment of the national obstetric system. Policy evaluations emphasized the need for organizational improvement, in particular closer collaboration between community midwives and obstetric caregivers in hospitals. The leveled care system that is currently in place, in which professionals in midwifery and obstetrics work autonomously, does not fully meet the needs of pregnant women, especially women with an accumulation of non-medical risk factors. This article provides an overview of the advantages of greater interdisciplinary collaboration and the current policy developments in obstetric care in the Netherlands. In line with these developments we present a model for shared care embedded in local 'obstetric collaborations'. These collaborations are formed by obstetric caregivers of a single hospital and all surrounding community midwives. Through a broad literature search, practical elements from shared care approaches in other fields of medicine that would suit the Dutch obstetric system were selected. These elements, focusing on continuity of care, patient centeredness and interprofessional teamwork form a comprehensive model for a shared care approach. By means of this overview paper and the presented model, we add direction to the current policy debate on the development of obstetrics in the Netherlands. This model will be used as a starting point for the pilot-implementation of a shared care approach in the 'obstetric collaborations', using feedback from the field to further improve it.

Determinants of number-specific recall error of last menstrual period: a retrospective cohort study

OBJECTIVE

To assess the digit preference for last menstrual period (LMP) dates, associated determinants and impact on obstetric outcome.

DESIGN

Retrospective cohort study.

SETTING

University medical centre (the Netherlands).

POPULATION

Cohort of 24 665 LMP records and a subgroup of 4630 cases with known crown-rump length (CRL) measurement, and obstetric outcome.

METHODS

Digit preference was determined by comparing the observed to expected counts of each day. Associated determinants were identified by multivariate regression analysis. Differences in obstetric outcome between LMP and CRL dating were analysed.

MAIN OUTCOME MEASURES

(Non)deprived neighbourhood, cycle irregularity, certainty of LMP date, maternal age, smoking, body mass index, parity and ultrasound investigator. Preterm and post-term delivery.

RESULTS

LMP digit preference for the first [odds ratio (OR), 1.28; 95% confidence interval (95% CI), 1.20-1.36], fifth (OR, 1.10; 95% CI, 1.03-1.17), 10th (OR, 1.17; 95% CI, 1.09-1.25), 15th (OR, 1.31; 95% CI, 1.23-1.40), 20th (OR, 1.22; 95% CI, 1.15-1.30) and 25th (OR, 1.08; 95% CI, 1.01-1.15) days of the month occurred more often than expected. Digit preference occurred more frequently in women living in a deprived neighbourhood (OR, 1.21; 95% CI, 1.06-1.39), with uncertain LMP (OR, 2.03; 95% CI, 1.63-2.52) or irregular cycle (OR, 1.24; 95% CI, 1.06-1.44). More post-term (≥42 weeks) deliveries (OR, 1.27; 95% CI, 1.05-1.54) were observed in LMP dating. This effect was larger in women with a digit preference (OR, 1.56; 95% CI, 1.03-2.37).

CONCLUSIONS

LMP digit preference occurs more often in women living in deprived neighbourhoods, with uncertain LMP or an irregular cycle. LMP-dated pregnancies are associated with more post-term pregnancies.

Neighborhood socioeconomic disadvantage and gestational weight gain and loss

We explored the relationship between neighborhood socioeconomic disadvantage (NSED) and gestational weight gain and loss and if the association differed by race. A census tract level NSED index (categorized as low, mid-low, mid-high, and high) was generated from 12 measures from the 2000 US Census data. Gestational weight gain and other individual-level characteristics were derived from vital birth records for Allegheny County, PA for 2003-2010 (n = 55,608). Crude and adjusted relative risks were estimated using modified multilevel Poisson regression models to estimate the association between NSED and excessive and inadequate gestational weight gain (GWG) and weight loss (versus adequate GWG). Black women lived in neighborhoods that were more likely to be socioeconomically disadvantaged compared to white women. Almost 55% of women gained an excessive amount of weight during pregnancy, and 2% lost weight during pregnancy. Black women were more likely than white women to have inadequate weight gain or weight loss. Mid-high (aRR = 1.3, 95% CI 1.2, 1.3) and high (aRR = 1.5, 95% CI 1.5, 1.6) NSED compared to low NSED was associated with inadequate weight gain while NSED was not associated with excessive weight gain. Among black women, high versus low NSED was associated with weight loss during pregnancy (RR = 1.6, 95% CI 1.1, 2.5). Among white women, each level of NSED compared to low NSED was associated with weight loss during pregnancy. This study demonstrates how neighborhood socioeconomic characteristics can contribute to our understanding of inadequate weight gain and weight loss during pregnancy, having implications for future research and interventions designed to advance pregnancy outcomes.

Contribution of psychopathology, psychosocial problems and substance use to urban and rural differences in birth outcomes

BACKGROUND

Urban residence contributes to disparities in preterm birth (PTB) and birth weight. As urban and rural pregnant populations differ in individual psychopathological, psychosocial and substance use (PPS) risks, we examined the extent to which PTB and birth weight depend on the (accumulative) effect of PPS risk factors and on demographic variation.

METHODS

Follow-up study from 2010 to 2012 among 689 urban and 348 rural pregnant women. Urbanity was based on the population density per ZIP code. Women completed the validated Mind2Care instrument questionnaire, which includes the Edinburgh Depression Scale, and demographic, obstetric and PPS questions. Pregnancy outcomes were extracted from medical records. With regression analyses we assessed crude and adjusted associations between residence and birth outcomes, adjusted for available confounding or mediating factors.

RESULTS

PTB was significantly associated with segregation, maternal age (<25 and ≥ 35 years old), primiparity, smoking during pregnancy and the accumulation of risks, but not with residence (urban, 4%; rural, 7%; P = 0.16). Mean birth weight was significantly lower for urban babies (crude β: -174; P < 0.001). Adjusting for potential confounders and mediators, non-Western ethnicity, parity and smoking during pregnancy significantly decreased birth weight besides residence. The accumulative effect of PPS risk factors significantly decreased birth weight (β: -58 g per risk factor; P < 0.001).

CONCLUSION

PTB was not associated with residence. The lower birth weight of urban babies remains significant after adjusting for urban risks, such as non-Western ethnicity and the PPS risk factor smoking. The accumulation of multiple (moderate) PPS risks accounts partly for the urban effect.

Deprived neighborhoods and adverse perinatal outcome: a systematic review and meta-analysis

OBJECTIVES

This study aims to summarize evidence on the relation between neighborhood deprivation and the risks for preterm birth, small-for-gestational age, and stillbirth.

DESIGN

The design was a systematic review and meta-analysis.

MAIN OUTCOME MEASURES

The main outcome measures included studies that directly compared the risk of living in the most deprived neighborhood quintile with least deprived quintile for at least one perinatal outcome of interest (preterm delivery, small-for-gestational age and stillbirth).

METHODS

Study selection was based on a search of Medline, Embase and Web of Science for articles published up to April 2012, reference list screening, and email contact with authors. Data on study characteristics, outcome measures, and quality were extracted by two independent investigators. Random-effects meta-analysis was performed to estimate unadjusted and adjusted summary odds ratios with the associated 95% confidence intervals.

RESULTS

We identified 2863 articles, of which 24 were included in a systematic review. A meta-analysis (n = 7 studies, including 2 579 032 pregnancies) assessed the risk of adverse perinatal outcomes by comparing the most deprived neighborhood quintile with the least deprived quintile. Compared with the least deprived quintile, odds ratios for adverse perinatal outcomes in the most deprived neighborhood quintile were significantly increased for preterm delivery (odds ratio 1.23, 95% confidence interval 1.18-1.28), small-for-gestational age (odds ratio 1.31, 95% confidence interval 1.28-1.34), and stillbirth (odds ratio 1.33, 95% confidence interval 1.21-1.45).

CONCLUSIONS

Living in a deprived neighborhood is associated with preterm birth, small-for-gestational age and stillbirth.

Does area deprivation modify the association between exposure to a nitrate and low-dose atrazine metabolite mixture in drinking water and small for gestational age? A historic cohort study

Birth weight may be influenced by environmental and socio-economic factors that could interact. The main objective of our research was to investigate whether area deprivation may modify the association between drinking water exposure to a mixture of atrazine metabolites and nitrates during the second trimester of pregnancy and prevalence of small for gestational age (SGA) neonates. We conducted a historic cohort study in Deux-Sèvres, France between 2005 and 2010, using birth records, population census and regularly performed drinking water withdrawals at community water systems. Exposure to an atrazine metabolite/nitrate mixture in drinking water was divided into six classes according to the presence or absence of atrazine metabolites and to the terciles of nitrate concentrations in each trimester of pregnancy. We used a logistic regression to model the association between SGA and mixture exposure at the second trimester while taking into account the area deprivation measured by the Townsend index as an effect modifier and controlling for the usual confounders. We included 10,784 woman-neonate couples. The risk of SGA when exposed to second tercile of nitrate without atrazine metabolites was significantly greater in women living in less deprived areas (OR = 2.99; 95 % CI (1.14, 7.89)), whereas it was not significant in moderately and more deprived areas. One of the arguments used to explain this result is the presence of competing risk factors in poorer districts.

Does centralisation of acute obstetric care reduce intrapartum and first-week mortality? An empirical study of over 1 million births in the Netherlands

In this hypothetical analysis with retrospective cohort data (1,160,708 hospital births) we estimated outcome of centralisation of acute obstetric care, i.e., closure of 10 hospitals (out of 99) in The Netherlands. The main outcome was predicted intrapartum and first-week mortality (further referred to as neonatal mortality) for several subgroups of patients affected by two centralisation scenarios: (1) closure of the 10 smallest hospitals; (2) closure of the 10 smallest hospitals, but avoiding adjacent closures. Predictions followed from regression coefficients from a multilevel logistic regression model. Scenario 1 resulted in doubled travel time, and 10% increased mortality (210 [0.34%] to 231 [0.38%] cases). Scenario 2 showed less effect on mortality (268 [0.33%] to 259 [0.32%] cases) and travel time. Heterogeneity in hospital organisational features caused simultaneous improvement and deterioration of predicted neonatal mortality. Consequences vary for subgroups. We demonstrate that (in The Netherlands) centralisation of acute obstetric care according to the 'closure-of-the-smallest-rule' yields suboptimal outcomes. In order to develop an optimal strategy one would need to consider all positive and negative effects, e.g., organisational heterogeneity of closing and surviving hospitals, differential effects for patient subgroups, increased travel time, and financial aspects. The provided framework may be beneficial for other countries considering centralisation of acute obstetric care.

Patient versus professional based psychosocial risk factor screening for adverse pregnancy outcomes

To identify Psychopathology, Psychosocial problems and substance use (PPS) as predictors of adverse pregnancy outcomes, two screen-and-advice instruments were developed: Mind2Care (M2C, self-report) and Rotterdam Reproductive Risk Reduction (R4U, professional's checklist). To decide on the best clinical approach of these risks, the performance of both instruments was compared. Observational study of 164 pregnant women who booked at two midwifery practices in Rotterdam. Women were consecutively screened with M2C and R4U. For referral to tailored care based on specific PPS risks, inter-test agreement of single risks was performed in terms of overall accuracy and positive accuracy (risk present according to both instruments). With univariate regression analysis we explored determinants of poor agreement (<90 %). For triage based on risk accumulation and for detecting women-at-risk for adverse birth outcomes, M2C and R4U sum scores were compared. Overall accuracy of single risks was high (mean 93 %). Positive accuracy was lower (mean 46 %) with poorest accuracy for current psychiatric symptoms. Educational level and ethnicity partly explained poor accuracy (p < 0.05). Overall low PPS prevalence decreased the statistical power. For triage, M2C and R4U sum scores were interchangeable from sum scores of five or more (difference <1 %). The probability of adverse birth outcomes similarly increased with risk accumulation for both instruments, identifying 55-75 % of women-at-risk. The self-report M2C and the professional's R4U checklist seem interchangeable for triage of women-at-risk for PPS or adverse birth outcomes. However, the instruments seem to provide complementary information if used as a guidance to tailored risk-specific care.

The Rotterdam Study: 2014 objectives and design update

The Rotterdam Study is a prospective cohort study ongoing since 1990 in the city of Rotterdam in The Netherlands. The study targets cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, oncological, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. The findings of the Rotterdam Study have been presented in over a 1,000 research articles and reports (see www.erasmus-epidemiology.nl/rotterdamstudy ). This article gives the rationale of the study and its design. It also presents a summary of the major findings and an update of the objectives and methods.

Social deprivation and adverse perinatal outcomes among Western and non-Western pregnant women in a Dutch urban population

Social deprivation is considered a key factor in adverse perinatal outcomes. Rotterdam, the second largest city in The Netherlands, has large inequalities in perinatal health and a high number of deprived neighbourhoods. Social deprivation is measured here through a composite variable: 'Social Index' (SI). We studied the impact of the SI (2008-2009; 5 categories) in terms of perinatal mortality, congenital anomalies, preterm birth, small for gestational age (SGA) and low 5-minute Apgar score as registered in The Netherlands Perinatal Registry (Rotterdam 2000-2007, n = 56,443 singleton pregnancies). We applied ethnic dichotomisation as Western (European/North-American/Australian) vs. Non-Western (all others) ethnicity was expected to interact with the impact of SI. Tests for trend and multilevel regression analysis were applied. Gradually decreasing prevalence of adverse perinatal outcomes was observed in Western women from the lowest SI category (low social quality) to the highest SI category (high social quality). In Western women the low-high SI gradient for prevalence of spontaneous preterm birth (per 1000) changed from 57.2 to 34.1, for iatrogenic preterm birth from 35.2 to 19.0, for SGA from 119.6 to 59.4, for low Apgar score from 10.9 to 8.2, and for perinatal mortality from 14.9 to 7.6. These trends were statistically confirmed by Chi2-tests for trend (p < 0.001). For non-Western women such trends were absent. These strong effects for Western women were confirmed by significant odds ratios for almost all adverse perinatal outcomes estimated from multilevel regression analysis. We conclude social deprivation to play a different role among Western vs. non-Western women. Our results suggest that improvements in social quality may improve perinatal outcomes in Western women, but alternative approaches may be necessary for non-Western groups. Suggested explanations for non-Western 'migrant' groups include the presence of 'protective' effects through knowledge systems or intrinsic resilience. Implications concern both general and targeted policies.

The association of neighbourhood and individual social capital with consistent self-rated health: a longitudinal study in Brazilian pregnant and postpartum women

BACKGROUND

Social conditions, social relationships and neighbourhood environment, the components of social capital, are important determinants of health. The objective of this study was to investigate the association of neighbourhood and individual social capital with consistent self-rated health in women between the first trimester of pregnancy and six months postpartum.

METHODS

A multilevel cohort study in 34 neighbourhoods was performed on 685 Brazilian women recruited at antenatal units in two cities in the State of Rio de Janeiro, Brazil. Self-rated health (SRH) was assessed in the 1st trimester of pregnancy (baseline) and six months after childbirth (follow-up). The participants were divided into two groups: 1. Good SRH--good SRH at baseline and follow-up, and, 2. Poor SRH--poor SRH at baseline and follow-up. Exploratory variables collected at baseline included neighbourhood social capital (neighbourhood-level variable), individual social capital (social support and social networks), demographic and socioeconomic characteristics, health-related behaviours and self-reported diseases. A hierarchical binomial multilevel analysis was performed to test the association between neighbourhood and individual social capital and SRH, adjusted for covariates.

RESULTS

The Good SRH group reported higher scores of social support and social networks than the Poor SRH group. Although low neighbourhood social capital was associated with poor SRH in crude analysis, the association was not significant when individual socio-demographic variables were included in the model. In the final model, women reporting poor SRH both at baseline and follow-up had lower levels of social support (positive social interaction) [OR 0.82 (95% CI: 0.73-0.90)] and a lower likelihood of friendship social networks [OR 0.61 (95% CI: 0.37-0.99)] than the Good SRH group. The characteristics that remained associated with poor SRH were low level of schooling, Black and Brown ethnicity, more children, urinary infection and water plumbing outside the house.

CONCLUSIONS

Low individual social capital during pregnancy, considered here as social support and social network, was independently associated with poor SRH in women whereas neighbourhood social capital did not affect women's SRH during pregnancy and the months thereafter. From pregnancy and up to six months postpartum, the effect of individual social capital explained better the consistency of SRH over time than neighbourhood social capital.

The Generation R Study: design and cohort update 2012

The Generation R Study is a population-based prospective cohort study from fetal life until adulthood. The study is designed to identify early environmental and genetic causes and causal pathways leading to normal and abnormal growth, development and health during fetal life, childhood and adulthood. The study focuses on six areas of research: (1) maternal health; (2) growth and physical development; (3) behavioural and cognitive development; (4) respiratory health and allergies; (5) diseases in childhood; and (6) health and healthcare for children and their parents. Main exposures of interest include environmental, endocrine, genetic and epigenetic, lifestyle related, nutritional and socio-demographic determinants. In total, n = 9,778 mothers with a delivery date from April 2002 until January 2006 were enrolled in the study. Response at baseline was 61 %, and general follow-up rates until the age of 6 years exceed 80 %. Data collection in mothers, fathers and children include questionnaires, detailed physical and ultrasound examinations, behavioural observations, and biological samples. A genome and epigenome wide association screen is available in the participating children. From the age of 5 years, regular detailed hands-on assessments are performed in a dedicated research center including advanced imaging facilities such as Magnetic Resonance Imaging. Eventually, results forthcoming from the Generation R Study contribute to the development of strategies for optimizing health and healthcare for pregnant women and children.

Meta-Analysis of Maternal and Neonatal Outcomes Associated with the Use of Insulin Glargine versus NPH Insulin during Pregnancy

As glargine, an analog of human insulin, is increasingly used during pregnancy, a meta-analysis assessed its safety in this population. A systematic literature search identified studies of gestational or pregestational diabetes comparing use of insulin glargine with human NPH insulin, with at least 15 women in both arms. Data was extracted for maternal outcomes (weight at delivery, weight gain, 1st/3rd trimester HbA_1c, severe hypoglycemia, gestation/new-onset hypertension, preeclampsia, and cesarean section) and neonatal outcomes (congenital malformations, gestational age at delivery, birth weight, macrosomia, LGA, 5 minute Apgar score >7, NICU admissions, respiratory distress syndrome, neonatal hypoglycemia, and hyperbilirubinemia). Relative risk ratios and weighted mean differences were determined using a random effect model. Eight studies of women using glargine (331) or NPH (371) were analyzed. No significant differences in the efficacy and safety-related outcomes were found between glargine and NPH use during pregnancy.

Fetal and infant origins of asthma

Previous studies have suggested that asthma, like other common diseases, has at least part of its origin early in life. Low birth weight has been shown to be associated with increased risks of asthma, chronic obstructive airway disease, and impaired lung function in adults, and increased risks of respiratory symptoms in early childhood. The developmental plasticity hypothesis suggests that the associations between low birth weight and diseases in later life are explained by adaptation mechanisms in fetal life and infancy in response to various adverse exposures. Various pathways leading from adverse fetal and infant exposures to growth adaptations and respiratory health outcomes have been studied, including fetal and early infant growth patterns, maternal smoking and diet, children's diet, respiratory tract infections and acetaminophen use, and genetic susceptibility. Still, the specific adverse exposures in fetal and early postnatal life leading to respiratory disease in adult life are not yet fully understood. Current studies suggest that both environmental and genetic factors in various periods of life, and their epigenetic mechanisms may underlie the complex associations of low birth weight with respiratory disease in later life. New well-designed epidemiological studies are needed to identify the specific underlying mechanisms. This review is focused on specific adverse fetal and infant growth patterns and exposures, genetic susceptibility, possible respiratory adaptations and perspectives for new studies.