Implementation of the INTERGROWTH-21st Project in Brazil

Etiologically Based Functional Taxonomy of the Preterm Birth Syndrome

Preterm birth (PTB) is a complex syndrome traditionally defined by a single parameter, namely, gestational age at birth (ie, ˂37 weeks). This approach has limitations for clinical usefulness and may explain the lack of progress in identifying cause-specific effective interventions. The authors offer a framework for a functional taxonomy of PTB based on (1) conceptual principles established a priori; (2) known etiologic factors; (3) specific, prospectively identified obstetric and neonatal clinical phenotypes; and (4) postnatal follow-up of growth and development up to 2 years of age. This taxonomy includes maternal, placental, and fetal conditions routinely recorded in data collection systems.

Recruitment and retention of pregnant women in prospective birth cohort studies: A scoping review and content analysis of the literature

Longitudinal cohort studies present unique methodological challenges, especially when they focus on vulnerable populations, such as pregnant women. The purpose of this review is to synthesize the existing knowledge on recruitment and retention (RR) of pregnant women in birth cohort studies and to make recommendations for researchers to improve research engagement of this population. A scoping review and content analysis were conducted to identify facilitators and barriers to the RR of pregnant women in cohort studies. The search retrieved 574 articles, with 38 meeting eligibility criteria and focused on RR among English-speaking, adult women, who are pregnant or in early postpartum period, enrolled in birth cohort studies. Selected studies were birth cohort (including longitudinal) (n = 20), feasibility (n = 14), and other (n = 4) non-interventional study designs. The majority were from low-risk populations. Abstracted data were coded according to emergent theme clusters. The majority of abstracted data (79%) focused on recruitment practices, with only 21% addressing retention strategies. Overall, facilitators were reported more often (75%) than barriers (25%). Building trusting relationships and employing diverse recruitment methods emerged as major recruitment facilitators; major barriers included heterogeneous participant reasons for refusal and cultural factors. Key retention facilitators included flexibility with scheduling, frequent communication, and culturally sensitive practices, whereas participant factors such as loss of interest, pregnancy loss, relocation, multiple caregiver shifts, and substance use/psychiatric problems were cited as major barriers. Better understanding of facilitators and barriers of RR can help enhance the internal and external validity of future birth/pre-birth cohorts. Strategies presented in this review can help inform investigators and funding agencies of best practices for RR of pregnant women in longitudinal studies.

Brazilian cohorts with potential for life-course studies: a scoping review

OBJECTIVE To identify the Brazilian cohorts that started either in the prenatal period or at birth, to describe their characteristics and the explored variables, and to map the cohorts with potential for studies on early determinants on health and the risk of falling ill on later stages of the life cycle. METHODS A scoping review was carried out. The articles were searched in the electronic databases PubMed and Virtual Health Library (VHL). The descriptors used were [((("Child" OR "Child, Preschool" OR "Infant" OR "Infant, Newborn") AND (Cohort Studies" OR "Longitudinal Studies")) AND "Brazil")]. The inclusion criteria were Brazilian cohorts that started the baseline in the prenatal period or at birth and with at least two follow-ups with the participants. In order to meet the concept of LCE, we excluded those cohorts whose follow-ups were restricted to the first year of life, as well as those that did not address biological, behavioral and psychosocial aspects, and cohorts with data collection of a single stage of the life cycle. RESULTS The search step identified 5,010 articles. Eighteen cohorts were selected for descriptive synthesis. The median number of baseline participants was 2,000 individuals and the median age at the last follow-up was 9 years. Sample loss at the last follow-up ranged from 9.2 to 87.5%. Most cohorts monitored two phases of the life cycle (the perinatal period and childhood). The Southern region had the highest number of cohorts. The main variables collected were sociodemographic and environmental aspects of the family, morbidity aspects, nutritional practices and lifestyle. CONCLUSIONS We recommend the continuity of these cohorts, the approach to different social contexts and the performance of follow-ups with participants in different phases of the life cycle for the strengthening and expansion of life course epidemiology analyses in Brazil.

Deep clinical and biological phenotyping of the preterm birth and small for gestational age syndromes: The INTERBIO-21 st Newborn Case-Control Study protocol

Background: INTERBIO-21 ^st is Phase II of the INTERGROWTH-21 ^st Project, the population-based, research initiative involving nearly 70,000 mothers and babies worldwide coordinated by Oxford University and performed by a multidisciplinary network of more than 400 healthcare professionals and scientists from 35 institutions in 21 countries worldwide. Phase I, conducted 2008-2015, consisted of nine complementary studies designed to describe optimal human growth and neurodevelopment, based conceptually on the WHO prescriptive approach. The studies generated a set of international standards for monitoring growth and neurodevelopment, which complement the existing WHO Child Growth Standards. Phase II aims to improve the functional classification of the highly heterogenous preterm birth and fetal growth restriction syndromes through a better understanding of how environmental exposures, clinical conditions and nutrition influence patterns of human growth from conception to childhood, as well as specific neurodevelopmental domains and associated behaviors at 2 years of age.

Methods: In the INTERBIO-21 ^st Newborn Case-Control Study, a major component of Phase II, our objective is to investigate the mechanisms potentially responsible for preterm birth and small for gestational age and their interactions, using deep phenotyping of clinical, growth and epidemiological data and associated nutritional, biochemical, omic and histological profiles. Here we describe the study sites, population characteristics, study design, methodology and standardization procedures for the collection of longitudinal clinical data and biological samples (maternal blood, umbilical cord blood, placental tissue, maternal feces and infant buccal swabs) for the study that was conducted between 2012 and 2018 in Brazil, Kenya, Pakistan, South Africa, Thailand and the UK.

Discussion: Our study provides a unique resource for the planned analyses given the range of potentially disadvantageous exposures (including poor nutrition, pregnancy complications and infections) in geographically diverse populations worldwide. The study should enhance current medical knowledge and provide new insights into environmental influences on human growth and neurodevelopment.

Deep clinical and biological phenotyping of the preterm birth and small for gestational age syndromes: The INTERBIO-21 st Newborn Case-Control Study protocol

Background: INTERBIO-21 ^st is Phase II of the INTERGROWTH-21 ^st Project, the population-based, research initiative involving nearly 70,000 mothers and babies worldwide coordinated by Oxford University and performed by a multidisciplinary network of more than 400 healthcare professionals and scientists from 35 institutions in 21 countries worldwide. Phase I, conducted 2008-2015, consisted of nine complementary studies designed to describe optimal human growth and neurodevelopment, based conceptually on the WHO prescriptive approach. The studies generated a set of international standards for monitoring growth and neurodevelopment, which complement the existing WHO Child Growth Standards. Phase II aims to improve the functional classification of the highly heterogenous preterm birth and fetal growth restriction syndromes through a better understanding of how environmental exposures, clinical conditions and nutrition influence patterns of human growth from conception to childhood, as well as specific neurodevelopmental domains and associated behaviors at 2 years of age. Methods: In the INTERBIO-21 ^st Newborn Case-Control Study, a major component of Phase II, our objective is to investigate the mechanisms potentially responsible for preterm birth and small for gestational age and their interactions, using deep phenotyping of clinical, growth and epidemiological data and associated nutritional, biochemical, omic and histological profiles. Here we describe the study sites, population characteristics, study design, methodology and standardization procedures for the collection of longitudinal clinical data and biological samples (maternal blood, umbilical cord blood, placental tissue, maternal feces and infant buccal swabs) for the study that was conducted between 2012 and 2018 in Brazil, Kenya, Pakistan, South Africa, Thailand and the UK. Discussion: Our study provides a unique resource for the planned analyses given the range of potentially disadvantageous exposures (including poor nutrition, pregnancy complications and infections) in geographically diverse populations worldwide. The study should enhance current medical knowledge and provide new insights into environmental influences on human growth and neurodevelopment.

Socioeconomic inequality in preterm birth in four Brazilian birth cohort studies

OBJECTIVE

To analyze economic inequality (absolute and relative) due to family income in relation to the occurrence of preterm births in Southern Brazil.

METHODS

Four birth cohort studies were conducted in the years 1982, 1993, 2004, and 2011. The main exposure was monthly family income and the primary outcome was preterm birth. The inequalities were calculated using the slope index of inequality and the relative index of inequality, adjusted for maternal skin color, education, age, and marital status.

RESULTS

The prevalence of preterm births increased from 5.8% to approximately 14% (p-trend<0.001). Late preterm births comprised the highest proportion among the preterm births in all studies, although their rates decreased over the years. The analysis on the slope index of inequality demonstrated that income inequality arose in the 1993, 2004, and 2011 studies. After adjustment, only the 2004 study maintained the difference between the poorest and the richest subjects, which was 6.3 percentage points. The relative index of inequality showed that, in all studies, the poorest mothers were more likely to have preterm newborns than the richest. After adjustment for confounding factors, it was observed that the poorest mothers only had a greater chance of this outcome in 2004.

CONCLUSION

In a final model, economic inequalities resulting from income were found in relation to preterm births only in 2004, although a higher prevalence of prematurity continued to be observed in the poorest population, in all the studies.

The antepartum stillbirth syndrome: risk factors and pregnancy conditions identified from the INTERGROWTH-21st Project

OBJECTIVES

To identify risk factors for antepartum stillbirth, including fetal growth restriction, among women with well-dated pregnancies and access to antenatal care.

DESIGN

Population-based, prospective, observational study.

SETTING

Eight international urban populations.

POPULATION

Pregnant women and their babies enrolled in the Newborn Cross-Sectional Study of the INTERGROWTH-21^st Project.

METHODS

Cox proportional hazard models were used to compare risks among antepartum stillborn and liveborn babies.

MAIN OUTCOME MEASURES

Antepartum stillbirth was defined as any fetal death after 16 weeks' gestation before the onset of labour.

RESULTS

Of 60 121 babies, 553 were stillborn (9.2 per 1000 births), of which 445 were antepartum deaths (7.4 per 1000 births). After adjustment for site, risk factors were low socio-economic status, hazard ratio (HR): 1.6 (95% CI, 1.2-2.1); single marital status, HR 2.0 (95% CI, 1.4-2.8); age ≥40 years, HR 2.2 (95% CI, 1.4-3.7); essential hypertension, HR 4.0 (95% CI, 2.7-5.9); HIV/AIDS, HR 4.3 (95% CI, 2.0-9.1); pre-eclampsia, HR 1.6 (95% CI, 1.1-3.8); multiple pregnancy, HR 3.3 (95% CI, 2.0-5.6); and antepartum haemorrhage, HR 3.3 (95% CI, 2.5-4.5). Birth weight <3rd centile was associated with antepartum stillbirth [HR, 4.6 (95% CI, 3.4-6.2)]. The greatest risk was seen in babies not suspected to have been growth restricted antenatally, with an HR of 5.0 (95% CI, 3.6-7.0). The population-attributable risk of antepartum death associated with small-for-gestational-age neonates diagnosed at birth was 11%.

CONCLUSIONS

Antepartum stillbirth is a complex syndrome associated with several risk factors. Although small babies are at higher risk, current growth restriction detection strategies only modestly reduced the rate of stillbirth.

TWEETABLE ABSTRACT

International stillbirth study finds individual risks poor predictors of death but combinations promising.

Prevalence and risk factors related to preterm birth in Brazil

BACKGROUND

The rate of preterm birth has been increasing worldwide, including in Brazil. This constitutes a significant public health challenge because of the higher levels of morbidity and mortality and long-term health effects associated with preterm birth. This study describes and quantifies factors affecting spontaneous and provider-initiated preterm birth in Brazil.

METHODS

Data are from the 2011-2012 "Birth in Brazil" study, which used a national population-based sample of 23,940 women. We analyzed the variables following a three-level hierarchical methodology. For each level, we performed non-conditional multiple logistic regression for both spontaneous and provider-initiated preterm birth.

RESULTS

The rate of preterm birth was 11.5 %, (95 % confidence 10.3 % to 12.9 %) 60.7 % spontaneous - with spontaneous onset of labor or premature preterm rupture of membranes - and 39.3 % provider-initiated, with more than 90 % of the last group being pre-labor cesarean deliveries. Socio-demographic factors associated with spontaneous preterm birth were adolescent pregnancy, low total years of schooling, and inadequate prenatal care. Other risk factors were previous preterm birth (OR 3.74; 95 % CI 2.92-4.79), multiple pregnancy (OR 16.42; 95 % CI 10.56-25.53), abruptio placentae (OR 2.38; 95 % CI 1.27-4.47) and infections (OR 4.89; 95 % CI 1.72-13.88). In contrast, provider-initiated preterm birth was associated with private childbirth healthcare (OR 1.47; 95 % CI 1.09-1.97), advanced-age pregnancy (OR 1.27; 95 % CI 1.01-1.59), two or more prior cesarean deliveries (OR 1.64; 95 % CI 1.19-2.26), multiple pregnancy (OR 20.29; 95 % CI 12.58-32.72) and any maternal or fetal pathology (OR 6.84; 95 % CI 5.56-8.42).

CONCLUSION

The high proportion of provider-initiated preterm birth and its association with prior cesarean deliveries and all of the studied maternal/fetal pathologies suggest that a reduction of this type of prematurity may be possible. The association of spontaneous preterm birth with socially-disadvantaged groups reaffirms that the reduction of social and health inequalities should continue to be a national priority.

LBW and IUGR temporal trend in 4 population-based birth cohorts: the role of economic inequality

Background

Low/medium income countries, with health inequalities present high rates of neonates having low birthweight and/or are small for the gestational age. This study aims to analyze the absolute and relative income inequality in the occurrence of low birthweight and small size for gestational age among neonates in four birth cohorts from southern Brazil in 1982, 1993, 2004, and 2011.

Methods

The main exhibit was monthly family income. The outcomes were birth with low birthweight or small for the gestational age. The inequalities were calculated using the Slope Index of Inequality and the Relative Index of Inequality adjusted for maternal skin color, schooling, age, and marital status.

Results

In all birth cohorts, poorer mothers were at greater odds of having neonates with low birthweight or small for the gestational age. There was a tendency to decrease the prevalence of small for gestational age in poorer families associated with the reduction of inequalities over the past decades, which was not observed regarding low birthweight.

Conclusions

Economic inequalities occurred in neonates with low birthweight and with intrauterine growth restriction in the four studies, with a higher incidence of inadequate neonatal outcomes in the poorer families.

Determining gestational age based on information from the Birth in Brazil study

This study aimed at assessing the validity of different measures for estimating gestational age and to propose the creation of an algorithm for gestational age at birth estimates for the Birth in Brazil survey--a study conducted in 2011-2012 with 23,940 postpartum women. We used early ultrasound imaging, performed between 7-20 weeks of gestation, as the reference method. All analyses were performed stratifying by payment of maternity care (public or private). When compared to early ultrasound imaging, we found a substantial intraclass correlation coefficient of ultrasound-based gestational age at admission measure (0.95 and 0.94) and of gestational age reported by postpartum women at interview measure (0.90 and 0.88) for the public and private payment of maternity care, respectively. Last menstrual period-based measures had lower intraclass correlation coefficients than the first two measures evaluated. This study suggests caution when using the last menstrual period as the first measure for estimating gestational age in Brazil, strengthening the use of information obtained from early ultrasound imaging results.

[Prevalence of preterm birth according to birth weight group: a systematic review]

OBJECTIVE

To estimate the prevalence of preterm birth by categories of birth weight, and to obtain an equation to correct the estimates.

METHODS

Systematic review of the Brazilian literature published from 1990 to 2012, to identify studies with primary collection of data on birth weight and gestational age. Twelve studies were selected and contributed for tabulations of preterm prevalence according to 100 g birth weight categories. These results were combined using sex-specific fractional polynomial equations and the resulting curves were compared with results from the Live Birth Information System for the years 2000, 2005, 2010 and 2011.

RESULTS

For all birth weight categories, preterm prevalence estimates based on primary studies had a higher prevalence than those of the the Live Birth Information System. The prevalence reported by the Live Birth Information System was of 7.2% in 2010, about 38.0% lower than the estimated prevalence of 11.7% obtained with the correctional equation.

CONCLUSIONS

Information reported by the Live Birth Information System on preterm prevalence does not reflect the true magnitude of the problem in Brazil, and should not be used without the correction factors proposed in the present analyses.