Maternal age and low birth weight: a reinterpretation of their association under a demographic transition in southern Brazil

Temporal evolution of the risk factors associated with low birth weight rates in Brazilian capitals (1996-2011)

Objective

To analyze the trend of low birth weight (LBW) and its determinants in Brazilian state capitals between 1996 and 2011. We intended to determine which variables are associated with LBW during the period studied.

Methods

This is a cross-sectional study that used data from the National Information System of Live Births from 26 state capitals and Brasilia (the federal capital), divided into five geographical regions. The Average Annual Percentage of Change (AAPC) was used to assess the possible time trend in the low birth weight rates for considering all regions together and each region separately, according to each variable, and the Poisson regression was calculated in order to demonstrate time trends in low birth weight and the impact of variables (age and educational maternal level, antenatal visits, type of delivery, and gestational age) during the period. All variables were analyzed together using the Poisson regression as well.

Results

From the total of 11,200,255 live births used in this study, there was a significant reduction in the number of live births, especially in the more developed regions. The low birth weight rate was 8 %, and it was stable during the period. Considering regional trends, the rate was higher in the Southeast and South regions, and significantly higher in the North, Northeast, and Central West regions. Improvements in maternal education and antenatal care coverage reduced the risk for low birth weight in all regions. Also, there was an increase in caesarean sections in all regions, with a small impact on low birth weight rates.

Conclusions

Improvements in education and health care reduced the risk for low birth weight in all Brazilian regions during the period of study. Trends in low birth weight rates and the associated factors differ from region to region, showing different stages of demographic, epidemiological and developmental transition in Brazil. The present study was approved by the Research Ethics Committee at the Hospital de Clínicas de Porto Alegre (Protocol 120323).

Cesarean delivery and metabolic risk factors in young adults: a Brazilian birth cohort study

BACKGROUND

Cesarean delivery (CD) perturbs the assembly of the neonatal gut microbiome and has been associated with child and adult obesity. However, it is still unknown whether CD is associated with metabolic risk factors in young adults.

OBJECTIVE

We investigated the association of CD and metabolic risk factors in young adults in a cohort study who were 23-25 y of age at follow-up.

DESIGN

We used data from a cohort study in Ribeirão Preto, Brazil. Baseline data on 6827 singleton pregnancies were collected in 1978-1979, and a sample of 2063 subjects were followed up 23-25 y later (2002-2004). Information on the type of delivery, birth weight, maternal age, parity, maternal schooling, and maternal smoking was obtained after birth. Anthropometric data, biochemical measurements, and information on participant schooling and smoking history were collected at 23-25 y of age. A linear regression was performed to assess the association between CD and biochemical measurements in early adulthood, controlling for a minimum set of confounders that were identified in a directed acyclic graph.

RESULTS

The mean ± SD age of the subjects was 23.9 ± 0.71 y, and 51.8% of the sample were women. The CD rate was 32.0% and was more common in older (P < 0.001) and more educated mothers (P < 0.001). Compared with vaginal delivery, CD was associated with higher body mass index (BMI) after multivariable adjustment (P < 0.001) but not with glucose, homeostasis model assessment of insulin resistance, the quantitative insulin-sensitivity check index, total cholesterol, LDL cholesterol, HDL cholesterol, or triglycerides (all P > 0.05).

CONCLUSION

In our sample of Brazilian adults, CD was associated with higher BMI but not with other metabolic risk factors.

Risk Assessment of Adverse Birth Outcomes in Relation to Maternal Age

BACKGROUND

Although a number of studies have investigated correlations of maternal age with birth outcomes, an extensive assessment using age as a continuous variable is lacking. In the current study, we estimated age-specific risks of adverse birth outcomes in childbearing women.

METHOD

National population-based data containing maternal and neonatal information were derived from the Health Promotion Administration, Taiwan. A composite adverse birth outcome was defined as at least anyone of stillbirth, preterm birth, low birth weight, macrosomia, neonatal death, congenital anomaly, and small for gestational age (SGA). Singletons were further analyzed for outcomes of live birth in relation to each year of maternal age. A log-binomial model was used to adjust for possible confounders of maternal and neonatal factors.

RESULTS

In total, 2,123,751 births between 2001 and 2010 were utilized in the analysis. The risk of a composite adverse birth outcome was significantly higher at extreme maternal ages. In specific, risks of stillbirth, neonatal death, preterm birth, congenital anomaly, and low birth weight were higher at the extremes of maternal age. Furthermore, risk of macrosomia rose proportionally with an increasing maternal age. In contrast, risk of SGA declined proportionally with an increasing maternal age. The log-binomial model showed greater risks at the maternal ages of <26 and > 30 years for a composite adverse birth outcome.

CONCLUSIONS

Infants born to teenagers and women at advanced age possess greater risks for stillbirth, preterm birth, neonatal death, congenital anomaly, and low birth weight. Pregnancies at advanced age carry an additional risk for macrosomia, while teenage pregnancies carry an additional risk for SGA. The data suggest that the optimal maternal ages to minimize adverse birth outcomes are 26∼30 years.