Association of birth weight with asthma‐related outcomes at age 2 years

Abstract

Summary. Background: Although lower birth weight associated with prematurity raises the risk of asthma in childhood, few prospective studies have examined higher birth weight, and few have separated the two components of birth weight, fetal growth and length of gestation.Objective. To examine the associations of fetal growth and length of gestation with asthma-related outcomes by age 2 years. Methods.We studied 1,372 infants and toddlers born after 34 weeks' gestation in Project Viva, a prospective cohort study of pregnant mothers and their children. The main outcome measures were parent report of (1) any wheezing (or whistling in the chest) from birth to age 2 years, (2) recurrent wheezing during the first 2 years of life, and (3) doctor's diagnosis of asthma, wheeze or reactive airwaydisease ("asthma") by age 2. We calculated gestational age from the last menstrual period or ultrasound examination, and determined birth weight for gestational age z-value ("fetal growth") using US national reference data.Results. Infants' mean birth weight was 3,527 (SD, 517; range, 1,559-5,528) grams. By age 2 years, 34% of children had any wheezing, 14% had recurrent wheezing, and 16% had doctor-diagnosed asthma. After adjusting for several parent, child, and household characteristics in logistic regression models, we found that infants with birth weight ≥4,000 g were not more likely to have any wheezing (odds ratio (OR), 0.91; 95% confidence interval (CI): 0.62, 1.34) or doctor-diagnosed asthma (OR, 0.80; 95% CI: 0.49, 1.31) than infants with birth weight 3,500-3,999 g. In models examining length of gestation and fetal growth separately, neither the highest nor the lowest groups of either predictor were associated with the three outcomes. Boys had a higher incidence of asthma-related outcomes than girls, and exposure to passive smoking, parental history of asthma, and exposure to older siblings were all associated with greater risk of recurrent wheeze or asthma-related outcomes at age 2 years. Conclusion.Although male sex, exposure to smoking, parental history of asthma, and exposure to older siblingswere associated with increased riskof wheezing and asthma-related outcomes in this prospective study of children born after 34 weeks gestation, fetal growth and length of gestation were not.

A Cross-Sectional Study to Find Prevalence and Risk Factors for Childhood Asthma in Pune City, India

“…Childhood asthma was more common among boys (8.1%) than girls (4.9%). The observations that asthma is more prevalent amongst boys during childhood has been reported in several earlier studies [7,8]; similar findings were reported from India [9], Italy [10], United Arab Emirates [11], and Iran [12]. The reason for male gender predominance during childhood is not known.…”

Prenatal and Passive Smoke Exposure and Incidence of Asthma and Wheeze: Systematic Review and Meta-analysis

“…19 There was insufficient data to combine the results from studies of dose-response associations; 3 studies for wheeze revealed a significant dose-response effect, 28-30 and 3 studies for asthma [31][32][33][34] revealed a significant dose-response effect; the significance could not be determined for 1 study, although the results did demonstrate increasing ORs. 32 However, 2 of the above studies also demonstrate a nonsignificant trend.…”

“…19 There was also 1 study that used an objective measure of passive smoke exposure and revealed that children with detectable cord blood levels were not at significantly increased risk of wheeze at age 1 or 3 years or of wheeze at age 3 years in relation to blood cotinine levels at age 1. 17 …”

Prospectively assessed incidence, severity, and determinants of respiratory symptoms in the first year of life

“…7,11,12 Only few studies assessed prospectively incidence of both cough and wheeze in unselected infants (Table 4). Two well-designed cohort studies out of a series from the 1980s, 13 were conducted in Colombia and Uruguay, with respiratory symptoms being assessed during regular home visits by research nurses.…”

“…In addition, most studies have been limited to wheeze, while incidence of cough has rarely been investigated. 10,11 Descriptive data on the occurrence of common respiratory symptoms in unselected European infants are therefore missing. Similarly, risk factors have only been described for wheezing disorders, but not for more common respiratory symptoms like cough.…”