PM10 air pollution exposure during pregnancy and term low birth weight
in Allegheny County, PA, 1994-2000.
We observed a monotonic increase in the prevalence of NTDs with increasing exposure to NGD in our sensitivity analyses using 2- and 5-mile exposure radii as well as some attenuation in decreased risk for preterm birth and term low birth weight (see Supplemental Material, Tables S2-7).
We also observed small negative associations between density and proximity of natural gas wells within a 10-mile radius of maternal residence and preterm birth and term low birth weight, and a small positive association with mean birth weight.
The small negative associations with term low birth weight and preterm birth in our study population were unexpected given that other studies have reported postive associations between these outcomes and urban air pollution (Ballester et al.
To efficiently select control groups and expand the range of birth outcomes, we first constructed a stratified 10% random sample of the entire population of live births by combining the 10% sample of all term live births [greater than or equal to] 2500 g with a 10% random sample of the comprehensively identified preterm cases and term low birth weight cases (the case groups described above) (n = 4063).
We conducted a series of case--control analyses: a) stillbirths (n = 106) compared with West Virginia live births (n = 1,844) because stillbirth information was available only from West Virginia; b) pregnancy-induced hypertension rases (n = 224) compared with births without pregnancy-induced hypertension (n = 3,828); c) preterm birth cases < 37 weeks (n = 3,613) and < 32 weeks (n = 491) corresponding to all preterm and very preterm births, respectively, compared with term births (n = 3,695), with assignment based on clinical assessment of gestational age; at) term low birth weight cases (n = 918) compared with term births [greater than or equal to] 2,500 g (n = 3,616); and e) term SGA cases [births < 10th percentile by gestational age and sex (Oken et al.
PFOA was not related to risk of term low birth weight, with some suggestion of a reduced risk of SGA with higher exposure but no gradient across quintiles (Table 4).
The purpose of this study was to examine the effects of exposure to THMs and HAAs during the third trimester and during individual weeks and months of late gestation on the risks for term low birth weight, intrauterine growth retardation, and very preterm and preterm births.
In this investigation, term low birth weight and intrauterine growth retardation were not mutually exclusive, and cases born at term may have been included in both outcome groups.
They observed an approximately 10-20% increase in the risk of preterm birth (both normal and low birth weight infants) and the risk of term low birth weight in infants born to women living close to heavily traveled roadways.
Women whose third trimester fell during the fall/winter months and who were in the highest DWTD quintile had an estimated 39% greater risk of giving birth to a term low birth weight infant and a 24% greater risk of having a preterm low birth weight infant, compared to women in the lowest DWTD quintile.
The corresponding estimate from 11 studies of small-for-gestational-age births or term low birth weight