BACKGROUND

The radioactive component of particulate matter (PM), particle radioactivity (PR), can continue to emit radiation after inhalation. While PR has been associated with other adverse pregnancy outcomes, no studies have examined the association with fetal growth.

METHODS

Our retrospective cohort included singleton pregnancies that underwent obstetric ultrasounds at an academic medical center in Massachusetts from 2011 through 2016. PR was represented by particle gross β-activity estimated from an ensemble model and was assigned based on residential zip-code. We considered the cumulative (conception until date of fetal growth measurement) and first 16 weeks of gestation PR exposure windows. Standardized z-scores were constructed for biparietal diameter (BPD), head circumference, femur length (FL), abdominal circumference (AC), and birth weight. We used linear mixed regression models adjusted for PM ≤2.5 μm exposure, maternal sociodemographic factors, meteorological variables, and long-term trends.

RESULTS

Among 9,404 pregnancies, an interquartile range increase in cumulative PR exposure was associated with reduced BPD (-0.06 [95% CI: -0.12, -0.01] z-score) and FL (-0.06 [95% CI: -0.12, -0.01] z-score) in scans conducted before 24 weeks' gestation, with increased AC (0.05 [95% CI: 0.01, 0.09]) in scans conducted on or after 24 weeks' gestation, and with lower birth weight (-0.05 [95% CI: -0.11, -0.001] z-score). The first 16 weeks of gestation was not a critical exposure window.

CONCLUSIONS

Prenatal PR was associated with fetal growth, with associations generally negative before 24 weeks' gestation and positive later in pregnancy. Our findings bring awareness to a novel environmental exposure.