The answer lies in the discovery of DNA
While the study doesn't prove how maternal smoking may influence child development or disease, the findings suggest that DNA methylation differences might be involved in the appearance of certain birth defects or medical problems in babies born to mothers who smoke, the authors conclude in The American Journal of Human Genetics
Covariate definitions Baseline waist circumference, systolic and diastolic blood pressure, fasting glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride, estimated glomerular filtration rate, and dipstick urine albumin measurements were collected from the NHSP
They are usually caused by allergic sensitivity to airborne mold spores or to pollens from grass, trees and weeds