currently, researchers are examining the correlations between maternal diet during pregnancy and its effect on the offspring's susceptibility for chronic diseases later in life. the fetal programming hypothesis highlights the idea that environmental stimuli during critical periods of fetal development can have lifelong effects on body structure and health and in a sense they prepare offspring for the environment they will be born into. many of these variations are thought to be due to epigenetic mechanisms brought on by maternal environment such as stress, diet, gestational diabetes, and exposure to tobacco and alcohol. these factors are thought to be contributing factors to obesity and cardiovascular disease, neural tube defects, cancer, diabetes, etc. studies to determine these epigenetic mechanisms are usually performed through laboratory studies of rodents and epidemiological studies of humans.