GSD I is inherited in an autosomal recessive manner. People with one copy of the faulty gene are carriers of the disease and have no symptoms. As for other autosomal recessive diseases, each child born to two carriers of the disease has a 25% chance of inheriting both copies of the faulty gene and manifesting the disease. Unaffected parents of a child with GSD I can be assumed to be carriers. Prenatal diagnosis has been made by fetal liver biopsy at 18–22 weeks of gestation, but no fetal treatment has been proposed. Prenatal diagnosis is possible with fetal DNA obtained by chorionic villus sampling when a fetus is known to be at risk.