Fetal adrenal gland with flat-lying sign is an imaging presentation that focuses on ectopic, absent, or underdeveloped fetal kidneys, and is seen on imaging with the ipsilateral adrenal gland appearing to lie flat behind the psoas muscle. The adrenal gland is one of the more important endocrine organs in the human body, and its normal position is above the kidneys, one in each of the left and right kidneys, wrapped by adipose tissue and renal fascia. However, in cases of renal agenesis, renal ectasia, or renal hypoplasia, the adrenal glands lack support and may appear to express the flatus sign image. If the fetal ipsilateral kidney is absent, the ipsilateral adrenal gland will lose its support, and its position will be changed, resulting in the flat-lying sign; if one of the fetal kidneys is underdeveloped, which is unable to support the adrenal gland, the position of the adrenal gland may also be shifted, and the adrenal gland gradually appears to lie flat on the posterior aspect of the psoas muscle; if the kidney is ectopic, the adrenal gland that depends on the adrenal gland may be shifted in position as well. If the fetal adrenal glands are lying flat, you should go to the regular hospital as soon as possible to complete the examination, clarify the cause of the disease, and carry out targeted treatment under the guidance of physicians.