Many congenital heart defects can be diagnosed prenatally by fetal echocardiography. Triple X syndrome can be diagnosed prenatally through amniocentesis or chorionic villus sampling. These studies indicate that large microcystic lesions may be treated prenatally without surgical intervention. It is sometimes diagnosed prenatally by a nuchal scan or post-natally by lymphoscintigraphy. Rats have been used in experimental manipulations of intelligence using chemicals administered prenatally. The prosencephalon or forebrain is the embryonic structure from which the cerebrum develops prenatally. Of these, approximately 30% are diagnosed prenatally. Both prenatally exposed groups suffered lower cognitive abilities and reduced employment levels. The subjects were exposed to famine prenatally but not after birth. Ultrasound remains as one of the only effective ways of prenatally diagnosing Larsen syndrome. Surgery is not required in all prenatally detected cases. Bladder mucosa is one of the tissues that express high levels of H19 RNA prenatally. Reinisch cited several cases of "male feminization" among prenatally DES-exposed males. In some cases, it can be detected prenatally. There was also an effect on the corticosterone secretion for prenatally stressed females.