Hello and welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my opinion. Hypothyroidism, if undiagnosed and untreated, could cause not only obstetric complications, such as hypertension, preterm delivery, low birth weight, but also exposes fetus to low thyroid hormone levels. The lack of maternal thyroid hormone during early pregnancy might have some irreversible effects on fetal development . It is now clear that there is a close relationship between maternal thyroid deficiencies and the neuropsychological development of her child. Several studies demonstrated that maternal hypothyroidism was associated with impaired psychomotor and intellectual development of the child also called Cretinism. To answer to you question:In hypothyroid mother the risc of undeveloped brain is high. The most severely affected infants have neurologic cretinism, manifested by mental retardation and impaired gait and motor function Hydrocephalus that starts before a baby is born (from a hypothyroid mother )of course has to do with low thyroid hormone levels of the mother but at the same time, can be also caused by a genetic abnormality or a a birth defect in which the spinal column doesn’t close. I suggest to consult a neonatologist in your area and discuss with him the possible causes and the necessary treatement for the baby. Hope this is helpful. Best regards.