Type I is due to autosomal recessive polycystic kidney disease (ARPKD), which occurs at a frequency of approximately one in 16,000 infants. The kidneys of the fetus/neonate will be enlarged, have many small cysts filled with fluid and will fail to produce an adequate volume of fetal urine. The liver and pancreas of the fetus may also show fibrosis and/or a cystic change.
In recorded medical and research history BRA has proved to be 100% lethal in all cases of singleton births. Various other forms of the syndrome are, or are near, 100% lethal.