Potter Syndrome (hereinafter "PS") is a term to describe a common physical appearance of infants born after being in the womb with oligohydramnios (dramatically decreased amniotic fluid volume). Oligohydramnios is, in cases of PS, observed secondary to renal diseases such as bilateral renal agenesis (BRA). BRA is often referred to as Classic Potter sequence. BRA means complete absence of kidneys and often accompanies complete absence of ureters. BRA has been estimated to occur at a frequency of approximately 1:4000 to 1:8000 fetuses and neonates but may occur at a greater frequency. PS is twice as common in males as females.
BRA appears to have a predominantly genetic etiology. There are several genetic pathways that could result in this condition. To date, few of these pathways or candidate genes have been considered or analyzed regarding BRA. Basically, there are few answers, if any, as to why and how BRA occurs and whether it will recur. Recurrence rates are often cited as 3-5%.
PS is fatal because fetal kidneys produce urine and that urine compromises most of the amniotic fluid in the 2nd and 3rd trimesters of pregnancy. The fetal urine is also critical to the proper development of the lungs by helping to expand the airways and supplying Proline, a critical amino acid to the lungs. Alveoli are the small sacs in the lungs that exchange oxygen with the blood. If the alveoli, and thereby the lungs, are underdeveloped at the time of birth the infant will not be able to breathe air properly and will go into respiratory distress shortly after birth due to pulmonary hypoplasia (underdeveloped lungs). The fetal urine also cushions the fetus from being compressed by the mothers’ uterus as it grows.
Babies born with Potter's Syndrome may be stillborn or may survive anywhere from minutes to precious hours after birth.
*Information obtained from wikipedia and kidneygenes.com
Writer's layman explanation: Basically, a baby with Potter's has no or underdeveloped/cystic kidneys which do not function properly if at all and this causes an absence of amniotic fluid which is required to mature the baby's lungs.