There are four levels (or "types") of malformation. The least severe indicates partial deformation (unilateral) of the sacrum. The second level indicates a bilateral (uniform) deformation. The most severe types involve a total absence of the sacrum.

Depending on the type of sacral agenesis, bowel or urinary bladder deficiencies may be present. A permanent colostomy may be necessary in the case of imperforate anus. Incontinence may also require some type of continence control system (e.g., self-catheterization) be utilized. Occasionally if deformities of the knees, legs or feet would prove unresponsive to corrective action, amputation at the knee may be proposed.

Before more comprehensive medical treatment was available, full amputation of the legs at the hip was often performed. More recently, the 'amputation' (actually a disarticulation because no cutting of the bone is involved) is done at the knee for those who have bent knee positions and webbing between thigh and calf to enable more ease of mobility and better seating. Some children with knee disarticulation use prosthetic legs to walk. Prosthetics for children without substantial hip and trunk control is usually abandoned in favor of faster and easier wheelchair mobility as the child's weight and age increases. Children may 'walk' on their hands and generally are able to climb and move about to accomplish whatever they need and want to accomplish. Children more mildly affected may have normal gait and no need for assistive devices for walking. Others may walk with bracing or crutches.

There is typically no cognitive impairment associated with this disability. Adults with this disability live independently, attend college, and have careers in various fields. In 2012, Spencer West, a man with sacral agenesis and both legs amputated, climbed Mt. Kilimanjaro using only his hands.

Only a few individuals who did not have fatal kidney and bladder complications are known to have survived beyond birth with this condition.

The outcome of Potter's Sequence is poor. A series of 23 patients in 2007 recorded 7 deaths, 4 in the neonatal period. All 16 survivors have chronic kidney disease, with half developing end stage renal failure (median age 0.3 years, range 2 days to 8.3 years). Survivors had growth impairment (44%) and cognitive and motor development delay (25%)

The first child to survive Bilateral Renal Agenesis (BRA), Abigail Rose Herrera Beutler, was born on July 2013 to US Congresswoman Jaime Herrera Beutler.

A few weeks before she was born, Dr. Jessica Bienstock, a professor of maternal-fetal medicine at Johns Hopkins Hospital, administered a series of saline solution injections into the mother's womb to help the baby's lungs to develop. After Abigail was born, the procedure was considered a success. The infant did not need artificial respiration and could breathe on her own. Her parents kept her on kidney dialysis at home until old enough for a kidney transplant. On February 8, 2016, at the age of two, Abigail received a kidney from her father at the Lucile Packard Children's Hospital Stanford in California.

Ectromelia is a congenital condition where long bones are missing or underdeveloped.

Examples include:

- Amelia

- Hemimelia

- Phocomelia

- Sirenomelia

Caudal regression syndrome or sacral agenesis (or hypoplasia of the sacrum) is a congenital disorder in which there is abnormal fetal development of the lower spine—the caudal partition of the spine.

It occurs at a rate of approximately one per 25,000 live births.

Sirenomelia, alternatively known as Mermaid syndrome, is a rare congenital deformity in which the legs are fused together, giving them the appearance of a mermaid's tail as the nickname suggests.

This condition is found in approximately one out of every 100,000 live births (about as rare as conjoined twins) and is usually fatal within a day or two of birth because of complications associated with abnormal kidney and urinary bladder development and function. More than half the cases of sirenomelia result in stillbirth and this condition is 100 times more likely to occur in identical twins than in single births or fraternal twins. It results from a failure of normal vascular supply from the lower aorta in utero. Maternal diabetes has been associated with caudal regression syndrome and sirenomelia, although a few sources question this association.

VACTERL-H is an expanded form of the VACTERL association that concludes that this diagnosis is a less severe form of sirenomelia. The disorder was formerly thought to be an extreme case of caudal regression syndrome; however, it was reclassified to be considered a separate condition.

Potter sequence is the atypical physical appearance of a baby due to oligohydramnios experienced when in the uterus. It includes clubbed feet, pulmonary hypoplasia and cranial anomalies related to the oligohydramnios. Oligohydramnios is the decrease in amniotic fluid volume sufficient to cause deformations in morphogenesis of the baby.

Oligohydramnios is the cause of Potter sequence but there are many things that can lead to oligohydramnios. It can be caused by renal diseases such as bilateral renal agenesis (BRA), atresia of the ureter or urethra causing obstruction of the urinary tract, polycystic or multicystic kidney diseases, renal hypoplasia, amniotic rupture, toxemia, or uteroplacental insufficiency from maternal hypertension.

The term "Potter sequence" was initially intended to only refer to cases caused by BRA; however, it is now commonly used by many clinicians and researchers to refer to any case that presents with oligohydramnios or anhydramnios regardless of the source of the loss of amniotic fluid.