Caudal regression syndrome is a rare congenital disorder. It’s estimated that 1 to 2.5 in every 100,000 newborns is born with this condition.

It occurs when the lower spine doesn’t fully form before birth. The lower spine is a part of the “caudal” half. This area contains the parts of the spine and bones that form the hips, legs, tailbone, and several important organs in the lower body.

This condition is sometimes called sacral agenesis because the sacrum, a triangle-shaped bone that connects the backbone to the pelvis, only partially develops or doesn’t develop at all.

Keep reading to learn more about why this may happen, what treatment options are available, and what to expect in the short and long terms.

The exact cause of caudal regression syndrome isn’t always clear. Some research suggests that having diabetes during pregnancy, especially if it isn’t managed, can increase the chance of your child’s caudal region not fully developing.

Since this condition also occurs in infants born to those without diabetes, there may be other genetic and environmental factors involved.

The first signs of caudal regression syndrome usually appear between weeks 4 and 7 of pregnancy. In most cases, the condition can be diagnosed by the end of the first trimester.

If you have diabetes — or if you’ve developed gestational diabetes during pregnancy — your doctor may perform an ultrasound specifically to look for signs of this condition. Otherwise, routine ultrasound tests will look for any fetal abnormalities.

If your doctor suspects caudal regression syndrome, they may perform an MRI after 22 weeks of pregnancy. This will allow them to see even more detailed images of the lower body. An MRI may also be used after birth to confirm the diagnosis.

After a diagnosis is made, your doctor will use ultrasound or MRI testing to determine how severe the condition is.

Your child’s symptoms will depend on the type of caudal regression syndrome that’s diagnosed.

Mild cases may not cause any noticeable changes in your child’s appearance. But in severe cases, your child may have visible differences in the leg and hip area. For example, their legs may be permanently bent in a “frog-like” stance.

Other visible characteristics may include:

  • spine curving (scoliosis)
  • flat buttocks that are noticeably dimpled
  • feet bent upward at a sharp angle (calcaneovalgus)
  • clubfoot
  • imperforate anus
  • opening of the penis on the underside instead of the tip (hypospadias)
  • testicles not descending
  • not having any genitals (genital agenesis)

Your child may also experience the following internal complications:

  • abnormally developed or missing kidneys (renal agenesis)
  • kidneys that have grown together (horseshoe kidney)
  • nerve damage to the bladder (neurogenic bladder)
  • bladder that sits outside of the abdomen (bladder exstrophy)
  • misshapen large intestine or large intestine that sits abnormally in the gut
  • intestine that pushes through weak areas of the groin (inguinal hernia)
  • vagina and rectum that are connected

These characteristics can lead to symptoms such as:

Treatment depends on how severe your child’s symptoms are.

In some cases, your child may need special shoes, leg braces, or crutches to help them walk and move around. Physical therapy may also help your child build strength in their lower body and gain control of their movements.

If your child’s legs didn’t develop, they may be able to walk using artificial, or prosthetic, legs.

If your child has trouble controlling their bladder, they may need a catheter to drain urine. If your child has an imperforate anus, they may need surgery to open a hole in their intestine and pass stools outside of their body into a bag.

Surgery can also be done to treat certain symptoms, such as bladder exstrophy and inguinal hernia. Surgery performed to treat these symptoms usually resolves them completely.

Your child’s outlook will depend on the severity of their symptoms. Their doctor is your best resource for information about your child’s individual diagnosis and any anticipated complications.

In mild cases, your child may go on to live an active and healthy life. Over time, they may be able to use special shoes, braces, or prosthetics to support their body weight and help them move around.

In severe cases, complications in the heart, digestive system, or renal system may affect your child’s life expectancy. Your doctor can provide you with more information about what to expect after childbirth and discuss your options moving forward.