Spina bifida is officially classified as a rare disease in the United States. About 1,278 babies are born with it each year, or roughly 1 in every 2,875 births. An estimated 124,150 people in the U.S. were living with the condition as of 2020, well under the 200,000-person threshold the federal government uses to define a rare disease.
But that straightforward answer comes with an important caveat. The term “spina bifida” covers a spectrum of conditions, and the mildest form is surprisingly common. Whether spina bifida counts as rare depends entirely on which type you’re talking about.
The Mildest Form Is Not Rare at All
Spina bifida occulta, the least severe type, occurs when one or more vertebrae don’t fully close but the spinal cord itself is unaffected. The National Institute of Neurological Disorders and Stroke estimates that 10 to 20 percent of the general population has this condition. Most people with spina bifida occulta never know they have it. It typically causes no symptoms and is often discovered incidentally on an X-ray taken for an unrelated reason.
Because it so rarely causes problems, spina bifida occulta isn’t included in the birth prevalence statistics you’ll see from the CDC. When doctors, researchers, and public health agencies say “spina bifida,” they’re usually referring to the more serious open forms of the condition.
Open Spina Bifida: The Numbers
The forms that do cause significant health effects are meningocele and myelomeningocele. In meningocele, the protective membranes around the spinal cord push through the gap in the spine but the cord itself stays in place. In myelomeningocele, the spinal cord and nerves protrude through the opening. Myelomeningocele is the most serious type and the one most people picture when they hear “spina bifida.” It can cause partial or complete paralysis below the affected area, bladder and bowel problems, and fluid buildup in the brain.
Together, these open forms occur at a rate of about 3 per 10,000 live births in the U.S. That rate varies by ethnicity. Hispanic families see the highest prevalence at 3.80 per 10,000 births, followed by non-Hispanic white families at 3.09 and non-Hispanic Black families at 2.73.
Who Is Living With Spina Bifida Today
A 2020 population estimate found approximately 124,150 people in the U.S. living with spina bifida, ranging from newborns to adults in their 80s. About two-thirds were adults over 30, reflecting decades of improvements in surgical care and management that have dramatically extended life expectancy. Women are affected slightly more often than men, with roughly 67,700 females and 56,500 males in the estimate.
That total of 124,150 falls below the 200,000-person cutoff established by the Orphan Drug Act, which is the legal standard for rare disease status in the U.S. This designation matters because it unlocks research funding and incentives for pharmaceutical companies to develop treatments.
Rates Have Dropped Since the 1990s
Spina bifida is rarer today than it was a generation ago, largely because of folic acid. In the late 1990s, the U.S. and Canada began requiring that folic acid be added to enriched grain products like bread, pasta, and cereal. Folic acid is the synthetic form of folate, a B vitamin that plays a critical role in how the neural tube (the structure that becomes the brain and spinal cord) forms during the first weeks of pregnancy.
Globally, mandatory fortification programs prevented an estimated 22 percent of potential spina bifida and related neural tube defect cases as of 2019. The impact was most dramatic in regions where baseline rates were highest. In parts of eastern Canada, for instance, rates dropped by as much as 38 cases per 10,000 births after fortification began.
Taking a folic acid supplement before and during early pregnancy reduces risk further. Because the neural tube closes within the first 28 days after conception, often before a person knows they’re pregnant, health agencies recommend that anyone who could become pregnant take 400 micrograms of folic acid daily.
Most Cases Are Detected Before Birth
Routine prenatal ultrasound catches the vast majority of open spina bifida cases. In countries with established screening programs, around 88 to 93 percent of cases are identified before birth. Most are found during the second-trimester anatomy scan, typically performed between 18 and 22 weeks of pregnancy, though some are detected as early as the first trimester.
Early detection gives families time to plan. Some cases can be treated with fetal surgery while the baby is still in the womb, which has been shown to improve outcomes compared to repair after birth. In other cases, knowing the diagnosis in advance allows the medical team to prepare for delivery and immediate postnatal care.