Spina bifida (Latin: ""split spine"") is a birth defect where there is incomplete closing of the backbone and membranes around the spinal cord. There are three main types: spina bifida occulta, meningocele, and myelomeningocele. The most common location is the lower back but rarely they may occur in the middle back or neck. Occulta has no or only mild signs. Signs of occulta may include a hairy patch, dimple, dark spot, or swelling on the back at the site of the gap in the spine. Meningocele typically causes mild problems with a sac of fluid present at the gap in the spine. Myelomeningocele, also known as open spina bifida, is the most severe form. Associated problems include poor ability to walk, problems with bladder or bowel control, hydrocephalus, a tethered spinal cord, and latex allergy. Learning problems are relatively uncommon.Spina bifida is believed to be due to a combination of genetic and environmental factors. After having one child with the condition or if a parent has the condition there is a 4% chance the next child will also be affected. Not having enough folate in the diet during pregnancy also plays a significant role. Other risk factors include certain antiseizure medications, obesity, and poorly controlled diabetes. Diagnosis may occur either before or after a child is born. Before birth if a blood test or amniocentesis finds a high level of alpha-fetoprotein (AFP) there is a higher chance of spina bifida. Ultrasound examination may also detect the problem. Medical imaging can confirm the diagnosis after birth. It is a type of neural tube defect with other types including anencephaly and encephalocele.Most cases of spina bifida can be prevented if the mother gets enough folate before and during pregnancy. Adding folic acid to flour has been found to be effective for most women. Open spina bifida can be surgically closed before or after birth. A shunt may be needed in those with hydrocephalus and a tethered spinal cord may be surgically repaired. Devices to help with movement such as crutches or wheelchairs may be useful. Urinary catheterization may also be needed.About 5% of people have spina bifida occulta. Rates of other types of spina bifida vary significantly by country from 0.1 to 5 per 1000 births. On average in developed countries it occurs in about 0.4 per 1000 births. In the United States it affected about 0.7 per 1000 births, and in India about 1.9 per 1000 births. Part of this difference is believed to be due to race with Caucasians at higher risk and partly due to environmental factors.