What are the chances of a child having spina bifida if there is no history of it on the mother's side of the family, but the father has it? Also, if the father has a mild type that is not physically debilitating, what are the chances that his children could either have the disease or a more serious type that could be debilitating or even paralyzing to the child?
This is a really good question, best answered by a geneticist who can look at your individual situation, but I can give you some basic information. Spina bifida doesn't follow a simple recessive path like blue eyes, but there is a genetic component. Having one parent with spina bifida increases the chances of spina bifida to about 4 percent. This means that the most likely outcome is that your baby will be fine (96 percent chance), but that your baby is at a higher risk than the general population. The severity can be greater or less than the affected relative. Spina bifida is considered multifactorial. This means that other factors, including the physical and biochemical environment during pregnancy, may also affect the odds. The March of Dimes provides clear, accurate information about spina bifida and related conditions.
Prenatal supplementation with folic acid, a vitamin in the B vitamin family, decreases the likelihood of spina bifida. Folic acid works best if the mom takes it starting a few months before pregnancy, since fetal organs form just three to eight weeks after conception. The dose recommendation depends on the level of risk. Women at average risk should take 0.4 milligrams (400 micrograms) of folic acid every day. This can be obtained in a women's multivitamin, a prenatal vitamin, or by just taking folic acid supplements. Moms-to-be who are at increased risk may be advised to take as much as 4 milligrams (10 times the usual dose), but that should only be done under a doctor's supervision, with prescription folic acid supplements. Since moms who are overweight to the point of having a body mass index (BMI) over 30 may also be at increased risk for spina bifida, as are moms who are diabetic (pre-gestational diabetes, not gestational diabetes), getting good medical care, and maintaining a normal body weight can also help prevent spina bifida.
Your doctor or midwife can give you more information. Families at risk for genetic conditions may benefit from consultation with a genetic counselor. The geneticist can look at both family histories, and give you specific information on risk and prevention. To find a genetic counselor near you, ask your doctor or midwife, or contact the National society for Genetic Counselors.