I have searched for information on your question, and I found several places where people speak about spina bifida. As far as I see, researchers are still working on the genetics behind spina bifida. I could not find any statistics that show differences between the amount of boys and girls having Spina Bifida, but a article mentions that spina bifida are essentially identical in boys and girls.

Here is the information that might help you in your project:

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Anyone can have a baby with spina bifida. However, couples who have already had a baby with spina bifida or another NTD (neural tube defects) have an increased risk of having another affected baby. A couple with one child with spina bifida usually has about a 4 percent chance, and a couple with two affected children has about a 10 percent chance, of having another affected baby. Similarly, when one parent has spina bifida, there is about a 4 percent chance of passing the disorder on to the baby. Couples who have had an affected baby or have a family history of NTDs (neural tube defects) should consult a genetic counselor to discuss risks to their future children.

In most cases, spina bifida occurs by itself. However, sometimes spina bifida occurs as part of a syndrome with other birth defects. In these cases, recurrence risks in another pregnancy may vary widely.

Spina bifida and other NTDs (neural tube defects) occur more commonly in some ethnic groups than others. For example, NTDs (neural tube defects) are more common in Hispanics and Caucasians, and less common among Ashkenazi Jews, most Asian ethnic groups and African-Americans.

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Ninety-five percent of people with spina bifida have no family history of the condition. While there is no guaranteed method to prevent birth defects, studies show that when a woman takes folic acid prior to her pregnancy and through the first semester, the chance of a baby developing spina bifida is reduced by up to 70 percent.

It is recommended that all women of childbearing age consume 0.4 milligrams (400 micrograms) of folic acid each day. Women who have already had a pregnancy with spina bifida are advised to take an even larger dose of folic acid they should take 4.0 milligrams every day. However, even with a daily dose of folic acid, a woman can still have a baby with spina bifida. Factors that Increase the Chance of a Pregnancy with Spina BifidaGenetics, environmental factors, certain illnesses, medications and other factors affect the outcome of a pregnancy, including:

Previous pregnancy with spina bifida
Family history of spina bifida
Maternal insulin-dependent diabetes
Maternal use of certain anti-seizure medications
Medically diagnosed obesity in the mother
Race/ethnicity
Exposure to high temperatures in early pregnancy
Paternal exposure to Agent Orange