Hello! Happy New Year as well!
To answer your question, after researching on this particular subject, there is still no conclusive answer as to why cranial neurulation defects are more common in females. However, besides the two hypotheses we have mentioned in the report, a more recent one from a study by Liu et al. (2018) states that it could be caused by a disproportionate effect of folic acid (FA) which alters the sex-specific prevalence of neural tube defects (NTDs). Folic acid is an important periconceptional supplement which dramatically reduces the risk for NTDs in offspring. In the splotch mouse strain, dietary folate deficiency exacerbates female susceptibility to exencephaly. If such case is the same in some human NTDs, it is expected that an increase in population-level folate status may have a greater effect on NTDs in women than in men. This is consistent with the findings of Liu et al. (2018) after they implemented a massive FA supplementation programme, where the prevalence of NTDs decreased to a greater degree in women than in men.
Liu, J., Xie, J., Li, Z., Greene, N., & Ren, A. (2018). Sex Differences in the Prevalence of Neural Tube Defects and Preventive Effects of Folic Acid (FA) Supplementation among Five Counties in Northern China: Results from a Population Based Birth Defect Surveillance Programme. BMJ Open. doi:10.1136/bmjopen-2018-022565
To answer your question, after researching on this particular subject, there is still no conclusive answer as to why cranial neurulation defects are more common in females. However, besides the two hypotheses we have mentioned in the report, a more recent one from a study by Liu et al. (2018) states that it could be caused by a disproportionate effect of folic acid (FA) which alters the sex-specific prevalence of neural tube defects (NTDs). Folic acid is an important periconceptional supplement which dramatically reduces the risk for NTDs in offspring. In the splotch mouse strain, dietary folate deficiency exacerbates female susceptibility to exencephaly. If such case is the same in some human NTDs, it is expected that an increase in population-level folate status may have a greater effect on NTDs in women than in men. This is consistent with the findings of Liu et al. (2018) after they implemented a massive FA supplementation programme, where the prevalence of NTDs decreased to a greater degree in women than in men.
Liu, J., Xie, J., Li, Z., Greene, N., & Ren, A. (2018). Sex Differences in the Prevalence of Neural Tube Defects and Preventive Effects of Folic Acid (FA) Supplementation among Five Counties in Northern China: Results from a Population Based Birth Defect Surveillance Programme. BMJ Open. doi:10.1136/bmjopen-2018-022565