Neural Tube Defects in South Carolina 1992-2019: A Review of Risk Factors

Neural tube defects (NTDs) are one of the most common major birth defects, yet the reasons for occurrence of many NTDs are still not well understood. This study sought to determine the presence of seven specific NTD risk factors in a sample of 515 isolated NTD cases that occurred in South Carolina between 1992 and 2019.

A total of 1351 NTD cases were ascertained in the state between 1992 and 2019 using data from the South Carolina NTD Surveillance and Prevention Program. Medical and pregnancy data were available for 723 of the children, whose mothers chose to enroll in the prevention portion of the program. This study focused on examining the presence of seven NTD risk factors in 515 (71.2%) of these 723 cases in which the NTDs were isolated birth defects and had no identified probable cause, such as a chromosome abnormality.

Of the 515 isolated NTD cases examined in this study, 26.3% had mothers with maternal obesity, 24.0% had exposure to maternal hyperthermia, 7.6% had Hispanic race/ethnicity, 4.7% were the product of a twin or multiple pregnancy, 4.1% had mothers with pregestational diabetes mellitus, and 1.4% had maternal exposure to drugs that affect folate metabolism. In addition, 12.2% of the mothers and 12.1% of the infants were homozygous for the MTHFR C677T variant allele. Of the NTD cases under review, 57.0% had one or more of the risk factors and 15.2% had two or more risk factors.

These findings on NTD risk factors may provide focus areas for continued efforts to reduce preventable NTDs.