According to UpToDate (and other cards in the AnKing), abdominal wall defects are also sources of elevated AFP
1. article title: Omphalocele: Prenatal diagnosis and pregnancy management
article link: https://www.uptodate.com/contents/omphalocele-prenatal-diagnosis-and-pregnancy-management?search=abdominal%20wall%20defects&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#
"Associated maternal findings — The mother is asymptomatic. If a maternal serum alpha-fetoprotein concentration has been performed as part of screening for neural tube defects, it may be elevated"
2. article title: Gastroschisis
article link: https://www.uptodate.com/contents/gastroschisis?search=abdominal%20wall%20defects&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2#H1276141117
"Maternal serum alpha-fetoprotein (MSAFP) is elevated in virtually all pregnancies with gastroschisis."