Final answer:
Subarachnoid hemorrhage is the condition where you would not expect to find an elevated alpha-fetoprotein level during a routine screen at 16 weeks gestation, unlike neural tube defects such as encephalocele, myelomeningocele, and spina bifida.
Step-by-step explanation:
The condition in which you would not expect to find an elevated alpha-fetoprotein level during a routine screen at 16 weeks gestation is D) Subarachnoid hemorrhage. Elevated levels of alpha-fetoprotein are typically associated with neural tube defects (spina bifida), which include encephalocele, myelomeningocele, and spina bifida. These defects occur when the neural tube does not fully close during early fetal development, potentially leading to the protrusion of meninges and neural tissue through the vertebral column. Subarachnoid hemorrhage, on the other hand, is a condition where bleeding occurs between the brain and the surrounding layer of tissue, not typically associated with elevated alpha-fetoprotein levels during gestation.