Is AFP accurate with twin pregnancies?
I am expecting twins and my doctor told me that an alpha fetoprotein test is not relevant because there are no norms for twins. Is this true?Question:
The difficulty with twins or any multiple gestation is interpretation of abnormal levels due to "discordance". That means how do we interpret one reading for both. If one twin has a neural tube defect and the other one does not, how would that change the value and by how much?
Maternal alpha fetoprotein testing detects about 65 percent of all twin pregnancies. The median value for twins is approximately 2.5 multiples of the median. Most providers will do further testing and ultrasound for any value of 1.5 multiples of the median. Upper limit of 4.5 multiples of the median is used as a cut off for normal. The test must be done between 15 and 20 weeks and the lab does have appropriate levels for each week of gestation and maternal weight.
I would recommend that you find out the lab where the AFP was sent and call them for their norms for twins.Answer: