Typically, blood is drawn or urine is collected in order to check hCG levels when a pregnancy is suspected. This hormone test provides a firm diagnosis of pregnancy and can be used to monitor the health of the fetus during the first few weeks of a pregnancy. The hCG level generally doubles every 72 hours, reaching its peak in the first eight to eleven weeks of the pregnancy and then declining and leveling off for the remaining gestation period.
When doubling does not occur, or if levels are excessively high or low at any given point, there is cause for further investigation. If the repeated hormone test shows that levels have not doubled, it may indicate an unviable pregnancy. If levels are too low or too high, it may mean that the estimated time of conception is incorrect or that multiple gestations may be present. There are many variations in these hormone levels and it is important to seek the advice of an obstetrician to guide you, especially in these critical early stages of pregnancy.
Other tests may be ordered throughout pregnancy to manage the ongoing health of the mother and the fetus. Several common tests include ultrasound, an AFP blood test and screening, and a glucose tolerance test.
The alpha-fetoprotein, or AFP, blood test checks the levels of AFP in the pregnant woman's blood. AFP is produced by the fetal liver and the levels in the woman's blood can determine the risk of problems, such as spina bifida or anencephaly. It is part of the maternal serum triple or quadruple screening test for chromosomal issues, such as Down syndrome or Edwards syndrome. The levels seen in the AFP screening determine the risk category that a fetus falls into for these congenital abnormalities. In addition to AFP levels, hCG and estrogen levels are also checked to better inform the evaluation of risk.
These tests are simply a screening, which means that once a risk factor is determined it is the mother's choice to move forward with more definitive testing, such as undergoing amniocentesis. Certain measurements on fetal ultrasound, such as the nuchal fold thickness and femur length during the first and second trimesters, are also factors that affect furthering diagnostic testing.
As with all tests throughout pregnancy, results are best interpreted through your obstetrician and a coordinated plan of care should be established.