The period following an in vitro fertilization (IVF) embryo transfer culminates in the first pregnancy blood test, commonly called the “beta test.” This test is formally known as the quantitative human chorionic gonadotropin (hCG) blood test. It precisely measures the concentration of hCG, the pregnancy hormone produced by cells that will eventually form the placenta. The initial blood draw determines if the embryo has successfully implanted in the uterine lining.
The Initial Beta Test
The first beta test is typically scheduled between nine and fourteen days following the embryo transfer. This window allows enough time for the developing placenta to produce a detectable amount of the hormone hCG in the maternal bloodstream. The result is reported as a numerical value, measured in milli-international units per milliliter (mIU/mL).
A result less than 5 mIU/mL is generally considered negative for pregnancy. While a result greater than 5 mIU/mL confirms the presence of the hormone, most specialists prefer a level greater than 25 mIU/mL to confidently consider the test positive. This single number only confirms that implantation has occurred and does not confirm a viable, ongoing pregnancy.
Subsequent Testing and Doubling Time
To determine if the pregnancy is progressing normally, multiple beta tests are required over a short period. Most clinics mandate at least two, and often three, sequential blood draws scheduled every 48 to 72 hours after the initial measurement. The trend of the hCG level is significantly more informative than the initial number alone.
The primary concept guiding subsequent testing is the “doubling time” of the hCG level. In a healthy, early pregnancy, the hormone concentration is expected to approximately double every two to three days. This rapid rise reflects the appropriate development and growth of the placental tissue. Observing this doubling pattern across three separate tests provides strong evidence that the embryo is developing as expected.
Understanding the Numerical Results
Interpreting the sequential beta tests involves analyzing both the absolute numerical values and the rate at which they increase. A clear positive result is characterized by a high initial number followed by consistent doubling within the 48-to-72-hour window. For example, an initial reading of 100 mIU/mL that rises to 200–300 mIU/mL two days later suggests a strong probability of a healthy, progressing pregnancy.
A low initial result, such as one just above the 5 mIU/mL threshold, is considered a borderline positive. While these pregnancies can sometimes progress successfully, they warrant heightened monitoring, as a lower starting point can be a consequence of delayed implantation. A slow doubling rate (less than 35% increase over 48 hours) is a marker for potential complications, including a non-viable pregnancy, ectopic pregnancy, or miscarriage.
A result that declines or fails to progress after an initial positive reading often points to a “chemical pregnancy.” This describes a very early pregnancy loss where the embryo implanted just long enough to produce a detectable hCG level before development ceased. Follow-up beta tests show the hormone level decreasing or returning to zero. This numerical data helps the physician distinguish between a viable pregnancy and one requiring further assessment.
What Follows the Beta Phase
Once the sequential beta tests have demonstrated an appropriate and sustained doubling rate, the monitoring transitions from blood work to clinical imaging. Typically, after three or four successful beta measurements, the patient is scheduled for the first transvaginal ultrasound. This initial ultrasound is usually performed around six to seven weeks of gestation.
The purpose of this first imaging session is to confirm the location of the gestational sac within the uterus, ruling out an ectopic pregnancy. Clinicians also look for the presence of a fetal pole and a fetal heartbeat, which is the definitive marker for a viable pregnancy. Once viability is confirmed, continued hCG blood testing ceases. The patient is then discharged from the fertility clinic and transitions to a standard obstetrician around eight to ten weeks of gestation for routine prenatal care.