The journey following a Frozen Embryo Transfer (FET) culminates in the first visualization of the pregnancy. An ultrasound uses high-frequency sound waves to create images of the developing embryo, offering a non-invasive way to assess its progress. This initial scan shifts the focus from the hormonal confirmation of pregnancy to its visual confirmation. Understanding the sequence of events after a successful FET helps manage the wait for this first look.
Confirming Pregnancy with the Beta HCG Test
The first official confirmation of pregnancy after an FET comes from a blood test measuring Human Chorionic Gonadotropin (HCG). This test, often called the Beta HCG or “beta” test, is typically scheduled between 9 and 14 days following the embryo transfer. HCG is produced by the cells that will eventually form the placenta, and its presence is the earliest reliable indicator of implantation.
The initial HCG level provides a baseline, but the trend of the hormone’s concentration is more important for predicting viability. In a healthy early pregnancy, HCG levels are expected to roughly double every 48 to 72 hours. Clinics often repeat this blood test several times to ensure the levels are rising appropriately.
Rising HCG levels are a necessary prerequisite for scheduling the first ultrasound, as they indicate the embryo has implanted and is developing. Once the HCG level reaches a threshold, generally between 1,500 and 2,000 mIU/mL, the pregnancy is typically visible on a transvaginal ultrasound. This hormonal confirmation allows the clinic to transition care toward visual confirmation.
Scheduling the First Viability Ultrasound
The first viability ultrasound is generally scheduled when the pregnancy reaches six to seven weeks gestational age, approximately four to five weeks after the embryo transfer. This timing is calculated based on the transfer date and the age of the transferred embryo (e.g., a five-day blastocyst). The six to seven-week window is chosen because the earliest, most definitive signs of a developing pregnancy should become visible on the scan.
Scanning too early, before six weeks, often yields inconclusive results. For instance, a scan at five weeks might only show the gestational sac, without a visible embryo or heartbeat. This leads to uncertainty and often requires a repeat scan shortly after. Waiting until the six to seven-week mark allows for the visualization of key structures that confirm viability.
For a five-day blastocyst FET, the first scan is usually scheduled two to three weeks after the initial positive HCG blood test. This differs from naturally conceived pregnancies, where gestational age is calculated from the last menstrual period. The fertility clinic provides the exact calculation to ensure the scan captures the developmental milestones.
Key Markers Confirmed During the Scan
The first ultrasound serves as a viability check, with the technician or doctor looking for several specific markers. The first priority is confirming the location of the pregnancy, ensuring it is intrauterine (within the uterus) and ruling out an ectopic pregnancy. A transvaginal ultrasound is often used at this early stage due to its superior image resolution for viewing small pelvic structures.
The scan confirms the presence of the gestational sac (the fluid-filled structure surrounding the embryo) and the yolk sac, which provides early nourishment. The fetal pole, the first visible sign of the developing embryo, should also be clearly visualized. A measurement of the embryo, known as the Crown-Rump Length (CRL), is taken to confirm that the size aligns with the expected gestational age.
The most anticipated finding is the detection of fetal cardiac activity, often called the heartbeat. Electrical impulses in the developing heart tissue can usually be seen around six weeks gestation, and a measurable heart rate is a strong indicator of viability. The scan also allows the medical team to check for the number of fetuses, identifying if the pregnancy is a singleton or a multiple gestation.
Next Steps After a Successful First Scan
Following a successful viability scan, the patient’s care transitions from the specialized fertility clinic to a standard obstetrician or OB/GYN. This process, often called “graduating” from the clinic, typically occurs between seven and ten weeks of pregnancy. The fertility clinic provides the patient’s complete medical records to ensure a seamless handover of care to the new provider.
This transition marks a return to a more standard prenatal schedule, where appointments become less frequent than the intensive monitoring required during the FET cycle. The next major milestone is typically the 12-week prenatal appointment and the first trimester screening ultrasound. This change signifies that the early, high-risk phase of the pregnancy has been successfully navigated.