The 9-week ultrasound is an early-pregnancy procedure often referred to as a “viability scan” because it confirms the healthy progression of the pregnancy. This check-up provides the first visual confirmation of the developing embryo and gives medical providers important baseline information. Patients frequently have questions about what to expect regarding the specific method used.
Determining the Method Used at 9 Weeks
The most common method for a 9-week ultrasound is the transvaginal approach, which is considered an internal scan. This preference is due to the small size of the gestational sac and the embryo, which is typically only about one inch long. Since the uterus is still situated low within the pelvis, visualization through the abdomen is challenging.
The transvaginal probe is inserted gently into the vaginal canal, which allows the ultrasound device to be positioned much closer to the uterus. This proximity produces significantly higher-resolution images and allows for more precise measurements of the tiny structures. An external, or transabdominal, ultrasound may be attempted first, but factors like bowel gas or the patient’s body composition can often obscure the view, necessitating the switch to the internal method for accurate data collection.
Preparing for the Ultrasound Appointment
Preparation for the internal scan focuses mainly on comfort and clear imaging. Unlike external ultrasounds performed later in pregnancy, which require a full bladder to push the uterus up, the transvaginal method typically requires an empty bladder. This distinction is important for both patient comfort and optimal image quality, as an empty bladder improves the clarity of nearby structures.
Patients are positioned on their back, similar to a pelvic examination, sometimes with their feet in stirrups. The procedure involves the use of a sterile, lubricated wand, which is gently inserted into the vagina. The wand is designed to be narrower than a speculum used for a Pap smear, and the process is usually quick, often lasting only five to ten minutes. While some slight pressure or discomfort may be felt from the movement of the probe, the procedure should not be painful.
What the Scan Confirms
The nine-week scan is highly significant because it provides several pieces of foundational medical data that guide the remainder of prenatal care.
- Confirmation of viability: This is achieved by detecting a fetal heartbeat. Once the embryo’s Crown-Rump Length (CRL) measures more than seven millimeters, cardiac activity should be easily visible on the scan.
- Accurate dating of the pregnancy: The Crown-Rump Length (CRL) measurement is used to establish gestational age. The fetal growth rate is highly standardized during this early phase, making the 9-week CRL measurement the most accurate method for calculating the estimated due date, often with an accuracy within three to five days.
- Location confirmation: The scan confirms that the pregnancy is intrauterine, meaning the gestational sac is properly implanted inside the uterus, which rules out an ectopic pregnancy.
- The number of gestational sacs: The scan confirms the number of gestational sacs, indicating whether the patient is carrying a single embryo or multiples.