The 11-week ultrasound marks a significant and highly anticipated milestone, offering the first detailed glimpse into the developing fetus. This scan is typically performed as the first trimester ends, a period when the risk of miscarriage has dropped substantially. It provides a wealth of information regarding the progression of the pregnancy, moving beyond simple confirmation to detailed anatomical and biometric assessment. Seeing the recognizable form of the baby for the first time often creates an immediate and powerful connection for parents.
Size and Scale: How Big Is the Fetus?
At 11 weeks gestation, the fetus is actively growing and is easily measurable on the ultrasound screen. The primary measurement used at this stage is the Crown-Rump Length (CRL), which is the length from the top of the head to the bottom of the buttocks. This measurement is highly accurate for establishing the gestational age and confirming the due date.
The typical size range for a fetus at this point is approximately 4.1 to 5.0 centimeters (1.6 to 2 inches long). The fetus is roughly the size of a small lime or a large fig. Growth is rapid now, as the fetus transitions from the vulnerable embryonic phase into the fetal period, focusing on the maturation of existing structures.
The fetal weight is still minimal, often only a few grams, but the growth rate is accelerating significantly. The CRL measurement is compared to standard growth charts to ensure development is tracking within expected parameters and serves as a foundational data point for monitoring the rest of the pregnancy.
Detailed Visual Features and Observable Movement
The visual transformation from the earlier embryonic stage is dramatic by the 11th week, as the fetus now possesses distinctly human features. The head remains disproportionately large, making up almost half of the total Crown-Rump Length, while the rest of the body begins to lengthen and straighten. This large head proportion is normal and reflects the rapid development of the brain and nervous system.
The face is becoming much more defined, with the profile showing a developing jawline, nose, and distinct ear structures. Tiny fingernails and toenails are beginning to form on the digits, which are now clearly separated. Although the eyelids have formed, they will remain fused shut until much later in the pregnancy.
The 11-week scan often reveals significant movement visible on the screen. The fetus is incredibly active, performing stretches, sudden jerks, and even somersaults within the amniotic fluid. These movements, such as kicking legs or waving arms, are an important sign of a healthy and developing neurological system, even though the mother cannot feel them yet.
Critical Measurements and the Purpose of the Scan
Beyond visual confirmation, the 11-week scan serves several clinical purposes, gathering data that informs the ongoing care plan. A primary assessment involves documenting the fetal heart rate (FHR), which is notably fast at this stage of development. The typical expected range for the FHR at 11 weeks is between 145 and 175 beats per minute.
The sonographer also performs the Nuchal Translucency (NT) measurement, a key component of first-trimester screening. This involves precisely measuring the fluid-filled space at the back of the fetus’s neck (the nuchal fold). An increased measurement can indicate a potential increased risk for certain chromosomal conditions, such as Down syndrome, or for congenital heart defects.
The NT scan is strictly a screening tool, meaning it assesses risk but does not provide a definitive diagnosis. Other measurements taken include confirming the number of fetuses and checking the location and health of maternal structures like the uterus and placenta. This detailed biometric and anatomical information provides a comprehensive check-up and lays the groundwork for monitoring the remainder of the pregnancy.