At 11 weeks of pregnancy, a fetus measures about 41 to 43 millimeters (roughly 1.6 inches) from the top of the head to the bottom of the torso, and weighs around 7 grams, or a quarter of an ounce. That’s about the size of a fresh fig. Small as that sounds, a tremendous amount of development is already underway.
How Size Is Measured at 11 Weeks
Fetal size this early in pregnancy is measured as “crown-rump length,” the distance from the top of the skull to the base of the torso. Legs aren’t included because they’re still curled tightly against the body and vary too much in position to give a reliable number. On ultrasound, the fetus appears as a distinct human shape at this stage, with a visible head, body, and limbs.
Crown-rump length is one of the most accurate ways to date a pregnancy. When measured before 14 weeks, it pins down gestational age to within five to seven days, according to guidelines from the American College of Obstetricians and Gynecologists. The earlier in the first trimester the measurement is taken, the more precise it is, because fetuses grow at very similar rates during this period regardless of genetics or other factors.
What’s Developing at This Stage
At 11 weeks, facial features are becoming more defined. The eyes have moved closer together toward the front of the face, the ears are nearly in their final position, and the nose and mouth are more distinct. Fingernails and toenails started forming around week 10 and continue to develop. External genitalia are also beginning to take shape, though it’s far too early to see them on an ultrasound.
The diaphragm, the muscle responsible for breathing, is already functional enough that the fetus practices inhaling and exhaling amniotic fluid. This process begins around week 10 and can even produce tiny hiccups visible on ultrasound, though you won’t feel them for months. These early breathing movements are a sign the respiratory system is developing on track.
The heart has been beating for several weeks by now and is pumping at a rapid clip. Between weeks 8 and 12, the fetal heart rate averages 140 to 170 beats per minute, roughly twice the rate of an adult heart. It will slow down slightly as the pregnancy progresses. Your provider can pick up this heartbeat clearly on a Doppler device or ultrasound at this point.
The fetus is also starting to move, though you won’t notice it yet. Spontaneous movements begin around 12 weeks, but the fetus is still so small that most people don’t feel anything until 16 to 25 weeks. First-time mothers tend to notice movement later than those who’ve been pregnant before.
Your Body at 11 Weeks
While the fetus is fig-sized, your uterus is approaching the size of a grapefruit. Around 12 weeks it begins to rise up and out of the pelvis, though at 11 weeks it still fits within it. Some people start to notice a slight lower-belly fullness, but a visible bump this early varies widely depending on body type, muscle tone, and whether this is a first pregnancy. Tight waistbands may feel uncomfortable even if nothing is showing yet.
The 11-Week Ultrasound
If you have an ultrasound around this time, it may be part of a nuchal translucency screening, which is offered between 11 and 13 weeks. This scan measures a small pocket of fluid at the back of the fetus’s neck. The measurement is taken in millimeters, and a larger-than-expected amount of fluid can signal a higher chance of certain chromosomal conditions, including Down syndrome, Edwards syndrome, and Patau syndrome, as well as some congenital heart conditions. The scan also checks for the presence of a nasal bone, another early marker.
A nuchal translucency scan is a screening, not a diagnostic test. It estimates risk rather than giving a definitive answer. If results suggest elevated risk, your provider will discuss follow-up options like cell-free DNA testing or diagnostic procedures such as chorionic villus sampling. Many people who get flagged on a screening go on to have completely typical results on further testing.
How Size Changes Week to Week
Growth during the first trimester is rapid and remarkably consistent from one pregnancy to the next. For context, at 10 weeks the fetus measures roughly 31 millimeters, and by 12 weeks it reaches about 54 millimeters. That means the fetus grows nearly a centimeter per week at this stage. Weight gain accelerates even faster in the coming weeks: by 14 weeks, the fetus will weigh close to 43 grams, more than six times its 11-week weight of 7 grams.
If your measurements come in slightly above or below 42 millimeters, that’s perfectly normal. The five-to-seven-day accuracy window for dating means a fetus measuring a few millimeters off the average could simply be a day or two ahead or behind. Consistent growth over time matters more than any single measurement.