At nine weeks of pregnancy, a fetus is roughly 22 to 31 millimeters long, measured from head to rump. That’s about the size of a cherry or a grape. The body has a recognizable head, torso, and tiny limb buds that are starting to look more like arms and legs, though the head is still disproportionately large compared to the rest of the body.
Size Through Week Nine
A fetus grows noticeably during the ninth week alone. At the start of week nine, the crown-to-rump length averages about 22 mm (just under an inch). By the end of the week, it reaches approximately 31 mm, meaning it grows nearly a centimeter in seven days. Weight is still too small to measure reliably at this stage, typically estimated at around 2 to 3 grams.
Crown-rump length is the standard measurement used during early pregnancy because the legs are curled tightly against the body, making a full head-to-toe measurement impractical. This curled-up posture is a big part of why early ultrasound images show a rounded, compact shape rather than anything stretched out.
Visible Features at Nine Weeks
Week nine marks the official transition from embryo to fetus, and the body is starting to look distinctly human rather than like a cluster of cells. Arms are growing longer, and elbows have formed, giving the upper limbs a visible bend for the first time. Toes are now visible on the developing feet, though fingers and toes still have webbing between them. That webbing disappears over the following week as the digits separate and lengthen.
Eyelids are forming over the eyes, though they’ll stay fused shut for months. The face is becoming more defined: the nose, mouth, and outer ears are taking shape, and the head is rounding out. A thin layer of skin covers the body, but it’s still translucent.
What’s Happening Inside
All the major internal organs are actively developing at this point. The heart, brain, lungs, kidneys, and gut are in place and growing more complex. The heart has been beating since around week six, and by week nine it’s pumping at roughly 170 beats per minute, nearly twice the rate of an adult heart. This rapid rate is normal for early fetal development and peaks around weeks nine to ten before gradually slowing later in pregnancy.
The liver, which is relatively large at this stage, has begun producing blood cells. Tiny muscles are forming throughout the body, and the fetus may make small, spontaneous movements, though they’re far too slight for you to feel.
External genitalia have not yet differentiated enough to determine biological sex visually. The structures that will eventually become either male or female anatomy are present but look identical at nine weeks. Most providers can’t reliably identify sex on ultrasound until around 18 to 20 weeks.
What You’d See on an Ultrasound
If you have an ultrasound at nine weeks, you’ll be able to see the head, body, and limbs as distinct shapes. Some scans can even pick up the beginnings of fingers and toes, depending on the quality of the equipment and the angle of the image. The overall shape is often described as a “gummy bear” silhouette: a large rounded head, a curved body, and small limb buds extending outward.
You’ll likely also see or hear the heartbeat, which shows up as a rapid flicker on the screen. Because the fetus is still so small, most nine-week ultrasounds are done transvaginally rather than on top of the abdomen, since the internal approach gives a much clearer image at this early stage. The fetus appears bright white against a dark background, surrounded by the gestational sac and the early placenta.
How Week Nine Compares to Nearby Weeks
The difference between week eight and week nine is significant in developmental terms. At eight weeks, the embryo still has a visible tail structure and more paddle-like limbs. By nine weeks, the tail has receded, the limbs have joints, and the overall proportions are shifting toward a more recognizable human form. Over the following two to three weeks, the face will continue to refine, the fingers and toes will fully separate, and the fetus will roughly double in length, reaching about 5 to 6 centimeters by the end of week twelve.