At 8 weeks pregnant, your baby is roughly the size of a raspberry, measuring about 14 to 18 millimeters from crown to rump (just over half an inch). It still looks more like a tiny tadpole than a newborn, but this week marks a turning point: nearly all the major organs and body systems are forming, and the overall shape is starting to look distinctly human.
Size and Overall Shape
Your baby is small enough to sit on the tip of your finger. The head is still disproportionately large compared to the rest of the body, making up almost half of the total length. That oversized head reflects how rapidly the brain is growing right now. The body has a curved, C-shaped posture, and the small tail-like structure that was visible in earlier weeks is disappearing. By the end of week 8, it will be gone entirely.
Face and Head
Facial features are just beginning to take shape, though they’re far from recognizable. The eyes appear as dark spots on either side of the head, and thin folds of skin are starting to form what will eventually become eyelids. The tip of the nose and the upper lip are emerging. Small indentations on the sides of the head mark where the outer ears will develop. Everything is still very rudimentary, but the basic blueprint of your baby’s face is being laid down this week.
Arms, Legs, and Fingers
The leg buds have taken on a paddle-like shape, and fingers have begun to form on the hands. At this stage, the fingers are still partially webbed, with thin tissue connecting them. Over the next couple of weeks, that webbing will gradually disappear as individual digits separate. The arms are slightly more developed than the legs (arms consistently lead legs by a few days throughout early development), and tiny elbows are starting to bend. Toes are forming too, but they’re a bit behind the fingers in development.
Heart and Internal Organs
The cluster of cells that forms the heart has been pulsing since around week 5, beating roughly 110 times per minute. By week 8, that rate has increased to about 150 to 170 beats per minute, nearly twice the speed of your own heart. All of the major organs and body systems are actively developing. The brain is forming distinct sections and nerve cells are branching out rapidly. The digestive tract is taking shape, and the liver, kidneys, and lungs are in their earliest stages. None of these organs are functional yet, but the structural groundwork is being built this week.
Movement You Can’t Feel Yet
Your baby is already making small, spontaneous movements. These are subtle, involuntary twitches as the muscles and nervous system begin to connect. You won’t feel any of this for months. Most people don’t notice movement until somewhere between 16 and 22 weeks. But if you happen to have an ultrasound at 8 weeks, you might catch a tiny flicker of motion on the screen.
What You’d See on an Ultrasound
An 8-week ultrasound (usually done transvaginally at this stage for a clearer image) shows several landmarks. The gestational sac, which has been visible since about 5 weeks, surrounds the embryo. Inside it, you’ll see the yolk sac, a small round structure that provides nutrients before the placenta takes over. The embryo itself appears as a small, bright shape with a visible flicker of cardiac activity.
At this point, your baby is measurable on ultrasound, and your provider will likely take a crown-to-rump length measurement to confirm your due date. The amnion, the thin membrane that will become the amniotic sac, is also visible by now. Don’t expect to make out arms or a face on the screen. At this size, the embryo looks like a small bean with a flickering dot where the heart is working.
Embryo vs. Fetus: The Transition
Your baby is still technically classified as an embryo at 8 weeks. According to ACOG, the shift from “embryo” to “fetus” happens after 8 weeks post-fertilization, which corresponds to about 10 weeks of pregnancy (since pregnancy is dated from your last menstrual period, not conception). The distinction isn’t just a label change. The embryonic period is when all the major structures form from scratch. Once the fetal period begins, those structures grow and mature, but the foundational building is largely complete. Week 8 is the final stretch of that critical construction phase.