At 8 weeks pregnant, your baby measures about 1.6 centimeters (roughly 0.6 inches) from crown to rump and weighs approximately 1 gram, or 0.04 ounces. That’s about the size of a raspberry. Despite being tiny enough to sit on your fingertip, your baby is in the middle of a massive developmental sprint, with all major organs and body systems already taking shape.
Size Comparisons That Actually Help
Crown-rump length is the standard measurement at this stage, taken from the top of the head to the bottom of the torso since the legs are too small and curled to measure reliably. At 8 weeks, that length falls around 14 to 16 millimeters. To picture it, think of a kidney bean or a single raspberry. Your baby has roughly doubled in size from just a week ago, and will nearly double again over the next two weeks.
Weight at this point is almost negligible. At about 1 gram, your baby weighs less than a paperclip. Significant weight gain doesn’t really begin until the second trimester, when organs mature and fat stores start to develop.
What Your Baby Looks Like Right Now
Eight weeks marks a turning point in appearance. Your baby is starting to look less like a cluster of cells and more like a tiny human. The head is still disproportionately large compared to the body, making up nearly half the total length, because the brain is growing rapidly. Small indentations on either side of the head are forming into ears, and the eyes, still covered by skin that will become eyelids, are visible as dark spots.
The limbs are developing quickly. Leg buds have taken on a paddle-like shape, and fingers have begun to form on the hands, though they’re still webbed together. Those webbed digits won’t separate into individual fingers and toes until around week 10. A tiny tail-like structure that was visible in earlier weeks is nearly gone.
Organs Forming at 8 Weeks
This is one of the most critical periods of the entire pregnancy. By week 8, all of the major organs and body systems are actively developing. The heart has been beating since around week 5 or 6 and now has four distinct chambers. The liver, lungs, and kidneys are all present in early form. The digestive tract is taking shape, and the neural tube (the precursor to the brain and spinal cord) has closed.
Because so much organ formation is happening simultaneously, the period from roughly weeks 3 through 8 is called the embryonic period, and it’s when your baby is most sensitive to anything that could disrupt development. After this window, the basic architecture of every major organ is in place, and the remaining months focus on growth and refinement.
Embryo vs. Fetus: The Transition
At 8 weeks, your baby is still technically classified as an embryo. The shift from “embryo” to “fetus” happens at the end of the 10th week of pregnancy, which corresponds to about 9 weeks after fertilization. This isn’t just a naming convention. It reflects a real biological milestone: by that point, the foundational structures of all organs are established, and your baby enters a phase of rapid growth rather than initial formation.
What You’ll See on an Ultrasound
If you have an ultrasound around 8 weeks, it will typically be transvaginal rather than abdominal, since your baby is still too small to image clearly through the abdomen. On screen, you’ll likely see the gestational sac, the yolk sac (a small round structure that provides nutrients until the placenta takes over), and your baby as a small, bright shape with a flickering heartbeat.
The yolk sac is visible from about week 5 and continues to grow through week 10 before gradually disappearing. At 8 weeks, a provider can usually measure the crown-rump length to confirm your due date, since this measurement is one of the most accurate ways to date a pregnancy in the first trimester. The heartbeat, often between 150 and 170 beats per minute at this stage, is typically the most reassuring thing on the screen.
Changes in Your Body
You likely aren’t showing yet, but things are shifting internally. Your uterus has already grown from roughly the size of a small pear to the size of a tennis ball. That growth can create a feeling of fullness or mild cramping in your lower abdomen even though there’s nothing visible from the outside. Increased blood volume, rising hormone levels, and the energy demands of building a placenta contribute to the fatigue, nausea, and breast tenderness that tend to peak between weeks 8 and 12.
Your baby may be smaller than a grape, but the biological investment your body is making is enormous. By the end of this week, the heaviest lifting of organ formation is nearly complete, setting the stage for the rapid growth that defines the rest of pregnancy.