At 8 weeks pregnant, your baby is roughly 16 to 22 millimeters long, or about half an inch to just under an inch. That’s close to the size of a raspberry or a kidney bean. At this stage, weight is so minimal it’s measured in fractions of a gram, typically around 1 gram or less.
How Size Is Measured at 8 Weeks
Doctors measure early pregnancy size using something called crown-rump length (CRL), which is the distance from the top of the head to the bottom of the torso. Legs aren’t included because the embryo is curled up tightly at this point. A CRL of about 16 mm corresponds to 8 weeks and 1 day, while 22 mm lines up closer to 8 weeks and 6 days. So even within a single week, your baby nearly doubles in length. This measurement is one of the most accurate ways to date a pregnancy in the first trimester.
What’s Developing at 8 Weeks
Despite being smaller than a grape, your baby already has a lot going on. All of the major organs and body systems are actively forming. The heart has been beating for a couple of weeks by now and has divided into its four chambers. The hands and feet exist but still look webbed, almost paddle-like. Fingers are just starting to separate.
Facial features are coming together quickly. The eyes become visible, the upper lip and nose have formed, and small swellings that will eventually shape the outer ears are appearing. The trunk and neck are beginning to straighten out, giving the embryo a slightly more human-looking profile than even a week before. One quirky detail: most embryos grow a small tail early in development, and by 8 weeks it has typically disappeared, absorbed into what becomes the tailbone.
The umbilical cord is also fully developed at this point, actively delivering oxygen and nutrients from the placenta to the embryo.
What You’d See on an Ultrasound
If you have an ultrasound around 8 weeks, don’t expect to see anything that looks like a baby yet. On screen, your baby will resemble a small oblong bean inside a dark, fluid-filled space called the gestational sac. You’ll also likely see the yolk sac, which appears as a small bubble-like structure that helps nourish the embryo until the placenta fully takes over.
The technician will look for a few key things: the gestational sac, the fetal pole (the earliest visible form of the embryo), and a heartbeat. Depending on the equipment and your provider’s setup, you may actually get to hear the heartbeat during this visit. At 8 weeks, the heart rate is typically between 150 and 170 beats per minute, roughly twice as fast as yours.
What’s Changing in Your Body
Your baby is tiny, but your uterus is already adjusting. By week 8, it has grown to about the size of a tennis ball, up from its usual size of roughly a small pear. It’s still tucked behind your pelvic bone, so most people aren’t showing yet. That said, you may notice your waistband feels tighter, bloating is common, and symptoms like nausea, breast tenderness, and fatigue tend to peak right around this time as hormone levels climb steeply.
How 8 Weeks Compares to Nearby Weeks
Growth in the first trimester is exponential. At 7 weeks, the embryo is roughly 10 mm. By 8 weeks it’s around 16 to 22 mm. By 9 weeks it will reach about 23 to 30 mm. To put it another way, your baby roughly triples in length between weeks 7 and 9. This period also marks a major transition: at the end of week 8, the embryonic stage officially ends and the fetal stage begins. From this point forward, the focus shifts from forming new organs to growing and refining the ones already in place.