At 8 weeks pregnant, your baby is about the size of a raspberry, weighing roughly 1 gram (0.04 ounces). That’s lighter than a paperclip. From head to bottom, the embryo measures approximately half an inch, or about 1.6 centimeters. Despite that tiny size, an extraordinary amount of development is already underway.
Size Comparisons That Help
A gram is almost impossible to picture on its own, so fruit comparisons are popular for a reason. At 8 weeks, your baby is comparable to a raspberry or a kidney bean. It would fit comfortably on the tip of your finger. For context, just two weeks earlier at 6 weeks, the embryo was closer to the size of a lentil, so growth is happening quickly even though the numbers still sound small.
Your uterus, meanwhile, has already expanded to about the size of a tennis ball, up from its pre-pregnancy size of roughly a small pear. You likely won’t have a visible bump yet, but you may notice your lower abdomen feels firmer or that your pants fit a little differently.
What’s Forming at 8 Weeks
Week 8 is the final week your baby is technically called an embryo. Starting at week 9 (counted from fertilization), it transitions to being called a fetus. That distinction isn’t just a label change. It marks the point where all major organs and body systems have begun forming, and the focus shifts from building new structures to growing and refining them.
By the end of week 8, the heart has been beating for several weeks and is pumping blood through a developing circulatory system. The umbilical cord is fully formed and actively delivering oxygen and nutrients. Tiny arms and legs are present, though the hands and feet still have a webbed appearance, with individual fingers and toes not yet separated. Eyes are becoming visible as dark spots on the face, and the ears are starting to take shape.
One detail that surprises many people: most embryos grow a small tail early in development, and by 8 weeks it has typically disappeared, absorbed into what will eventually become the tailbone (coccyx). The brain is also developing rapidly at this stage, with early nerve pathways forming that will later control movement and sensation.
What You Can See on an Ultrasound
If you have an ultrasound around 8 weeks, you’ll likely see a small, curved shape with a flickering heartbeat. The head appears disproportionately large compared to the body, which is normal. You probably won’t be able to make out facial features or limbs in much detail, but the heartbeat is usually clearly visible and measurable. At this stage, heart rates typically range from 150 to 170 beats per minute.
Your provider may measure the embryo from the top of the head to the bottom of the torso (called crown-rump length) to confirm your due date. This measurement is one of the most accurate ways to date a pregnancy during the first trimester, since embryos grow at a remarkably consistent rate in these early weeks.
How Growth Accelerates From Here
The pace of growth over the next few weeks is dramatic. At 8 weeks, your baby weighs 1 gram. By 12 weeks, that number jumps to around 14 grams, and the embryo-turned-fetus will be roughly 2 to 3 inches long. The webbing between fingers and toes disappears, facial features become more defined, and the skeletal system begins hardening from soft cartilage into bone.
By the end of the first trimester at 13 weeks, all the organ systems that started forming during weeks 5 through 8 are in place and functioning at a basic level. The second trimester then becomes a period of rapid size increases and fine-tuning, with your baby gaining weight more noticeably each week.
Why the Dating Can Feel Confusing
You might notice that different sources seem to disagree on what “8 weeks” means. That’s because pregnancy is typically counted from the first day of your last menstrual period, which is about two weeks before conception actually occurs. So “8 weeks pregnant” by standard pregnancy dating means the embryo itself is closer to 6 weeks old from the point of fertilization. The size and development milestones described here follow the standard pregnancy dating method, which is what your doctor or midwife uses and what you’ll see on most pregnancy apps and calendars.