At 7 weeks pregnant, your baby measures about 7 to 8 millimeters from head to rump, roughly one-quarter to one-third of an inch. That’s about the size of a blueberry. While that sounds tiny, it represents rapid growth from just a cluster of cells a few weeks ago, and a lot is happening inside that small frame.
Exact Measurements Through Week 7
Embryo size is measured as “crown-rump length,” which is the distance from the top of the head to the bottom of the torso (legs aren’t included because they’re curled up tight). At the start of week 7, the embryo measures around 7.0 mm. By the end of the week, at 7 weeks and 6 days, it reaches approximately 7.9 mm. That’s nearly a full millimeter of growth in just seven days.
To put it in perspective, the NHS compares a 7-week embryo to a small grape, while most pregnancy resources use a blueberry as the go-to comparison. Either works. The point is that your baby fits comfortably on your fingertip.
What’s Developing at This Size
Despite being smaller than a penny, the embryo at 7 weeks is building the structures that will become arms and legs. The arm buds have started to take on a paddle-like shape, and the lower limb buds that will eventually become legs are just appearing. These won’t look like arms and legs for several more weeks, but the basic blueprint is forming now.
The brain is growing quickly and is disproportionately large compared to the rest of the body. The head makes up a big chunk of the overall length at this stage. Tiny depressions where the nostrils will form are beginning to appear, and the earliest structures of the eyes are developing. The heart, which started beating around week 5 or 6, is pumping blood through a simple but functional circulatory system. Internal organs like the kidneys, liver, and intestines are in their earliest stages of formation, though none are fully functional yet.
What You’d See on an Ultrasound
Seven weeks is generally the earliest point where an ultrasound can show meaningful detail. At this stage, a heartbeat should be visible in a normally developing pregnancy. You’d likely see the gestational sac (a dark circle on the screen), the yolk sac (which nourishes the embryo before the placenta takes over), and the fetal pole, which is the small, bright shape that is the embryo itself.
Don’t expect anything that looks like a baby yet. At 7 weeks, the embryo appears as a tiny bright spot with a flickering heartbeat. If your ultrasound is done at the very beginning of week 7 rather than the end, the embryo may be harder to see clearly, and some providers will schedule a follow-up scan a week or two later to get a better look.
Changes in Your Body
While your baby is blueberry-sized, your uterus has already expanded to about the size of a lemon. Before pregnancy it was closer to the size of a small pear, so the change is real but still entirely internal. You won’t have a visible bump yet, though some people notice bloating or a feeling of fullness in the lower abdomen.
This is also the window when early pregnancy symptoms tend to peak or intensify. Nausea, breast tenderness, fatigue, and frequent urination are all common around week 7. These are driven by rising hormone levels, particularly the same hormone (hCG) that made your pregnancy test positive. The intensity varies widely from person to person, and having mild symptoms or none at all doesn’t indicate a problem.
How Growth Speeds Up From Here
At 7 weeks, the embryo is growing at a rate of roughly a millimeter per day. That pace accelerates. By week 8, the embryo will measure around 14 to 16 mm, nearly doubling in size in a single week. By the end of the first trimester at 12 weeks, your baby will be about 6 centimeters long (roughly 2.5 inches) and will have graduated from “embryo” to “fetus,” with all major organ systems in place and recognizable human features like fingers, toes, and earlobes.
The jump from blueberry to lime in just five weeks gives you a sense of how fast development moves during this stage. Even though there’s nothing to see from the outside, the first trimester is when the most complex structural work happens.