At 7 weeks pregnant, your baby is about 5 to 10 millimeters long, roughly the size of a blueberry. That’s measured from the top of the head to the bottom of the torso (called crown-to-rump length), since the legs are too small and curled to measure. Despite being tiny enough to sit on the tip of your pinky finger, a surprising amount of development is already underway.
What 5 to 10 Millimeters Looks Like
A blueberry is the go-to comparison for a 7-week embryo, and it’s a good one. The entire gestational sac, which is the fluid-filled structure surrounding the embryo, is larger, but the embryo itself is that small. To put it another way, if you held a standard pencil eraser between your fingers, your baby would be roughly that diameter or slightly smaller.
Growth at this stage is rapid. Just one week earlier, the embryo was closer to 2 to 4 millimeters. By week 8, it will nearly double again. This exponential pace means visible changes are happening daily, even though you can’t feel any of them yet.
What’s Developing at 7 Weeks
Size alone doesn’t capture how much is going on inside that blueberry-sized embryo. The heart, which started as a simple tube just days ago, is now beating at roughly 120 to 154 beats per minute. That’s about twice the resting heart rate of an adult. At 6 weeks the heart rate typically starts around 100 to 120 bpm, then climbs steadily over the following two to three weeks.
Small paddle-shaped limb buds are forming where arms and legs will eventually be. The face is beginning to take shape in a way that would be hard to recognize but is structurally important: the tissue that will become the upper lip and the border of the nostrils is fusing together this week. Tiny dark spots mark where the eyes will develop. The brain is growing quickly, producing new nerve cells at an extraordinary rate, and the head makes up a large proportion of the overall body.
Internal organs are also getting started. The kidneys, liver, and lungs exist in very early forms, and the digestive tract is beginning to take shape as a simple tube running through the body.
What You’d See on an Ultrasound
If you have an ultrasound around 7 weeks, it will almost certainly be a transvaginal scan rather than the over-the-belly type, because the embryo is still too small for an external probe to capture clearly. On the screen, your provider can typically identify several structures: the gestational sac, a smaller yolk sac that’s providing early nourishment, the fetal pole (which is the first visible outline of the embryo), and a flickering heartbeat.
The embryo itself looks like a small bright spot within the sac. Don’t expect it to look like a baby yet. At this stage it resembles a tiny curved bean more than anything recognizably human. The heartbeat is often the most reassuring finding, and many parents describe hearing or seeing it for the first time as the moment the pregnancy starts to feel real.
What’s Happening in Your Body
While your baby is blueberry-sized, your uterus is already changing. Before pregnancy it’s roughly the size of a small pear. By 7 weeks it has started to expand, though not enough for anyone else to notice. Most of the physical changes you’re experiencing are driven by hormones rather than the uterus itself.
Progesterone, which rises steadily through the first trimester, is the main culprit behind fatigue and constipation. It relaxes smooth muscle tissue throughout your body, which slows digestion and can leave you feeling sluggish. Meanwhile, rapidly rising levels of pregnancy hormone (hCG) are likely behind the nausea that peaks for many people right around this time.
The NHS lists a wide range of symptoms common at 7 weeks:
- Morning sickness that can strike at any time of day, not just mornings
- Sore or tender breasts
- Extreme fatigue
- A metallic taste in your mouth
- Heightened sense of smell and new food aversions
- Bloating and cramping similar to mild period pains
- Light spotting, which is common and usually harmless
- Skin changes, including darker patches on the face sometimes called the “mask of pregnancy”
Not everyone experiences all of these, and some people have very few symptoms at 7 weeks. That’s normal too. Symptom intensity doesn’t reliably predict how healthy the pregnancy is.
How Growth Compares Week to Week
Tracking your baby’s size each week can help make the invisible feel more concrete. At 5 weeks, the embryo is roughly the size of a sesame seed. By 6 weeks, it’s a lentil. At 7 weeks, a blueberry. And by 8 weeks, it reaches the size of a raspberry, around 1.5 centimeters. The pace only accelerates from here: by the end of the first trimester at 12 weeks, the baby will be roughly 5 to 6 centimeters long, about the length of a lime.
The jump from blueberry to lime in just five weeks gives you a sense of how dramatically things change during the first trimester, even though your belly won’t show it for several more weeks.