At 7 weeks pregnant, your baby is about the size of a blueberry, measuring roughly 16 to 18 millimeters (just under 3/4 inch) from crown to rump. It doesn’t look much like a baby yet. The head is oversized compared to the body, there’s no clearly formed chin, and the overall shape is curved, almost like a comma. But a surprising amount of development is already underway beneath the surface.
Overall Size and Shape
The embryo at this stage is measured from the top of the head to the bottom of the torso, since the legs are too small and curled to measure reliably. That crown-to-rump length of 16 to 18 millimeters means your baby could sit on the tip of your finger. The head makes up a large portion of the total body, giving the embryo a top-heavy appearance. Earlier in development, a small tail-like extension is visible at the bottom of the spine, but by week 7 it’s actively shrinking as cells in that region are programmed to die off. By the end of the embryonic phase, it disappears entirely.
Facial Features Starting to Form
The face is in its earliest stages and looks nothing like what you’d recognize. Dark spots mark where the eyes are forming, and thin folds of skin are becoming eyelids. The nostrils are just shallow pits on the front of the face. There’s no defined nose bridge, no chin, and the mouth is only a small opening. The inner ear structures are also beginning to take shape, though they won’t be functional for months. Everything is miniature and tightly compressed, which is why the head appears so disproportionately large.
Arms, Legs, and Tiny Digits
This is a big week for limbs. The arms are growing longer, and elbows are now visible for the first time. The legs are a bit behind the arms in development (a pattern that continues even after birth), but toes are becoming visible by the end of the week. The hands and feet still look paddle-like, with fingers and toes not yet fully separated. Movement is happening at a cellular level, but the embryo is far too small for you to feel anything.
Brain and Nervous System
The brain is developing rapidly, already divided into three main sections: the forebrain, midbrain, and hindbrain. These will eventually control everything from thinking and vision to balance and breathing. New brain cells are being produced at an extraordinary rate. The neural tube, which formed a few weeks earlier, has closed and is now specializing into the brain and spinal cord. This is one reason folic acid is so important in early pregnancy: it supports this exact process.
Internal Organs Taking Shape
The liver is one of the most prominent organs at 7 weeks, growing so quickly that it creates a visible bulge on the embryo’s abdomen. Its job right now isn’t digestion. Instead, it’s acting as the main blood cell factory, producing the embryo’s blood supply because the bone marrow isn’t developed enough to do that yet. The liver is also forming its first connections to the gut, with bile ducts beginning to organize.
The digestive tract is dividing into its major sections. The foregut is forming what will become the esophagus, stomach, and the upper part of the small intestine, along with the liver and pancreas. The midgut will become most of the small intestine and the first portion of the large intestine. The hindgut is developing into the lower colon, rectum, and parts of the urinary system. Kidneys are also present in an early form, though they’ll go through several stages of development before reaching their final structure.
What You’ll See on an Ultrasound
If you have an ultrasound at 7 weeks, don’t expect to see anything that looks like a baby. Most 7-week scans are done transvaginally because the embryo is too small to pick up clearly through the abdomen. Here’s what typically shows up on the screen:
- Gestational sac: A dark, circular or oval shape surrounded by the whitish tissue of your uterus. This is the fluid-filled space where the embryo is growing.
- Yolk sac: A small white ring or bubble inside the gestational sac. It’s providing your baby with nutrients and oxygen until the placenta takes over.
- Fetal pole: A thick, whitish shape attached to the yolk sac. This is the embryo itself. It may look curved or oblong, and you won’t be able to make out any specific body parts.
- Heartbeat: Often detectable at this stage. You may see a flickering motion on the screen, and your provider can measure the heart rate.
You won’t be counting fingers or identifying facial features. The embryo is simply too small for that level of detail. Some people can make out the general shape of something inside the sac, while others see what looks like a tiny blob. Both are completely normal. The purpose of a 7-week ultrasound is to confirm the pregnancy is in the right location, check for a heartbeat, and estimate how far along you are based on the embryo’s size.
How Week 7 Compares to Nearby Weeks
Development moves fast at this stage. Just one week earlier, at 6 weeks, the limb buds were barely visible nubs. By week 8, the fingers will start separating, the facial features will become slightly more defined, and the embryo will begin making spontaneous movements (still too small to feel). Week 7 sits right in the middle of this rapid transformation, a point where the basic body plan is locked in and the details are filling in quickly. By the end of week 8, the embryonic period officially ends and the fetal period begins, marking a shift from forming new structures to growing and refining the ones already in place.