At 13 weeks pregnant, your baby measures roughly 7 to 8 centimeters from head to rump, about the size of a lemon. Your body is on the cusp of the second trimester, and while a visible bump varies widely from person to person, real changes are happening both inside and out.
What the Baby Looks Like at 13 Weeks
By week 13, the fetus has shifted from looking like a generic embryo to something recognizably human. The head, which was oversized relative to the body in earlier weeks, is starting to grow more proportionally. Vocal cords are forming this week, and the bones are continuing to harden. The skin is still translucent enough that blood vessels are visible beneath it. Fingerprints haven’t appeared yet, but they’ll start forming around week 14.
The baby weighs roughly 23 to 28 grams at this stage. Arms and legs have lengthened, fingers and toes are distinct, and the intestines, which temporarily grew into the umbilical cord because the abdomen was too small, have moved back into the body. If you have an ultrasound this week, you’ll likely see the baby moving, though you won’t feel those movements for several more weeks.
What Your Body Looks Like
Whether you’re “showing” at 13 weeks depends almost entirely on your abdominal muscle tone and whether this is your first pregnancy. At this point, the top of the uterus (the fundus) sits just above the pubic bone. It hasn’t risen high enough to push noticeably against the abdominal wall for most people. A visible bump typically becomes obvious closer to week 20, when the uterus rests against the front of the abdomen.
If your abdominal muscles are strong, they hold the uterus back against the spine, and there may be no bump at all yet. If the muscles are more relaxed, possibly from a previous pregnancy, the pressure of the growing uterus can create a noticeable bulge earlier. Both are normal. Many people at 13 weeks describe looking more “bloated” than pregnant, with their regular pants feeling tight but maternity clothes feeling too loose.
Skin Changes You Might Notice
Hormonal shifts are already affecting your skin by week 13, even if the most visible changes come later. The placenta produces a hormone that stimulates melanin production, which is responsible for skin pigment. This same mechanism darkens your areolas, can cause patches of darker skin on the face (sometimes called the “mask of pregnancy”), and eventually creates the linea nigra, a dark vertical line running down the center of your belly. The linea nigra usually becomes visible around week 20, but some people notice a faint line forming earlier.
How You’ll Likely Feel This Week
Week 13 is a turning point for many people in terms of daily comfort. The nausea and exhaustion that dominated the first trimester often begin to ease as you enter the second trimester. Energy levels typically rebound, and many people describe this stretch as the most comfortable part of pregnancy. That said, morning sickness doesn’t follow a strict schedule. For some, it lingers until around week 20.
Other common experiences at this stage include breast tenderness that’s been present for weeks, occasional headaches, and increased appetite as nausea fades. You may also notice that your sense of smell, which was heightened in the first trimester, starts to settle down.
Screening Tests Around This Window
If you haven’t had a nuchal translucency scan yet, week 13 is near the end of the window for this ultrasound. It’s performed between weeks 11 and 13, because after week 14, the pocket of fluid at the back of the baby’s neck gets reabsorbed and becomes difficult to measure. The scan measures that fluid to screen for a higher likelihood of chromosomal conditions like Down syndrome, as well as certain congenital heart conditions. It’s a screening tool, not a diagnosis, so an unusual result leads to further testing rather than a definitive answer.
Miscarriage Risk Drops Significantly
One of the reasons many people share pregnancy news around the 13-week mark is that the risk of miscarriage drops dramatically after week 12. Early miscarriage occurs in roughly 10 to 20 percent of recognized pregnancies, but second-trimester loss is far less common, estimated at 3 to 4 percent. Reaching 13 weeks is a meaningful milestone, and it’s why this is often the point where pregnancy starts to feel more “real” emotionally, not just physically.