At 15 weeks, your baby sits just above your pubic bone, nestled inside a uterus that has grown to roughly the size of a small melon. From head to bottom, the baby measures about 4¾ inches (12 centimeters) and weighs around 4 ounces (110 grams), comparable to an apple. You likely can’t feel movement yet, but there’s a lot happening in that small space.
Where the Uterus Sits Right Now
Around 13 to 14 weeks, the top of your uterus (called the fundus) rises just above the pubic bone. By week 15, it’s sitting slightly higher, roughly halfway between your pubic bone and your belly button. This is why many people start to notice a visible bump around this time, though it varies widely depending on body type and whether this is a first pregnancy.
Your provider may begin measuring fundal height at upcoming appointments, using a tape measure from your pubic bone to the top of the uterus. At 15 weeks it’s still early for that measurement to be reliable, but the physical shift upward is what makes the pregnancy more visible from the outside and often brings some relief from the bladder pressure of the first trimester.
How Big Your Baby Is
At 4¾ inches crown to rump and about 4 ounces, your baby has roughly quadrupled in length since the end of the first trimester. The legs are now longer than the arms, and the body proportions are starting to look more balanced. In the first trimester, the head made up nearly half the body’s length. By 15 weeks, the torso and limbs are catching up.
What Your Baby’s Body Is Doing
The skeleton is actively hardening. Bone formation in the spine started around weeks 10 and 11, beginning with the vertebrae in the neck and upper back. By 15 weeks, ossification has spread through the cervical, thoracic, lumbar, and sacral vertebrae. The skull bones are forming through a different process, with flat bone plates developing directly from tissue rather than from cartilage. The long bones in the arms and legs have been hardening since even earlier in development. Your baby’s skeleton is still mostly cartilage, but it’s gradually becoming the framework of real bone.
The digestive system is surprisingly active. The intestines are producing meconium, a substance that will become your baby’s first bowel movement after birth. At this stage, meconium has been detected in the lower intestines and is starting to fill the colon. Interestingly, the greenish color most people associate with meconium hasn’t developed yet. Until around 22 weeks, the intestinal contents are actually whitish because the bile pigment responsible for the green color isn’t being produced in significant amounts.
The heart is beating at roughly 120 to 160 beats per minute, about twice as fast as yours. This rate stays fairly consistent through much of pregnancy, though it does decrease slightly as the baby gets closer to term.
Movement You Can’t Feel Yet
Your baby is moving constantly at 15 weeks: flexing arms and legs, curling fingers, turning the head. Eye movements can be seen on ultrasound starting around 14 to 15 weeks. These aren’t purposeful movements yet but rather the developing nervous system testing connections between the brain and muscles. Most first-time mothers don’t feel any of this until 18 to 22 weeks. If you’ve been pregnant before, you might notice faint flutters a bit earlier, sometimes around 16 weeks.
Sensory Development So Far
Your baby’s eyes are formed but sealed shut. The eyelids won’t begin to open until around 26 weeks, and the ability to detect light doesn’t emerge until closer to 31 weeks. The ears are developing but aren’t yet capable of processing sound in any meaningful way. Over the next several weeks, the auditory system will mature enough for the baby to begin responding to loud noises and the rhythm of your voice, but at 15 weeks, that’s still ahead.
A thin layer of fine hair called lanugo will start covering the baby’s skin between weeks 16 and 20. This soft, feathery hair serves a practical purpose: it helps a waxy coating called vernix stick to the skin, which protects the baby from the constant exposure to amniotic fluid. Without that barrier, the fluid could irritate the delicate skin. At 15 weeks, the skin is still extremely thin and translucent, with blood vessels clearly visible underneath.
What May Happen at Your Appointments
Week 15 falls within the window for a blood test called the quad screen, which is typically offered between weeks 15 and 20. This test measures four substances in your blood to estimate the chance of certain conditions, including Down syndrome, Edwards syndrome, and neural tube defects like spina bifida. It’s a screening test, not a diagnostic one, meaning an abnormal result indicates a higher probability and usually leads to further testing rather than a definitive answer.
If you have an ultrasound at 15 weeks, you may be able to learn the baby’s sex. After 14 weeks, ultrasound predictions of biological sex are highly accurate. Many providers, however, schedule the detailed anatomy scan closer to 18 to 20 weeks, so you may need to wait a few more weeks for that confirmation. At 15 weeks, the ultrasound image will show a baby that looks unmistakably human, with clearly defined limbs, a profile view of the face, and visible movement in real time.