At four months pregnant, most women are starting to show a visible bump, though the size varies widely from person to person. The baby is roughly the size of an avocado, with a head that’s now upright and facial features moving into their final positions. This is the beginning of the second trimester, and for many women, it brings a welcome shift: more energy, less nausea, and the first hints of feeling the baby move.
What Your Belly Looks Like
Some women have a clearly rounded bump by month four, while others barely look different in regular clothing. Several factors determine when you start showing. If this is your second or third pregnancy, you’ll likely show earlier because your abdominal muscles have already been stretched from a previous pregnancy and adapt to the growing uterus more quickly. Women with less core muscle tone also tend to show sooner, since their abdominal wall is more relaxed.
Your body type, height, and the position of your uterus all play a role too. Taller women or those with a longer torso often show later because there’s more vertical space for the uterus to expand before it pushes outward. By the end of month four, though, most women notice their waistband tightening and a firmer, rounder shape forming below the belly button.
What the Baby Looks Like at 16 Weeks
By the end of the fourth month, the baby’s head is upright rather than tucked against the chest, which gives the body more human-like proportions. The eyes can move slowly, and the ears are close to reaching their final position on the sides of the head. A scalp hair pattern is forming around week 15, though actual visible hair comes later for most babies.
The skeleton is shifting from soft cartilage to harder bone. Arms and legs are more proportional to the body now, and the baby is making active movements: stretching, flexing, and even making facial expressions. If you have an ultrasound around this time, the scan can assess the brain and face, spine and limbs, heart and chest, and abdominal organs like the stomach, kidneys, and bladder. From 15 weeks onward, it’s also possible to determine the baby’s sex via ultrasound.
When You Might Feel Movement
One of the most anticipated milestones around month four is quickening, the first time you feel the baby move. This typically happens between 16 and 20 weeks, though the timing depends on whether you’ve been pregnant before. Women in their second or later pregnancies often notice it by about 16 weeks because they recognize the sensation. First-time mothers commonly don’t feel it until closer to 20 weeks.
The sensation is subtle and easy to mistake for gas or digestion. Women describe it as fluttering like a butterfly, tiny tapping or pulses, bubbles popping, light rolls or tumbles, or small muscle spasms. It comes and goes at this stage, so don’t worry if you feel it one day and not the next.
Changes to Your Skin
Rising estrogen levels during pregnancy affect pigment cells in the skin, which have estrogen receptors. This can trigger noticeable changes around month four. Melasma, sometimes called “the mask of pregnancy,” shows up as darker patches of skin on the cheeks, forehead, and upper lip. It’s harmless and often fades after delivery, though sun exposure can make it more pronounced.
Many women also notice the linea nigra, a dark vertical line running down the center of the belly. Like melasma, it’s driven by the same hormone-related increase in pigmentation. Existing freckles, moles, and areolas may darken as well.
How Your Body Feels at 4 Months
The second trimester is often called the honeymoon phase of pregnancy, and for good reason. For many women, the morning sickness and deep fatigue of the first trimester fade noticeably. Appetite typically increases, which makes sense since the baby’s growth is accelerating. Some women also feel a burst of energy they haven’t had in weeks, along with a reduction in the anxiety that can accompany early pregnancy.
That said, new discomforts replace the old ones. Round ligament pain is one of the most common. As your uterus expands, the ligaments supporting it stretch and widen, creating an uncomfortable pulling or sharp sensation in the lower abdomen, hips, or groin. It often strikes when you move suddenly: standing up too fast, rolling over in bed, sneezing, or coughing. The pain is brief but can be startling. Wearing an elastic belly band or placing your hands under your belly for support can help ease it.
You may also notice your center of gravity starting to shift as the uterus grows upward out of the pelvis. This subtle change can affect your posture and make certain positions less comfortable than they used to be. Looser, stretchy clothing and supportive shoes make a real difference during this transition.
What an Ultrasound Shows
An ultrasound between 14 and 19 weeks provides the first detailed look at the baby’s anatomy. At this stage, the scan can evaluate brain structure, facial features, spinal alignment, limb development, heart function, and the condition of the placenta and amniotic fluid. This is the point when many parents get their first clear profile image of the baby’s face.
The baby is active during these scans, often seen kicking, stretching, or changing position. You’ll see distinct arms and legs, a visible spine, and the four chambers of the heart beating. If you want to know the sex, this is typically the earliest reliable window for finding out, though some providers prefer to wait until the more detailed anatomy scan around 20 weeks for a definitive answer.