The second trimester spans weeks 13 through 27 of pregnancy and is often called the most comfortable stretch of the three. First-trimester nausea typically fades, energy returns, and the baby undergoes dramatic growth, developing from roughly the size of a peach into a nearly two-pound infant with functioning organs and active senses. Here’s what’s happening week by week, what you’ll feel in your own body, and what medical checkpoints to expect.
How the Baby Grows
At the start of the second trimester, all major organs are already formed in miniature. The next 15 weeks are about maturation and rapid size gains. By week 20, the baby measures about 6⅓ inches from crown to rump and weighs around 11 ounces. By the end of the trimester, that weight roughly triples.
Several milestones happen in a predictable sequence. The skeleton begins hardening from soft cartilage into bone. A fine layer of hair called lanugo covers the skin, helping regulate temperature. The baby starts swallowing amniotic fluid, and the kidneys begin producing urine. Fingerprints form. Fat stores slowly build under the skin, giving the baby a less translucent appearance as the weeks progress.
Sensory development accelerates during this period. The ears mature enough to detect sound, and the eyes become sensitive to light, though the eyelids stay fused until later. By the middle of the trimester the baby has regular sleep-wake cycles and responds to stimulation from outside the womb.
When You’ll Feel Movement
One of the most anticipated moments of the second trimester is quickening, the first time you feel the baby move. This typically happens between weeks 16 and 20. If you’ve been pregnant before, you may notice it closer to week 16. First-time mothers more commonly feel it around week 20, partly because the sensation is unfamiliar and easy to mistake for gas or muscle twitches.
An anterior placenta (one that sits between the baby and your belly wall) can muffle early movements and delay your awareness of them by a few weeks. Early kicks often feel like flutters or light tapping. By the late second trimester, movements become unmistakable rolls, jabs, and hiccups that are sometimes visible from the outside.
Changes in Your Body
Your body is doing significant work behind the scenes. Blood volume rises steadily throughout the trimester, driven by hormonal signals, to supply the placenta and growing baby. The uterus expands well above the pelvis. Your provider will start measuring fundal height, the distance from your pubic bone to the top of the uterus, as a quick gauge of growth.
Skin changes are common. Rising melanin production can create brown, tan, or gray patches on the face, a pattern called melasma. Many women also notice a dark vertical line running down the center of the belly, known as the linea nigra. Both typically fade after delivery.
You’ll need roughly 300 extra calories a day during the second trimester, bringing the daily total to about 2,200 calories for most women at a healthy pre-pregnancy weight. Iron, calcium, and folic acid remain especially important. Iron supports the baby’s blood supply and helps prevent maternal anemia, while folic acid continues to reduce the risk of spinal and brain defects.
Total weight gain over the entire pregnancy varies by pre-pregnancy BMI. Overweight women are generally advised to gain 15 to 25 pounds total, while obese women are advised to gain 11 to 20 pounds. For twin pregnancies, the targets are higher, ranging from 25 to 54 pounds depending on starting weight. Most of the noticeable gain begins in the second trimester as the baby, placenta, and amniotic fluid all increase in volume.
Round Ligament Pain and Other Discomforts
As the uterus grows, the two round ligaments that anchor it to the groin stretch longer and wider. A sudden movement, a sneeze, a quick turn in bed, can make these ligaments contract faster than they can accommodate, producing a sharp, stabbing pain on one or both sides of the lower belly. This is round ligament pain, and it’s one of the most common second-trimester complaints.
A few strategies help. Flex your hips or brace your belly before you cough, sneeze, or laugh. Move slowly when changing positions. An elastic belly band can distribute the weight more evenly. For nighttime relief, lie on the side opposite the pain with a pillow between your knees and another tucked under your belly. A daily stretch on hands and knees, lowering your head toward the floor while keeping your hips elevated, gently loosens the ligaments over time.
Other common discomforts include back pain from your shifting center of gravity, nasal congestion caused by increased blood flow to mucous membranes, and leg cramps that tend to strike at night. Some women develop mild swelling in the hands and feet as blood volume continues to climb.
Sleep Position Matters
As the uterus grows heavier, lying flat on your back can compress the large vein that returns blood to the heart. This inferior vena cava compression reduces cardiac output and can cause dizziness, nausea, or a drop in blood pressure. It can also contribute to restless legs and overall poor sleep quality. Side sleeping, particularly on the left side, keeps the vein unobstructed. Placing a pillow between your knees and another behind your back can make this position more comfortable and prevent you from rolling onto your back during the night.
The 20-Week Anatomy Scan
The midpoint ultrasound, usually scheduled around week 20, is the most detailed imaging appointment of pregnancy. A sonographer systematically checks the baby’s heart, brain, spine, kidneys, bladder, stomach, intestines, chest, lungs, limbs, hands, feet, fingers, toes, and facial features including the lips, nose, eyes, and chin. They record the heart rate, measure amniotic fluid volume, evaluate blood flow through the umbilical cord, and note where the placenta is positioned relative to the cervix.
This scan is also when many parents learn the baby’s sex, though that’s optional. If anything looks unusual, your provider may recommend a follow-up scan or additional testing. For most pregnancies, though, the anatomy scan is simply a reassuring confirmation that development is on track.
Glucose Screening for Gestational Diabetes
Between weeks 24 and 28, you’ll be offered a glucose screening test. The U.S. Preventive Services Task Force recommends screening all pregnant people without existing symptoms at 24 weeks or after. The most common approach in the U.S. is a two-step process: you drink a sugary solution, and your blood sugar is measured one hour later. If that initial result is elevated, you return for a longer three-hour test with multiple blood draws to confirm or rule out gestational diabetes.
Gestational diabetes develops when the body can’t produce enough insulin to handle the increased demands of pregnancy. It’s manageable with dietary changes, monitoring, and sometimes medication, but left undetected it can lead to complications for both mother and baby. The screening is quick, and most women pass the first step without needing further testing.
What the Second Trimester Feels Like Overall
For many women, the second trimester brings a genuine sense of relief. The exhaustion and nausea of the first trimester recede, and the physical heaviness of the third trimester hasn’t set in yet. Energy levels rebound, appetite stabilizes, and the pregnancy becomes visible enough to feel real but not yet large enough to limit mobility. It’s typically the window when people feel most like themselves, travel most comfortably, and begin preparing nurseries and birth plans with renewed focus.