The second trimester of pregnancy runs from week 13 through the end of week 27. It’s often called the most comfortable stretch of pregnancy: first-trimester nausea typically fades, energy returns, and the baby grows from roughly 3.5 inches long to about 9 inches, gaining nearly 2 pounds by the end of this period. For many people, it’s when pregnancy starts to feel real, with a visible bump, noticeable movement, and major prenatal screenings all happening within these 15 weeks.
How Your Baby Develops
At the start of the second trimester, around week 14, the fetus is about 3.5 inches long (measured from the top of the head to the tailbone) and weighs roughly 1.5 ounces. By week 26, that same measurement stretches to about 9 inches, and weight jumps to nearly 2 pounds. That’s an enormous amount of growth in a short window.
The major organs formed during the first trimester now begin to mature and function. The heart pumps several quarts of blood per day. The kidneys start producing urine, which becomes part of the amniotic fluid. The lungs are developing the tiny air sacs they’ll eventually need to breathe, though they won’t be ready to work on their own until much later. Bones harden, facial features become more defined, and fingerprints form.
One of the most exciting milestones is movement. Most people first feel flutters, sometimes called “quickening,” between weeks 16 and 22. Early on these can feel like gas bubbles or light tapping. By the end of the second trimester, kicks and rolls become unmistakable. The baby also develops hearing during this period, responding to loud sounds and even the rhythm of your voice.
Changes in Your Body
The most visible change is your growing belly. As the uterus expands to make room, your center of gravity shifts, which can cause lower back pain. Rising hormone levels trigger your body to produce more blood, increasing total blood volume significantly. This extra circulation is essential for the placenta and baby, but it can also leave you feeling dizzy or lightheaded, especially when you stand up quickly.
Skin changes are extremely common. Hormone-driven increases in melanin, the pigment that gives skin its color, cause several noticeable effects. Melasma, sometimes called “the mask of pregnancy,” appears as brown, tan, or gray patches on the face. The linea nigra, a dark vertical line about a quarter to half an inch wide, runs from the pubic bone toward the belly button (and sometimes past it). It’s more visible in people with darker complexions and tends to darken as pregnancy progresses. You may also notice stretch marks appearing on your belly, breasts, thighs, or buttocks, along with small spider veins on your face and legs.
Breast tenderness from the first trimester often eases, though your breasts continue to grow. Nasal congestion, mild swelling in the ankles and feet, and leg cramps are all typical. Many people also notice their gums bleed more easily when brushing, another effect of increased blood flow.
Key Prenatal Screenings
The second trimester includes two of the most important routine tests in prenatal care.
The Anatomy Scan
Around week 20, you’ll have a detailed ultrasound commonly called the anatomy scan. A sonographer takes pictures and measurements of the baby’s heart, brain, spine, kidneys, lungs, stomach, intestines, arms, legs, hands, feet, and facial features. They also record the heart rate, check blood flow through the umbilical cord, look at the position of the placenta, measure the amount of amniotic fluid, and examine your cervix. This scan is the most thorough look at the baby’s physical development before birth, and it’s also when many people learn the sex if they want to know. The appointment typically takes 30 to 45 minutes.
Glucose Screening
Between weeks 24 and 28, you’ll be screened for gestational diabetes. In the most common version, you drink a sugary liquid and have your blood drawn one hour later to check your blood sugar level. No fasting is required for this initial screen. If your results come back high, you’ll return for a longer follow-up test: this one requires fasting overnight, drinking a more concentrated glucose solution, and having blood drawn at three separate intervals over three hours. Gestational diabetes is manageable when caught early, which is why routine screening is standard.
Nutrition and Energy Needs
Calorie needs increase during the second trimester, but not by as much as you might expect. The general recommendation is about 300 additional calories per day, bringing the total for most people to around 2,200 calories daily. That’s roughly equivalent to an extra snack: a handful of nuts with a piece of fruit, or a yogurt with granola.
Quality matters more than quantity. Iron needs rise because of the increased blood volume, and many prenatal vitamins include it for this reason. Calcium supports the baby’s developing bones. Omega-3 fatty acids, found in fish like salmon, support brain development. Staying well hydrated helps with the increased blood production and can ease common complaints like constipation and headaches.
Common Discomforts and How to Manage Them
Round ligament pain is one of the hallmarks of the second trimester. As the uterus grows, the ligaments supporting it stretch, causing sharp or aching pain on one or both sides of the lower abdomen. It’s usually triggered by sudden movements like standing up, coughing, or rolling over in bed. This is normal and temporary, though it can be startling the first time it happens.
Sleep can become more challenging as your belly grows. Some providers recommend side sleeping, particularly on the left side, to keep the weight of the uterus off the large blood vessels that run along the spine. That said, experts note that the data on back sleeping causing harm is limited, and the stress of trying to maintain an uncomfortable position all night may be counterproductive. Using a pillow between your knees or behind your back can help you find a comfortable position without overthinking it.
Heartburn often ramps up as the growing uterus pushes the stomach upward. Eating smaller, more frequent meals and avoiding spicy or acidic foods before bed can help. Leg cramps, especially at night, are also common and often improve with gentle stretching and adequate hydration.
Warning Signs to Take Seriously
While the second trimester is generally the most comfortable phase, certain symptoms require immediate medical attention. The CDC identifies several urgent warning signs during pregnancy that can indicate life-threatening conditions like preeclampsia, placental problems, or preterm labor.
- Severe headache that won’t go away with medication and fluids, or one that starts suddenly with intense pain
- Vision changes such as flashes of light, blind spots, blurriness, or seeing double
- Extreme swelling of the hands or face, beyond the mild puffiness that’s typical in later pregnancy
- Fever of 100.4°F or higher
- Trouble breathing that comes on suddenly or worsens over time
- Severe belly pain that doesn’t go away, especially if it starts suddenly or gets progressively worse
- Chest pain or rapid heartbeat, particularly if accompanied by dizziness or difficulty talking
- A noticeable decrease in the baby’s movement once you’ve established a pattern of feeling kicks, typically in the later weeks of this trimester
Preeclampsia, a dangerous blood pressure condition, can develop as early as 20 weeks. The combination of a persistent headache, vision changes, and sudden facial or hand swelling is its classic cluster of symptoms. Early detection makes a significant difference in outcomes, which is why blood pressure and urine checks are part of every routine prenatal visit during this period.