The second trimester of pregnancy spans from week 13 through the end of week 27. That’s roughly the middle three months, and for many people, it’s the stretch where nausea fades, energy returns, and the pregnancy starts to feel real. Here’s what’s happening during those 15 weeks, for both you and your baby.
When the Second Trimester Starts and Ends
Pregnancy is divided into three trimesters of roughly equal length. The first trimester covers weeks 1 through 12, the second runs from week 13 through week 27, and the third picks up at week 28 and continues until delivery. You might see slight variation depending on the source (some round the start to week 14), but week 13 to 27 is the standard range used by most major medical institutions.
One reason this milestone matters: the risk of pregnancy loss drops significantly once you cross into the second trimester. About 2 to 3 percent of pregnancies are lost in the second trimester, compared to much higher rates in the first. After 20 weeks, that number falls below 0.5 percent.
How Your Baby Grows During These Weeks
Your baby enters the second trimester at roughly 3.5 inches long and about 1.5 ounces. By week 20, the midpoint, they’ve grown to about 6.3 inches (measured from the top of the head to the tailbone) and around 11 ounces. By the end of the trimester, your baby is roughly 2 pounds and over a foot long, with functioning organs and increasingly coordinated movements.
Key developmental milestones happen on a loose but predictable schedule. Between weeks 13 and 16, the bones continue to harden and facial features become more defined. Around weeks 17 to 20, hearing begins to develop, meaning your baby can start responding to sounds outside the womb. Between weeks 21 and 24, a fine layer of soft hair called lanugo covers the body, and the sucking reflex starts forming. By the final weeks of the trimester, the lungs are developing the structures they’ll eventually need to breathe air, though they aren’t ready yet.
When You’ll Feel Movement
One of the most anticipated moments of the second trimester is feeling your baby move for the first time, known as quickening. If this is your first pregnancy, you’ll typically notice it around week 20. If you’ve been pregnant before, you may feel it as early as week 16, partly because you recognize the sensation. Early movements often feel like flutters, bubbles, or light tapping rather than full kicks.
Physical Changes You Can Expect
The second trimester brings a noticeable shift in energy. The fatigue and nausea that often define the first trimester tend to ease, and many people feel more like themselves again. That said, a new set of physical changes takes over as your body accommodates a rapidly growing baby.
Skin changes are among the most common. Hormonal shifts increase the production of pigment-containing cells in your skin, which can cause brown, tan, or gray patches on the face (called melasma) and a dark vertical line down the center of your belly (linea nigra). Stretch marks may appear on the belly, breasts, thighs, or buttocks as the skin stretches. Small spider veins can also show up on the face and legs.
Your belly becomes visibly larger during this trimester, and you’ll likely start needing maternity clothes. Breast changes continue as your body prepares for milk production. Some people also notice nasal congestion, leg cramps, mild swelling in the ankles and feet, and occasional dizziness as blood volume increases.
Nutrition and Weight Gain
Caloric needs increase modestly in the second trimester. The CDC recommends adding about 340 extra calories per day during these weeks, which is roughly the equivalent of a yogurt parfait or a peanut butter sandwich. That number rises to about 450 extra calories per day in the third trimester.
Total pregnancy weight gain depends on your pre-pregnancy BMI. For someone who started at a normal weight (BMI 18.5 to 24.9), the recommended total gain across the entire pregnancy is 25 to 35 pounds. For those who were overweight before pregnancy (BMI 25 to 29.9), the range is 15 to 25 pounds. Underweight individuals are advised to gain 28 to 40 pounds total, while those with a BMI of 30 or higher are guided toward 11 to 20 pounds. Most of this weight accumulates during the second and third trimesters, since the first trimester adds very little.
Prenatal Tests and Screenings
Two major screenings happen during the second trimester. The first is the anatomy scan, a detailed ultrasound typically performed around week 20. This is the appointment where a sonographer takes images and measurements of your baby’s heart, brain, spine, kidneys, lungs, limbs, and facial structures. They also check the fetal heart rate, evaluate blood flow through the umbilical cord, measure amniotic fluid levels, and assess the position of the placenta. If you want to learn the baby’s sex, this is usually the ultrasound that reveals it.
The second major test screens for gestational diabetes. Between weeks 24 and 28, a blood test checks how your body processes sugar. This test also evaluates your blood count and iron levels. Gestational diabetes affects a significant number of pregnancies and, when caught early, is manageable with dietary changes and monitoring.
Your provider will also continue routine checks at each visit, including blood pressure readings, urine tests, and measurements of your uterus to track growth. Prenatal visits during the second trimester are typically scheduled every four weeks.
What Makes This Trimester Different
The second trimester occupies a unique middle ground. The high-risk uncertainty of the first trimester has passed, and the physical demands of the third trimester haven’t arrived yet. Energy levels are generally higher, appetite stabilizes, and the pregnancy becomes visible to others. It’s the stretch when many people share the news publicly, start preparing the nursery, and feel their baby’s first movements.
That doesn’t mean it’s entirely smooth. Round ligament pain (sharp or aching sensations in the lower belly as ligaments stretch to support the uterus), back pain, and heartburn are all common. Sleep may become harder as your belly grows. But for most people, the second trimester is the period of pregnancy that feels the most manageable, both physically and emotionally.