The second trimester of pregnancy lasts about 14 weeks, running from week 14 through week 27. The American College of Obstetricians and Gynecologists (ACOG) defines it precisely as 14 weeks and 0 days through 27 weeks and 6 days, placing it squarely in the middle stretch of a full 40-week pregnancy.
You may see slightly different cutoffs depending on the source. The U.S. Office on Women’s Health lists the second trimester as weeks 13 through 28, which shifts the boundaries by about a week on each end. In practice, the difference rarely matters for your care. Your provider will track your pregnancy by exact gestational age rather than trimester labels.
Why the Week Range Varies by Source
Pregnancy is 40 weeks long, and dividing it into three equal parts would give you roughly 13.3 weeks per trimester. That doesn’t land on a clean number, so different medical organizations round differently. ACOG draws the line at the start of week 14; some international guidelines and popular pregnancy apps place it at week 13. Either way, the second trimester covers the fourth, fifth, and sixth months of pregnancy and ends just before the third trimester begins at week 28.
How Your Baby Grows During These Weeks
The second trimester is a period of rapid growth. At week 14, the fetus measures about 3.5 inches from head to tailbone and weighs roughly 1.5 ounces, comparable to a small lemon. By week 26, that same measurement jumps to around 9 inches, and the weight reaches nearly 2 pounds. Bones harden, facial features become more defined, and the nervous system matures enough that the baby begins responding to sound and light.
This trimester also marks the earliest edge of what doctors call “periviability,” the point at which survival outside the womb becomes possible with intensive medical support. Survival rates vary widely at these early gestational ages. At 22 weeks, reported survival ranges from 0% to 37% depending on the hospital and level of intervention. By 24 completed weeks, survival rises to roughly 70% or higher in well-equipped neonatal units. By 25 weeks, it reaches 59% to 86%. These numbers have improved steadily over the past decade.
What You Can Expect to Feel
Many people call the second trimester the most comfortable stretch of pregnancy. First-trimester nausea typically fades, and the fatigue that defined those early weeks often lifts. Energy levels tend to rebound somewhere around weeks 14 to 16.
The most anticipated milestone is feeling the baby move for the first time, often called “quickening.” This usually happens between weeks 16 and 22, though first-time parents may not notice it until closer to week 20. Early movements feel like flutters or bubbles rather than the distinct kicks that come later.
Hormonal shifts increase melanin production in your skin, which can cause a dark vertical line down the center of your belly (linea nigra) and brown or grayish patches on your face, sometimes called melasma. Both are harmless and typically fade after delivery. Your belly grows noticeably during this stretch, and you can expect to gain about 1 pound per week on average, though the normal range runs from about 0.7 to 1.4 pounds per week.
Key Screenings and Tests
Two major screenings fall within the second trimester, and knowing when they happen helps you plan ahead.
The anatomy scan, sometimes called the 20-week ultrasound, is typically scheduled between weeks 18 and 22. This is the most detailed ultrasound of your pregnancy. A technician takes images and measurements of the baby’s heart, brain, spine, kidneys, limbs, and facial structures. They also check the position and health of the placenta, measure amniotic fluid levels, and assess blood flow through the umbilical cord. For many parents, this is the appointment where they learn the baby’s sex.
The glucose screening test for gestational diabetes is done between weeks 24 and 28. You’ll drink a sugary solution and have your blood drawn afterward to see how your body processes the sugar. If the initial screen comes back elevated, a longer follow-up test confirms whether gestational diabetes is present. This screening is routine for nearly all pregnancies.
Sleep Position in the Second Trimester
Sleep position is a common concern once the belly starts growing. Current evidence shows that before 28 weeks, your sleeping position does not affect pregnancy outcomes. Starting at 28 weeks, which is right at the transition into the third trimester, you should aim to fall asleep on your side. Sleeping on the right side appears to be just as safe as the left, despite older advice that specifically recommended the left side. If you wake up on your back, simply roll over. The key is the position you settle into at the start of sleep.