The second trimester of pregnancy is 14 weeks long, running from week 14 through week 27. More precisely, it spans from 14 weeks and 0 days to 27 weeks and 6 days of gestation, as defined by the American College of Obstetricians and Gynecologists (ACOG). That puts it roughly in the fourth, fifth, sixth, and seventh months of pregnancy.
When the Second Trimester Starts and Ends
Pregnancy is divided into three trimesters across 40 total weeks. The first trimester covers the first day of your last menstrual period through 13 weeks and 6 days. The second trimester picks up at exactly 14 weeks and 0 days and lasts through 27 weeks and 6 days. The third trimester then runs from 28 weeks to delivery, typically around 40 weeks.
Some sources round slightly differently, with Mayo Clinic noting that week 13 is when bones begin to harden and week 27 “marks the end of the second trimester.” This can create confusion about whether week 13 or week 14 is the true starting line. The clinical definition from ACOG is the most widely used: week 14 through week 27, giving you a full 14 weeks in this middle stretch.
What Happens to Your Body
For many people, the second trimester is the most comfortable phase of pregnancy. Morning sickness typically fades as levels of the early-pregnancy hormone hCG drop and your body adjusts to rising estrogen and progesterone. The extreme fatigue and breast tenderness from the first trimester usually ease up too.
Your uterus grows significantly during these 14 weeks. Around 12 weeks it becomes large enough to feel through the abdominal wall, and by about 20 weeks it reaches the height of your belly button, making the pregnancy clearly visible. That rapid uterine growth can cause aching in your lower abdomen as the ligaments supporting it stretch. On the upside, the uterus rises out of the pelvic cavity during this time, which often relieves the constant need to urinate that’s common in the first trimester.
Other changes you may notice include increased appetite, nasal congestion or nosebleeds, skin pigmentation changes on the face or abdomen, varicose veins, and a white vaginal discharge called leukorrhea. Heartburn, indigestion, and constipation can continue from the first trimester. As you gain weight, backaches may develop, especially later in the second trimester.
Weight Gain During These Weeks
Steady weight gain becomes more important starting at week 14. If you began pregnancy at a healthy weight or underweight, the general guideline is to gain about 1 pound (0.5 kilogram) per week from week 14 through delivery. That pace applies across both the second and third trimesters, so over the 14 weeks of the second trimester alone, you’d expect to gain roughly 14 pounds if you’re following that target. Your specific recommendation may differ based on your pre-pregnancy weight.
Key Screenings and Tests
Two important screenings happen during the second trimester. Between weeks 15 and 20, a blood test screens for certain birth defects. Then around weeks 18 to 20, you’ll have the anatomy ultrasound, where a provider checks all the major structures of the baby’s body. This is often the scan where parents first get a detailed look at their baby and, if they want, learn the sex.
Fetal Development at a Glance
The second trimester is described as a period of rapid growth and development. At the start, around week 13 to 14, your baby’s bones are beginning to harden. Over the following weeks, the baby grows from a few inches long to roughly 14 inches by week 27. You’ll likely start to feel movement, sometimes called quickening, between weeks 16 and 25, with first-time parents often noticing it closer to weeks 20 to 22. By the end of the second trimester, the baby’s organs are developing but not yet mature enough to function independently, which is why the third trimester focuses on weight gain and organ maturation.
Warning Signs to Watch For
While the second trimester is generally lower-risk than the first, certain symptoms call for immediate medical attention at any point in pregnancy. These include a severe headache that won’t go away or comes with blurred vision, vaginal bleeding beyond light spotting, fluid leaking from the vagina, severe or sudden abdominal pain, a fever of 100.4°F or higher, and extreme swelling in the hands or face.
Once you start feeling your baby move regularly, a noticeable decrease or stop in movement is also a reason to seek care right away. The same goes for sudden shortness of breath, chest pain or a racing heartbeat, severe swelling or pain in one leg, or any thoughts of self-harm. These are rare, but recognizing them early makes a significant difference in outcomes.