The second trimester runs from week 14 through week 27, spanning a total of 14 weeks. The American College of Obstetricians and Gynecologists defines it precisely as 14 weeks and 0 days through 27 weeks and 6 days. This places it roughly in months four, five, and six of pregnancy, and it’s often called the most comfortable trimester as early nausea fades and energy returns.
How the Trimesters Break Down
Pregnancy is divided into three trimesters of roughly equal length. The first trimester covers weeks 1 through 13, the second covers weeks 14 through 27, and the third runs from week 28 until delivery (usually around week 40). Pregnancy weeks are counted from the first day of your last menstrual period, not from conception, so by the time you enter the second trimester, the embryo has actually been developing for about 12 weeks.
If you’re trying to convert weeks to months, the math gets a little messy because calendar months aren’t exactly four weeks long. A rough guide: week 14 falls near the start of month four, and week 27 falls near the end of month six.
What’s Happening With the Baby
The second trimester is a period of rapid growth and development. At week 14, fingerprints begin to form. By week 16, the ears are developed enough that the baby can hear your voice. Limb movement starts early in this trimester, though most people don’t feel it until around week 20, when those first flutters (called “quickening”) become noticeable. By week 19, the baby has a fully unique set of fingerprints.
The baby goes from roughly the size of a lemon at week 14 to about 14 inches long and over 2 pounds by the end of week 27. Organs continue maturing, the nervous system becomes more complex, and a layer of fine hair covers the skin. By the end of the second trimester, the baby’s eyes can open and close.
Physical Changes You’ll Notice
Your belly and breasts grow noticeably as the uterus expands. At prenatal visits, your provider will start measuring the distance from your pubic bone to the top of your uterus (called fundal height) to track growth. Rising hormone levels trigger a cascade of other changes: your body produces more blood, which can make the inside of your nose swell and bleed more easily. The same hormones increase pigment-producing cells in your skin, sometimes creating brown or gray patches on the face (melasma) or a dark vertical line down the belly (linea nigra).
Stretch marks may appear on your belly, breasts, thighs, or buttocks. Small spider veins can show up on your face and legs. Back pain becomes more common as the growing uterus shifts your center of gravity. You might experience leg cramps, dizziness from changes in blood flow, gum sensitivity when brushing, and a clear or white vaginal discharge. Some people also feel mild, irregular tightening in the belly called Braxton Hicks contractions, which are normal practice contractions that come and go.
Key Tests During the Second Trimester
Two major screenings happen during these 14 weeks. The anatomy scan, a detailed ultrasound performed between weeks 18 and 22, is one of the most anticipated appointments of pregnancy. A sonographer takes measurements of the baby’s heart, brain, spine, kidneys, limbs, and facial features. They also check the heart rate, placenta position, umbilical cord blood flow, amniotic fluid level, and your cervix. This is often when parents learn the baby’s sex, if they want to know.
The other routine test is a glucose screening, typically done between weeks 24 and 28, to check for gestational diabetes. You’ll drink a sugary solution and have your blood drawn an hour later. If the result comes back above 140 mg/dL, a longer follow-up test is scheduled to confirm whether gestational diabetes is present.
Weight Gain Guidelines
Weight gain picks up during the second trimester compared to the first. The recommended rate depends on your pre-pregnancy BMI. For those who started at a normal weight (BMI 18.5 to 24.9), the target is about 1 pound per week. The same rate applies if you were underweight before pregnancy. If you were overweight (BMI 25 to 29.9), the recommendation drops to about 0.6 pounds per week. For those with a BMI of 30 or higher, it’s roughly half a pound per week. These are averages, and individual weeks will vary.
Warning Signs to Take Seriously
Most of the second trimester is uneventful, but certain symptoms call for immediate medical attention. A headache that won’t go away or gets progressively worse, especially with blurred vision, can signal dangerously high blood pressure. Extreme swelling in your hands or face, to the point where you can’t bend your fingers or your eyes look puffy, is another red flag for the same condition.
Other urgent symptoms include a fever of 100.4°F or higher, sharp or worsening abdominal pain, vaginal bleeding beyond light spotting, or leaking fluid (which could indicate ruptured membranes). Trouble breathing, chest pain, a racing heartbeat, or sudden severe leg swelling with redness and warmth also warrant a call to your provider right away. Once you start feeling the baby move regularly (usually by week 24 to 25), a noticeable decrease in movement is worth reporting too.