The second trimester of pregnancy spans from week 14 through week 27, covering the middle stretch of a full-term pregnancy. For many people, it’s the most comfortable trimester: first-trimester nausea typically fades, energy returns, and the baby undergoes rapid growth and development. It’s also when you’ll likely feel your baby move for the first time and have a detailed anatomy scan.
When the Second Trimester Starts and Ends
According to the American College of Obstetricians and Gynecologists, the second trimester officially runs from 14 weeks and 0 days to 27 weeks and 6 days. The first trimester covers everything up to 13 weeks and 6 days, and the third trimester begins at 28 weeks. This middle stretch is often called the period of “rapid growth and development” because the baby’s major organs, which formed during the first trimester, now mature and become functional.
How Your Body Changes
The most welcome change for many people is a noticeable boost in energy. The fatigue and nausea that define the first trimester often lift in the early weeks of the second trimester, replaced by what’s commonly described as an energy burst. You’ll also start visibly showing, as the uterus expands well above the pelvis.
Hormonal shifts increase the number of pigment-producing cells in your skin, which can cause brown, tan, or gray patches on the face (a condition called melasma) and a dark vertical line down the center of your belly known as linea nigra. The skin around your nipples may darken as well. Stretch marks, ranging from reddish-brown to silver or purple, commonly appear on the belly, breasts, buttocks, and thighs as the skin stretches. Some people also notice small spider veins on the face and legs.
Round ligament pain is another hallmark of this trimester. As the ligaments supporting your uterus stretch, you may feel sharp or achy pains on one or both sides of your lower belly, especially when changing positions quickly. This is normal, though it can be startling the first time it happens.
Weight Gain Guidelines
Steady weight gain becomes more important starting around week 14. If you began pregnancy at a healthy weight, the general guideline is to gain about 1 pound (0.5 kilogram) per week through delivery. The exact target varies based on your pre-pregnancy weight, so the recommended range is different for people who started out underweight, overweight, or carrying multiples.
How the Baby Develops Week by Week
At the start of the second trimester, your baby’s skeleton begins to harden, starting with the skull and the long bones of the arms and legs. Red blood cells are forming in the spleen, and the scalp hair pattern is taking shape. By week 16, the eyes can move slowly, the ears are nearly in their final position, and limb movements are coordinated enough to show up clearly on ultrasound.
Around weeks 17 to 20, the brain region controlling motor movement is fully formed and the digestive system starts working. Toenails develop, and the baby becomes more active, rolling and flipping. A greasy coating called vernix begins covering the skin for protection, and the baby starts releasing urine into the amniotic fluid, which now makes up most of the fluid surrounding them.
Week 20 is a milestone: this is often when you first feel your baby move, a sensation called quickening. Your baby is now sleeping and waking on a regular cycle and can be startled awake by noise or your movements. By week 21, a fine layer of downy hair covers the entire body, and the sucking reflex is developing.
In the final weeks of the second trimester, development accelerates further. Eyebrows and hair become visible. Fingerprint and footprint patterns form as ridges appear on the palms and soles. Rapid eye movements begin around week 23, and the lungs start producing surfactant, a substance that will eventually allow the air sacs to inflate and function after birth. By week 25, the baby may move in response to familiar sounds like your voice.
Key Screenings and Tests
The anatomy scan is one of the most anticipated appointments of pregnancy. This detailed ultrasound happens between 18 and 22 weeks and gives a thorough look at the baby’s development. The technician takes measurements and images of the heart, brain, spine, kidneys, lungs, stomach, limbs, and even individual fingers and toes. They also record the heart rate, check blood flow through the umbilical cord, evaluate the placenta’s position, measure the amount of amniotic fluid, and examine your cervix. This is also typically when you can learn the baby’s sex, if you choose to.
Between 24 and 28 weeks, most pregnant people have a glucose screening test to check for gestational diabetes. The standard approach involves drinking a sugary solution and having your blood drawn an hour later. If the initial result is elevated, a longer follow-up test (lasting two or three hours with multiple blood draws) determines whether gestational diabetes is present. Early detection matters because managing blood sugar during pregnancy reduces risks for both parent and baby.
The CDC also recommends getting the Tdap vaccine (which protects against whooping cough, tetanus, and diphtheria) during weeks 27 through 36, ideally in the earlier part of that window. Getting vaccinated during this period allows protective antibodies to pass to the baby before birth.
Warning Signs to Watch For
While the second trimester is generally the most comfortable phase of pregnancy, certain symptoms require immediate medical attention. A headache that won’t go away, feels like the worst of your life, or comes with blurred vision can signal dangerously high blood pressure. The same applies to sudden, extreme swelling of the hands or face, especially if your fingers are hard to bend or your eyes look puffy.
Vision changes like flashes of light, blind spots, or sudden blurriness are also red flags. So are chest pain, a fast or irregular heartbeat, trouble breathing, and a fever of 100.4°F (38°C) or higher. Severe belly pain that comes on suddenly, gets worse over time, or feels like sharp stabbing or cramping warrants urgent evaluation.
As your baby becomes more active in the second half of this trimester, pay attention to movement patterns. If you notice that your baby has stopped moving or is moving significantly less than usual, that’s a reason to seek care right away.