The second trimester of pregnancy spans from week 14 through week 27. It covers the middle three months and is often called the most comfortable stretch of pregnancy, as early symptoms like nausea and fatigue tend to fade while the baby undergoes rapid growth and development.
When It Starts and Ends
The American College of Obstetricians and Gynecologists defines the second trimester as 14 weeks and 0 days through 27 weeks and 6 days. That roughly translates to months four, five, and six. By the start of this trimester, the placenta is fully functional and takes over hormone production, which is why many of the rough first-trimester symptoms ease up.
How Your Baby Develops
The second trimester is a period of dramatic change. Your baby goes from about the size of a lemon to nearly two pounds, and nearly every organ system comes online during these 14 weeks.
Weeks 14 to 18
Red blood cells begin forming in the spleen around week 14, and the scalp hair pattern starts taking shape by week 15. By week 16, the eyes can move slowly and the ears are nearly in their final position. At week 18, the digestive system starts working, and your baby may begin to hear sounds for the first time as the ears start standing out from the head.
Weeks 19 to 22
Around week 19, your baby begins releasing urine that makes up most of the amniotic fluid. By week 20, your baby has regular sleep-wake cycles and can be woken by noises or your movements. A fine, downy hair called lanugo covers the entire body by week 21, helping hold a protective waxy coating on the skin. Eyebrows and hair become visible by week 22.
Weeks 23 to 27
The lungs begin producing surfactant around week 23, a substance that will eventually allow the air sacs to inflate properly after birth. Rapid eye movements also begin around this time. By week 25, your baby may move in response to familiar sounds like your voice. Eyebrows and eyelashes are fully formed by week 26, though the eyes may not open for another couple of weeks.
Feeling Your Baby Move
One of the hallmarks of the second trimester is quickening, the first time you feel your baby move. This typically happens between 16 and 20 weeks. If you’ve been pregnant before, you may notice it closer to 16 weeks. First-time mothers often don’t feel movement until around 20 weeks. Most women describe the sensation as bubbles popping or light tapping, and it can be easy to mistake for gas at first. Over the following weeks, those flutters become unmistakable kicks and rolls.
Physical Changes You Can Expect
While the nausea of the first trimester usually fades, the second trimester brings its own set of body changes as your uterus grows and hormone levels continue rising.
Skin changes are common. Increased melanin production can cause brown, tan, or gray patches on your face, a condition called melasma. Many women also notice a dark vertical line running down the belly, known as linea nigra. Both are harmless and typically fade after delivery.
Nasal congestion and nosebleeds catch many women off guard. Rising hormone levels increase blood volume, which can make the lining of your nose swell and bleed more easily. A stuffy nose that lasts for weeks without any cold symptoms is a classic second-trimester experience. A humidifier and saline spray can help.
Round ligament pain is another frequent complaint. As the uterus expands, the ligaments supporting it stretch, causing sharp or aching pains on one or both sides of the lower belly, especially with sudden movements like standing up or rolling over in bed.
Key Tests and Screenings
The Anatomy Scan
The 20-week ultrasound, sometimes called the anatomy scan, is the most detailed imaging appointment of pregnancy. A sonographer takes pictures and measurements of your baby’s heart, brain, spine, kidneys, bladder, arms, legs, hands, feet, fingers, toes, facial features, chest, lungs, stomach, and intestines. They also record the heart rate, check blood flow through the umbilical cord, note where the placenta is positioned, measure the amount of amniotic fluid, and examine your cervix. This is also the appointment where you can find out the sex if you want to know.
Glucose Screening
Between 24 and 28 weeks, most women are screened for gestational diabetes with a glucose challenge test. You drink a sugary solution and have your blood drawn an hour later. A blood sugar level below 140 mg/dL is considered normal. A result between 140 and 189 mg/dL means you’ll need a longer follow-up test to confirm whether gestational diabetes is present. A result of 190 mg/dL or higher indicates gestational diabetes. Some clinics use a lower cutoff of 130 mg/dL, so your provider may interpret results slightly differently.
Nutrition and Weight Gain
Calorie needs increase modestly during pregnancy. The general recommendation is about 300 extra calories per day, roughly the equivalent of a handful of nuts with a piece of fruit and some yogurt. The second trimester is when most women start gaining weight more noticeably, typically around one pound per week, though the target varies based on your pre-pregnancy weight. Iron, calcium, and folate remain especially important as your baby’s bones strengthen and blood volume expands.
Braxton Hicks Contractions
Some women begin feeling Braxton Hicks contractions during the second trimester. These are practice contractions that are irregular, unpredictable, and more uncomfortable than truly painful. They may last anywhere from less than 30 seconds to about 2 minutes, and they often stop if you change positions or activity levels.
True labor contractions are different in several specific ways. They come at regular intervals and get closer together over time. They last 30 to 90 seconds and grow longer. They get stronger rather than staying the same or fading. They typically start in the mid-back and wrap around to the front of the abdomen, rather than being felt in just one spot. And they continue regardless of movement or position changes. If your contractions follow this pattern before 37 weeks, it could signal preterm labor and warrants prompt medical attention.