Welcome to the second trimester

The second trimester spans week 13 to week 28 of pregnancy, the middle 16 weeks of your journey. For most expectant parents, this stretch is widely considered the most physically comfortable period of the entire 40 weeks. Intense morning sickness and constant exhaustion typically begin to recede around week 14, a welcome surge of energy returns, and your bump becomes visible. Knowing what to expect in the second trimester brings a lot of reassurance, which is exactly why this phase is called the "honeymoon period" of pregnancy.

Want to know exactly where you stand in your timeline? The August AI Pregnancy Calculator tracks your current week, calculates your upcoming milestone windows, and helps you organize key clinical appointments.

Your body week by week

As your second trimester advances, your body progresses through three distinct phases:

  • Weeks 13 to 16 (the relief phase). Early pregnancy nausea and food aversions typically fade. As your energy climbs, the uterus rises up out of the pelvis. This shifting position gives you temporary relief from frequent urination by easing direct pressure on your bladder.
  • Weeks 17 to 20 (the visibility phase). Your baby bump becomes distinctly obvious to those around you. It's also during this window, typically between weeks 18 and 22, that you'll feel the very first flutters of fetal movement, a milestone known as "quickening." Your 20-week anatomy ultrasound also takes place during this timeframe.
  • Weeks 21 to 28 (the active phase). Fetal movements transform from soft flutters into distinct, coordinated kicks and rolls. As your center of gravity shifts to balance the growing bump, you may experience mild lower back strain, nighttime leg cramps, and occasional, erratic Braxton Hicks contractions.

By the time you reach the close of the second trimester, your expanding uterus will sit well above your navel, and a typical, healthy weight gain progresses to between 12 and 18 pounds. Tracking data from the Cleveland Clinic and Tommy's emphasizes that these shifts are standard signs of a healthy pregnancy.

Common second trimester symptoms

Your daily physical profile changes a lot as you transition out of the first trimester. The most common second trimester symptoms are driven by structural growth and shifting vascular demands:

  • Round ligament pain. Brief, sharp jabbing sensations or dull pulls in the lower abdomen or groin, triggered when the supportive ligaments stretch to accommodate the expanding uterus.
  • Backaches. Persistent muscular tension in the lower back, caused by your body adjusting its posture to counteract your front-heavy profile.
  • Nighttime leg cramps. Sudden, painful involuntary muscle contractions that primarily strike the calves during rest.
  • Heartburn. Elevated pregnancy hormones relax the muscular valve separating the stomach and esophagus, allowing gastric juices to creep upward.
  • Nasal congestion. Surging blood flow causes the delicate tissue inside the nasal passages to swell, mimicking a mild cold.
  • Skin changes. Marked by the famous "pregnancy glow," the darkening of the vertical linea nigra running down your belly, or patchy facial hyperpigmentation called melasma.
  • Mild swelling. Mild fluid retention causing soft swelling around the feet, ankles, and hands toward the end of the trimester.
  • Braxton Hicks contractions. Sporadic, painless practice tightenings of the uterus that come and go without a regular pattern.

According to the Cleveland Clinic and Sunflower Motherhood, gentle movement and staying hydrated are effective ways to keep these symptoms manageable.

Your baby's development

Inside the womb, fetal development in the second trimester moves at a remarkable pace. Your baby grows rapidly, transitioning from a delicate 3-inch embryo to an active, fully formed fetus measuring over 14 inches long.

  • Weeks 13 to 16. Fine facial features become distinct, and the baby begins practicing early sucking and swallowing motions. Tiny, permanent fingerprints take shape on the fingertips.
  • Weeks 17 to 20. The internal structures of the ear harden, allowing the baby to process and respond to external sounds like your voice. A protective layer of fine, downy hair called lanugo covers the skin, and this is typically when the baby moves noticeably enough for you to track.
  • Weeks 21 to 28. The complex air sacs inside the lungs develop at an accelerated rate. Your baby steadily packs on fat layers, safely crossing the major clinical threshold of week 24 viability, meaning the infant could potentially survive outside the womb with specialized neonatal intensive care.

By the time you reach the end of week 28, your baby weighs roughly 2 to 2.5 pounds, with active sleep cycles and fully functional sensory pathways, as confirmed by specialists at the Cleveland Clinic and Monica and Andy.

The 20-week ultrasound (anatomy scan)

The 20-week ultrasound, clinically referred to as the anatomy scan or mid-pregnancy ultrasound, is widely known as the most detailed scan of your entire pregnancy. Typically scheduled by your care team between weeks 18 and 22, this session takes roughly 30 to 45 minutes to complete.

During the procedure, a sonographer evaluates your baby's structural growth by tracking:

  • Major organ systems. Detailed views mapping out the heart chambers, brain symmetry, kidneys, and spine alignment.
  • Skeletal development. Verifying healthy bone development and measuring limb growth percentiles.
  • Gestational support. Checking the exact positioning of the placenta and tracking total amniotic fluid volumes.
  • Anatomical milestones. This is exactly when you find out the baby's sex, if you choose to have that information shared.

According to guidelines from BSW Health and the Cleveland Clinic, most parents leave the scan with printed images and significantly more clarity about how their pregnancy is progressing. Diagnostic findings during the scan, while uncommon, allow planning for any specialized care.

For more on the 20-week ultrasound, see BSW Health and Cleveland Clinic.

Second trimester checklist

Organizing your medical appointments and lifestyle adjustments during this comfortable window keeps your momentum moving smoothly. Build your routine around this second trimester checklist:

  • Book your anatomy scan. Make sure your detailed mid-pregnancy ultrasound is scheduled between weeks 18 and 22.
  • Screen for gestational diabetes. Undergo your routine glucose screening, typically timed between weeks 24 and 28.
  • Maintain supplementation. Continue taking daily prenatal vitamins rich in folic acid, iron, and DHA to support rapid fetal brain development.
  • Prioritize pelvic health. Start regular pelvic floor exercises (such as daily Kegels) to preserve bladder function postpartum.
  • Optimize your rest. Practice sleeping on your left side to maximize blood flow and nutrient delivery to the placenta.
  • Keep moving safely. Aim for roughly 30 minutes of low-impact, moderate exercise most days of the week.

Trying to stay ahead of your upcoming tests and milestones? The August AI Pregnancy Calculator maps out your gestational timeline, tracking your weekly milestones and key appointments automatically.

When to see a doctor

While the second trimester is typically a smooth, comfortable stretch, contact your doctor immediately if you notice warning signs such as second trimester bleeding, severe abdominal pain, decreased fetal movement after your 20th week, or fluid leaking from the vagina.

Preeclampsia emergency signs: seek immediate emergency care for sudden swelling in your face or hands accompanied by severe headaches or vision changes, which are critical signs of preeclampsia.

For a complete look at your entire prenatal road map, see pregnancy week by week: the complete guide to all 40 weeks, or the first trimester: your complete guide to weeks 1 to 13.