The second trimester spans weeks 14 through 27 and is often called the most comfortable phase of pregnancy. Morning sickness typically fades, energy returns, and the baby grows from the size of a lemon to over 36 cm (14 inches) in length. By the end of the second trimester, your baby can hear your voice, open their eyes, and respond to light. This guide covers what happens each month, key milestones, and what to expect at your prenatal appointments.
Key Takeaways
- The second trimester runs from week 14 through week 27 (approximately months 4–6)
- Most people feel the baby's first movements (quickening) between weeks 16 and 22
- The anatomy scan (mid-pregnancy ultrasound) is typically done between weeks 18 and 22
- The glucose screening test for gestational diabetes is done between weeks 24 and 28
- Energy usually returns and morning sickness fades, making this the most comfortable trimester for many
Month 4: Weeks 14–17
The transition from first to second trimester often brings welcome relief.
What's happening:
- Week 14: The baby is about 8.7 cm and weighs 43 grams. Facial features are becoming more defined — the eyes have moved closer together, and the ears are nearly in their final position.
- Week 15: The baby is making active movements — flexing arms and legs, making fists, and sucking the thumb. The skeleton is developing from cartilage into bone.
- Week 16: Quickening may begin — first-time mothers often feel this closer to weeks 18–22, while those who have been pregnant before may notice it earlier. The baby is about 11.6 cm and weighs 100 grams.
- Week 17: Fat stores begin to develop under the skin. The baby's hearing is developing, though the inner ear structures aren't fully formed yet.
Common symptoms: Increased energy, reduced nausea, growing belly becoming visible, nasal congestion, round ligament pain (sharp pains in the lower abdomen from the stretching uterus).
Month 5: Weeks 18–22
This is the month of the anatomy scan and, for many, the first unmistakable baby kicks.
What's happening:
- Week 18: The baby is about 14.2 cm and can yawn, hiccup, and swallow amniotic fluid. The nervous system is maturing rapidly.
- Week 19: A waxy coating called vernix caseosa begins to cover the skin, protecting it from the amniotic fluid.
- Week 20: The halfway point. The baby measures about 25 cm from head to heel and weighs around 300 grams. You may be able to find out the sex at the anatomy scan.
- Week 21: The baby's movements become stronger and more coordinated. Eyebrows and eyelashes are forming.
- Week 22: The baby weighs about 430 grams. The lungs are developing but are not yet mature enough for breathing air. The brain is developing rapidly.
The anatomy scan (weeks 18–22): This detailed ultrasound checks the baby's organs, limbs, spine, brain, heart, placenta position, and amniotic fluid levels. It's the most comprehensive scan of the pregnancy and typically takes 30–45 minutes.
Common symptoms: Baby kicks, back pain, leg cramps (especially at night), skin changes (linea nigra, darkening of nipples), increased appetite.
Month 6: Weeks 23–27
Your baby is gaining weight and developing the systems needed for life outside the womb.
What's happening:
- Week 23: The baby weighs about 500 grams. The lungs are producing surfactant, a substance that will help them inflate after birth.
- Week 24: The viability milestone — with intensive neonatal care, babies born at 24 weeks have a survival rate of approximately 40–70%, improving each day.
- Week 25: The baby responds to sound. Loud noises may cause a startle reflex. The brain is developing its characteristic folds.
- Week 26: The eyes open for the first time. The baby can detect light and dark. Read our detailed week 26 guide for more.
- Week 27: The last week of the second trimester. The baby weighs about 875 grams and measures 36.6 cm. The brain is very active, and regular sleep-wake cycles are establishing.
Common symptoms: Braxton Hicks contractions, shortness of breath, swelling in hands and feet, trouble sleeping, itchy belly skin, back pain.
Key Prenatal Appointments
| When | What |
|---|---|
| Weeks 18–22 | Anatomy scan (detailed ultrasound) |
| Every 4 weeks | Routine prenatal checkups (blood pressure, fundal height, urine, fetal heartbeat) |
| Weeks 24–28 | Glucose challenge test (GCT) for gestational diabetes screening |
| Week 24+ | Rhogam injection if Rh-negative |
| Ongoing | Blood pressure monitoring for preeclampsia signs |
Tips for the Second Trimester
- Start sleeping on your side — from mid-pregnancy onward, side sleeping (particularly left side) optimizes blood flow to the uterus. A pregnancy pillow makes this easier.
- Stay active — walking, swimming, and prenatal yoga are safe and beneficial for most pregnancies. Aim for 150 minutes of moderate activity per week (ACOG recommendation).
- Begin a birth plan — start thinking about your preferences for labor and delivery. Discuss options with your provider.
- Track fetal movement — once you're feeling regular kicks (usually by week 24–28), pay attention to patterns. Use our Milestone Tracker to log developments.
- Moisturize — it won't prevent stretch marks, but it helps with the intense itching from stretching skin.
- Plan ahead — register for childbirth classes, tour your birth facility, and start building your hospital bag checklist.
Frequently Asked Questions
When will I feel the baby move?
Most first-time mothers feel the baby's first movements (called quickening) between weeks 18 and 22. It often feels like fluttering, bubbles, or gentle tapping. Those who have been pregnant before may feel movement as early as week 16. By week 24–28, movements should be consistent and daily.
What happens during the anatomy scan?
The anatomy scan (also called the mid-pregnancy ultrasound or anomaly scan) is a detailed ultrasound usually done between weeks 18 and 22. The sonographer checks the baby's brain, heart, spine, limbs, organs, placenta position, amniotic fluid levels, and umbilical cord. You can usually find out the sex of the baby at this scan if you wish to know.
When is the glucose test done during pregnancy?
The glucose challenge test (GCT) for gestational diabetes screening is typically done between weeks 24 and 28. You drink a glucose solution and have your blood drawn one hour later. If your levels are elevated, a follow-up 3-hour glucose tolerance test is done to confirm or rule out gestational diabetes.
Is it normal to have Braxton Hicks contractions in the second trimester?
Yes. Braxton Hicks contractions (practice contractions) can begin as early as the second trimester, though many people don't notice them until the third trimester. They are irregular, usually painless, and stop when you change position or rest. If contractions become regular, painful, or are accompanied by other symptoms, contact your provider.
How much weight should I gain in the second trimester?
For people with a normal pre-pregnancy BMI, the general guideline is about 0.5 kg (1 lb) per week during the second and third trimesters, for a total pregnancy weight gain of 11.5–16 kg (25–35 lbs). Your provider will track your weight at each appointment and advise you based on your individual situation.