Second Trimester Guide: Weeks 14–27 — What to Expect

The second trimester spans weeks 14 through 27, and for many pregnant people it brings a noticeable shift in how they feel. The exhaustion and nausea of the first trimester typically begin to ease, energy returns, and the pregnancy often becomes visibly apparent to others. For the baby, this trimester involves extraordinary development — from a being a few centimetres long to one capable, in the later weeks, of surviving outside the womb with medical support.

This guide walks through what is happening for both the baby and the pregnant person, explains the key antenatal appointments and scans, and covers what to prepare for in the coming weeks.

Fact-Checked & Transparent: This article is fact-checked against current CDC, WHO, ACOG, and NHS guidelines. All health information is based on authoritative medical sources. Last verified: June 2026.

⚠️ MEDICAL DISCLAIMER

This article is educational information only. It is NOT a substitute for professional medical advice, diagnosis, or treatment.

Always consult your pediatrician or healthcare provider before making any medical decisions for your baby or child. Every baby is unique, and professional medical guidance is essential.

In case of emergency, call 911 or your local emergency number.

Baby Development: Weeks 14–16

At the start of the second trimester, the baby is approximately 9 cm long and weighs around 30 grams. Over the next three weeks, growth is rapid.

By week 14, the baby's facial features are becoming more defined and the neck is longer, meaning the head no longer rests directly on the chest. The baby begins making breathing movements — inhaling and exhaling amniotic fluid — which exercises the lungs long before they are needed for air.

Vernix caseosa — the waxy, white coating that protects the baby's skin from constant immersion in amniotic fluid — begins developing around week 16. Alongside this, lanugo (fine, downy hair) appears all over the body and helps the vernix adhere to the skin.

The baby begins swallowing amniotic fluid in earnest from around week 16 and producing urine, which is excreted back into the amniotic fluid. This cycle of swallowing and urinating is important for kidney and lung development.

From around week 16, the sex of the baby may be visible on ultrasound, though this depends on fetal positioning. In the UK, NHS sonographers do not routinely report the sex during the anatomy scan, though some parents learn it at private scans.

Baby Development: Weeks 17–20

This is the period of the anomaly scan — also called the anatomy scan — typically offered between weeks 18 and 21 in the NHS. In the weeks leading up to it, the baby's development continues rapidly.

By week 18, the ears are in their final position and the baby can begin to detect sound. Research suggests that by 18–20 weeks, babies respond to sounds from outside the womb, including voices.

The baby's movements become stronger and more purposeful during these weeks. Many pregnant people feel the first sensations of fetal movement — known as quickening — somewhere between weeks 16 and 20. First-time parents often notice it later than those who have been pregnant before, as it can be mistaken for digestive movement initially.

By week 20, the baby is approximately 25–26 cm long from crown to heel and weighs around 300 grams.

The Anomaly Scan: What Is Checked

The anomaly scan is one of the most significant appointments in the antenatal calendar. It is offered between 18 and 21 weeks and takes a detailed look at the baby's anatomy and the structures supporting the pregnancy.

The sonographer systematically examines:

The brain — checking for normal structure and ruling out conditions such as hydrocephalus (excess fluid) or anencephaly.

The face — looking at the lip and palate for cleft abnormalities where visible.

The heart — examining the four chambers, the outflow tracts, and checking for major structural abnormalities. Congenital heart defects are among the most common birth anomalies and the scan can identify many, though not all, of them.

The spine — checking that the vertebrae are all present and the skin over the spine is intact, which helps to identify neural tube defects such as spina bifida.

The kidneys and abdomen — confirming both kidneys are present and looking for abdominal wall defects.

The limbs — checking for normal structure and length.

The placenta — confirming its position. If the placenta is found to cover or partially cover the cervix (placenta praevia), a further scan later in pregnancy will be arranged to check whether it has moved upward as the uterus grows.

The umbilical cord — confirming it has the normal three vessels.

Amniotic fluid volume — too little or too much can indicate problems.

What the Anomaly Scan Cannot Guarantee

The scan is detailed and offered to every pregnant person in the NHS, but it is important to understand its limitations. It cannot detect every condition, and some abnormalities are only apparent after birth. The detection rates for specific conditions vary. The NHS publishes these detection rates: for example, the scan detects around 50% of heart defects — a meaningful number but far from complete coverage.

A normal anomaly scan is strongly reassuring but is not an absolute guarantee of a healthy baby.

Soft Markers

Sometimes the sonographer identifies what are called "soft markers" — features that are not abnormalities themselves but that are slightly more common in babies with chromosomal conditions such as Down's syndrome. Examples include a bright spot in the heart (echogenic intracardiac focus), slightly shortened limb bones, or excess fluid at the base of the neck.

A soft marker found in isolation, in a pregnancy with a low combined screening risk, generally does not change the overall risk significantly. Your sonographer and midwife will explain what any finding means in the context of your specific test results, and a referral to a fetal medicine unit for further assessment may be offered.

Baby Development: Weeks 21–27

The final weeks of the second trimester see the baby grow from approximately 27 cm to 35 cm in length, with weight increasing from around 360 grams to approximately 900 grams by week 27.

Hearing develops further, and by week 24–25 the baby's inner ear is functioning. Research referenced by the NHS indicates that babies can hear and react to sounds in the environment from around this stage.

The skin at this point is translucent and wrinkled, covered in vernix and lanugo. The baby's eyes are fused shut until around week 26–27, when the eyelids begin to open.

Week 24 is the viability threshold. This is the gestational age at which babies born prematurely have a reasonable chance of survival with intensive neonatal support. The NHS defines 24 weeks as the threshold from which active resuscitation is attempted. Survival rates improve significantly with each additional week of gestation beyond this point. At 24 weeks, survival rates are approximately 40–50%; by 27 weeks they are closer to 90%.

Changes in the Pregnant Person's Body

Energy and Nausea

The shift many people experience between weeks 12 and 16 is why the second trimester is often called the "honeymoon trimester." Nausea tends to resolve, sleep often improves, and energy returns. This is a good period to complete tasks that require sustained concentration or physical effort — antenatal classes, organising the nursery, longer social engagements — before the physical demands of the third trimester arrive.

Not everyone experiences this relief. A proportion of pregnant people continue to have nausea well into the second trimester, and some experience it throughout pregnancy. If nausea is still significantly affecting your quality of life at 14 weeks and beyond, speak with your midwife. Medication options are available.

The Bump Becomes Visible

The uterus rises above the pelvic brim at around 12 weeks, and by weeks 16–20 a visible bump is apparent for most people. First-time parents typically show later than those who have been pregnant before, as the abdominal muscles are less stretched. Bump size varies considerably between individuals and is not a reliable indicator of how the pregnancy is progressing — growth scans are used to assess this properly.

Round Ligament Pain

The round ligaments support the uterus and, as it grows, they are placed under increasing tension. This can cause sharp, stabbing or aching pain in the lower abdomen and groin, often triggered by sudden movement, rolling over in bed, or coughing. It is one of the most common causes of abdominal pain in the second trimester and is not dangerous, though it can be uncomfortable. Rest usually resolves it quickly.

If abdominal pain is persistent, severe, accompanied by bleeding, fever, or painful urination, seek medical attention rather than attributing it to round ligament pain.

Linea Nigra

A dark vertical line running down the centre of the abdomen — the linea nigra — often becomes visible during the second trimester. It is caused by increased melanin production driven by pregnancy hormones. It typically fades in the months after delivery.

Skin Changes

Many pregnant people notice changes to skin texture, pigmentation, and the appearance of stretch marks during the second trimester. Stretch marks appear as the skin on the abdomen, breasts, hips, and thighs is placed under increasing tension. They are influenced significantly by genetics — there is limited evidence that creams or oils prevent them, though keeping the skin moisturised may reduce itchiness.

Increased vaginal discharge — typically white or clear and without odour — is normal during pregnancy due to increased oestrogen and blood flow to the vaginal area. If discharge becomes yellow, green, foul-smelling, or is accompanied by itching or burning, speak with your GP as this may indicate infection.

Heartburn

The hormone progesterone relaxes smooth muscle throughout the body — including the lower oesophageal sphincter, which normally keeps stomach acid from rising into the oesophagus. Combined with the growing uterus placing pressure on the stomach from below, heartburn becomes increasingly common from the second trimester. Eating smaller meals more frequently, avoiding lying down immediately after eating, and sleeping with the head slightly elevated can all help. If heartburn is severe, speak with your GP — several over-the-counter and prescription treatments are considered safe in pregnancy.

Leg Cramps and Varicose Veins

Leg cramps — often occurring at night — are common from mid-pregnancy onwards. The cause is not fully established. Staying well hydrated and stretching the calf muscles before bed may help. Magnesium supplements are sometimes recommended but should be discussed with your midwife before taking.

Varicose veins are common in pregnancy due to increased blood volume and the pressure of the uterus on the pelvic veins. Compression stockings can reduce discomfort and are safe in pregnancy.

Antenatal Appointments in the Second Trimester

The NHS antenatal care schedule includes several key contacts during the second trimester:

16-week appointment: A midwife appointment to discuss the results of any first-trimester screening tests, review symptoms, check blood pressure, and offer information and support. Blood tests may be repeated if not completed earlier.

18–21 week anomaly scan: The anatomy scan described above, offered at an NHS scanning unit.

25-week appointment (for first-time parents): A midwife appointment that includes blood pressure measurement, urine testing, and checking the size of the uterus. For those who have been pregnant before, the 25-week appointment is not always included in the standard schedule.

The Glucose Tolerance Test

Between weeks 24 and 28, a glucose tolerance test (GTT) is offered to pregnant people at increased risk of gestational diabetes. Risk factors include a pre-pregnancy BMI above 30, a previous pregnancy affected by gestational diabetes, a family history of type 2 diabetes, and South Asian, Black African, or Middle Eastern ethnicity.

The GTT involves a fasting blood test, a glucose drink, and a second blood test two hours later. If the results indicate gestational diabetes, dietary changes and — in some cases — medication will be discussed by a specialist diabetes and maternity team.

Mental Health in the Second Trimester

While many people feel emotionally better in the second trimester compared to the first, this is not universal. Antenatal anxiety and depression can emerge or persist throughout pregnancy. The results of the anomaly scan — including when soft markers are identified or conditions are detected — can trigger significant anxiety.

The NHS now routinely screens for anxiety and depression at antenatal appointments. If you are struggling with persistent worry, low mood, difficulty sleeping unrelated to physical symptoms, or loss of pleasure in activities, tell your midwife. Perinatal mental health support is available through most NHS trusts.

Preparing for the Third Trimester

The second trimester is a good time to begin preparations that will help the final weeks feel more manageable:

Antenatal classes: Many NHS trusts offer free antenatal education, and independent courses (such as NCT classes) are also available. Booking in the second trimester ensures a place on courses that often fill up. Classes cover labour, pain relief, infant feeding, and caring for a newborn.

Birth preferences: Starting to think about and document your preferences for labour and delivery — including preferred pain relief, position preferences, and what you want to happen if things don't go to plan — gives you time to discuss them thoroughly with your midwife.

Practical preparations: Organising the nursery, washing newborn clothing, and researching feeding options are manageable in the second trimester in a way that often feels harder in the third.

Frequently Asked Questions

When should I start feeling the baby move?

Most first-time parents notice fetal movement between weeks 18 and 20, though some feel it as early as 16 weeks. Those who have been pregnant before may notice movement earlier. From around 24 weeks, you should be aware of a regular pattern of movement. Any reduction in what is normal for your baby from 24 weeks onwards should be reported to your midwife or maternity unit promptly.

What is the anatomy scan looking for and do I need to worry before it?

The anomaly scan systematically checks the baby's organs, brain, spine, heart, and limbs, and the position of the placenta. The majority of scans show everything is developing normally. While it is natural to feel anxious beforehand, most people leave the scan reassured. If something is found, your sonographer will explain what it means and what happens next.

Is round ligament pain normal?

Yes. Sharp, stabbing pains in the lower abdomen and groin, particularly on sudden movement, are very commonly caused by round ligament tension as the uterus grows. Rest usually provides quick relief. Persistent, severe, or unusual pain should always be assessed by a midwife.

What does it mean if the placenta is low at the 20-week scan?

A low-lying placenta at 20 weeks — covering or near the cervix — does not necessarily mean there is a problem with the pregnancy. Many placentas that appear low at 20 weeks move upward as the uterus grows. A follow-up scan at around 32–34 weeks checks whether the placenta has moved sufficiently away from the cervix.

Can I exercise during the second trimester?

The NHS advises that most forms of moderate exercise are safe and beneficial during the second trimester. Aim for around 150 minutes of moderate activity per week, such as walking, swimming, or pregnancy yoga. Avoid lying flat on your back for exercise after 28 weeks, and contact sports or high-impact activities that risk abdominal injury. Always discuss exercise plans with your midwife if you have any complications.

When should antenatal classes be booked?

Ideally during the second trimester. Classes are often scheduled to begin around 28–32 weeks, but popular courses fill up quickly. Book NCT or other independent courses as early as possible; NHS antenatal education is typically booked through your midwife.

Key Takeaways

• The second trimester (weeks 14–27) is often the most physically comfortable period of pregnancy, as nausea typically eases and energy returns
• The baby grows from approximately 9 cm to 35 cm during these weeks, developing hearing, swallowing, and response to external stimuli
• The anomaly scan at 18–21 weeks checks all major organ systems and placenta position — a normal scan is reassuring but cannot rule out every condition
• Week 24 is the viability threshold: babies born from this point have a chance of survival with neonatal intensive care
• The glucose tolerance test is offered between 24 and 28 weeks to those at risk of gestational diabetes
• Antenatal anxiety and depression can occur in the second trimester — tell your midwife if your mental health is a concern, as support is available

📋 SOURCES & FACT-CHECKING

This article is compiled and verified against these authoritative sources: - CDC (Centers for Disease Control & Prevention) - WHO (World Health Organization) - ACOG (American College of Obstetricians and Gynecologists) - NHS (National Health Service) - AAP (American Academy of Pediatrics)

Last verified: June 2026

Educational content only. Always consult your pediatrician for medical decisions.

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