Pregnancy week 20 is a major milestone: you are approximately halfway through a typical 40-week pregnancy.

The fetus is becoming increasingly active and recognizable. Hearing is developing, the digestive system is functioning, movements are stronger, and a protective creamy coating called vernix caseosa is beginning to cover the skin.

For many pregnant people, week 20 is also when the detailed mid-pregnancy anatomy scan takes place. This ultrasound examines many fetal structures and also provides information about the placenta, amniotic fluid, fetal growth and movement.

Quick answer: At 20 weeks pregnant, the fetus is around 25.6 cm from head to heel according to NHS guidance—approximately the length of a banana. Movement may feel more obvious, vernix is covering the skin, thumb-sucking may occur, and many pregnancies have their detailed anatomy ultrasound around this stage.

What Does 20 Weeks Pregnant Mean?

Pregnancy is dated from the first day of the last menstrual period (LMP) rather than from the day of conception.

At 20 weeks pregnant, conception usually occurred about 18 weeks earlier in a typical menstrual cycle.

You remain in the second trimester.

Week 20 is often described as the halfway point because pregnancy dating commonly uses a 40-week estimated duration.

However, your due date remains an estimate, not an exact prediction of the day birth will occur.

Are You Exactly Halfway Through Pregnancy at 20 Weeks?

In pregnancy dating terms, approximately yes.

A due date is usually calculated around 40 weeks from the first day of the LMP.

So reaching week 20 means that around half of those 40 gestational weeks have passed.

That does not mean exactly half of fetal growth is complete.

Much of the fetus’s:

• weight gain;
• brain maturation;
• lung development;
• fat storage;

still happens later in pregnancy.

How Big Is the Baby at 20 Weeks?

The NHS estimates the fetus at around 25.6 cm long from head to heel at week 20.

This is approximately the length of a banana.

ACOG separately notes that by the end of week 20, the fetus is more than 6 inches long and weighs less than 11 ounces.

Differences in published measurements can occur because organizations may use different:

• measurement conventions;
• reference charts;
• points within a gestational week.

Individual ultrasound measurements are more useful than fruit comparisons.

Why Does Measurement Change at Week 20?

Earlier in pregnancy, fetal length is commonly described from the head to the bottom, or crown-rump length, because the legs are curled and difficult to measure consistently.

The NHS notes that from around week 20, measurements are presented from head to heel instead.

That explains why the reported length suddenly appears much larger compared with previous weeks.

It does not mean the fetus doubled in size in only one week.

What Is Developing at 20 Weeks Pregnant?

ACOG groups weeks 17–20 together as a period when:

• hearing is developing;
• the brain region controlling movement is well developed;
• the digestive system is working;
• facial features become more recognizable;
• lanugo begins covering the body.

By the end of week 20, fetal size and movement have increased considerably.

Week 20 also introduces another important protective development: vernix caseosa.

What Is Vernix Caseosa?

Vernix caseosa is a white, creamy or greasy substance that forms over fetal skin.

The NHS notes that the fetus is covered in this protective layer around week 20.

Vernix helps protect delicate fetal skin while it remains immersed in amniotic fluid.

Without protection, prolonged exposure to fluid could affect developing skin.

What Is Vernix Made Of?

Vernix is made from a mixture of substances including:

• skin cells;
• oils from fetal skin glands;
• water;
• proteins and lipids.

Its composition changes as pregnancy progresses.

It forms a protective barrier over fetal skin.

Does Vernix Have a Purpose During Birth?

The NHS notes that this slippery coating may also help during passage through the birth canal.

Vernix can still be present on newborn skin after delivery, particularly when birth occurs before it has mostly disappeared.

Is Lanugo Still Present at Week 20?

Yes.

Lanugo is the fine, soft hair covering much of the fetal body.

ACOG notes that lanugo develops across the body during weeks 17–20.

Lanugo and vernix work together as part of the developing skin environment.

Most lanugo disappears later in pregnancy, although some newborns still have small amounts.

What Is the Baby’s Skin Like at Week 20?

Fetal skin is still:

• thin;
• delicate;
• developing.

There is not yet the amount of subcutaneous fat that will accumulate later in pregnancy.

Vernix provides protection while the skin continues maturing.

During the third trimester, increasing fat deposits help give fetal skin a smoother and fuller appearance.

Is the Baby Moving More at 20 Weeks?

Yes.

The NHS describes the fetus as becoming more active each day.

Movement can include:

• kicking;
• punching;
• turning;
• stretching;
• rolling;
• moving hands toward the face.

As the fetus becomes larger and stronger, these movements can become easier to recognize.

Can You Feel the Baby Move at 20 Weeks?

Many people can by this stage.

Early movement may still feel like:

• fluttering;
• bubbling;
• gentle taps;
• rolling;
• small kicks.

However, movement timing varies between pregnancies.

People in a first pregnancy may recognize movement later than those who have previously been pregnant.

Placental position can also affect how strongly movement is felt.

Is It Normal Not to Feel Movement at 20 Weeks?

It can still be normal, particularly in a first pregnancy or when the placenta is positioned toward the front of the uterus.

Fetal movement does not begin on the same exact day for everyone.

If you are concerned about not feeling movement, discuss it with your maternity healthcare professional rather than comparing your pregnancy with another person’s.

Should You Start Counting Kicks at Week 20?

Usually, formal kick counting is not started this early.

At 20 weeks:

• movement can still be irregular;
• intensity varies;
• fetal position changes what you feel;
• patterns may not yet be predictable.

What matters now is gradually becoming familiar with fetal movement as it develops.

Later in pregnancy, awareness of your baby’s usual pattern becomes increasingly important.

Can the Baby Suck Its Thumb at 20 Weeks?

Yes.

The NHS notes that the fetus may suck its thumb at this stage.

Thumb-sucking is part of development of the sucking reflex, which will eventually be important for feeding after birth.

It requires coordination between:

• mouth muscles;
• tongue;
• jaw;
• nervous system.

Does Thumb-Sucking Mean the Baby Is Hungry?

No.

Thumb-sucking before birth is mainly a developmental reflex and movement pattern.

The fetus receives nutrients continuously through the placenta rather than becoming hungry between meals in the way a newborn does.

Can the Baby Swallow at Week 20?

Yes.

MedlinePlus describes weeks 19–21 as a period when the fetus can hear, moves actively and develops swallowing ability.

Swallowing amniotic fluid helps development of:

• mouth coordination;
• throat muscles;
• gastrointestinal function.

Is the Digestive System Working?

Yes, at a fetal developmental level.

ACOG notes that the digestive system is working during weeks 17–20.

However, nutrients still reach the fetus through the placenta.

The fetus is not digesting food in the same way a newborn does.

Can the Baby Hear at 20 Weeks?

Yes.

ACOG states that the fetus can hear sounds by week 18, so hearing is continuing to develop by week 20.

The fetus is exposed to sounds such as:

• maternal heartbeat;
• blood flow;
• digestive sounds;
• the pregnant person’s voice;
• external environmental sounds.

The sounds are filtered through maternal tissues and amniotic fluid.

Can the Baby Recognize Your Voice?

The auditory system is becoming increasingly functional, but voice recognition develops gradually.

It is reasonable to talk or sing normally.

There is no evidence-based need to play loud music directly against the abdomen.

Normal environmental sound is enough for developing hearing.

What Is Happening to the Brain?

Brain development remains rapid.

The motor-control regions are increasingly developed, helping produce more coordinated movements.

However, the fetal brain still has extensive development ahead.

Important later changes include maturation of:

• sensory systems;
• sleep cycles;
• cortical connections;
• memory-related networks;
• breathing regulation.

Are the Bones Stronger at 20 Weeks?

Yes.

The skeleton continues mineralizing and becoming more visible on ultrasound.

MedlinePlus ultrasound material shows that developing fetal bones appear bright on ultrasound images because of their increasing mineral content.

Bones continue growing throughout pregnancy and childhood.

What Happens at the 20-Week Anatomy Scan?

The mid-pregnancy anatomy scan is one of the most important routine prenatal ultrasounds.

ACOG recommends that all pregnant patients be offered a second-trimester ultrasound to look for fetal structural abnormalities, ideally between 18 and 22 weeks.

A standard ultrasound can assess:

• fetal physical development;
• fetal size;
• movement;
• heart rate;
• amniotic fluid;
• placenta location;
• number of fetuses.

Which Parts of the Baby Are Checked?

The sonographer may examine structures including the:

• brain;
• skull;
• face;
• spine;
• heart;
• abdomen;
• stomach;
• kidneys;
• bladder;
• arms;
• legs;
• hands;
• feet.

The exact examination follows local healthcare protocols.

Is the Heart Checked in Detail?

Yes.

The fetal heart is an important part of the anatomy examination.

The sonographer may assess:

• heart location;
• chambers;
• rhythm;
• major structures that are visible on standard ultrasound.

If a concern is found or there are specific risk factors, a more specialized fetal cardiac examination may be recommended.

Is the Spine Checked?

Yes.

The anatomy scan evaluates the fetal spine for visible structural development.

Ultrasound can identify some spinal abnormalities, but it cannot detect every possible problem.

Are the Brain and Head Checked?

Yes.

The ultrasound examines fetal head and brain anatomy that can be visualized at this gestational stage.

Measurements may also be taken to assess growth.

Are the Kidneys and Bladder Checked?

Usually, yes.

The urinary system is part of fetal structural assessment.

The presence and appearance of the:

• kidneys;
• bladder;

can provide useful information about fetal development.

Is the Placenta Checked?

Yes.

ACOG notes that standard ultrasound provides information about placenta location.

The placenta may be described as:

• anterior;
• posterior;
• fundal;
• low lying;

depending on where it is attached.

What Does a Low-Lying Placenta Mean?

A placenta described as low lying is positioned near the lower part of the uterus.

At 20 weeks, this does not necessarily mean it will remain low later in pregnancy.

As the uterus grows, the relationship between the placenta and cervix may change.

Your maternity team may schedule follow-up imaging when appropriate.

Is Amniotic Fluid Checked?

Yes.

A standard ultrasound can provide information about the amount of amniotic fluid.

Amniotic fluid is important because it:

• cushions the fetus;
• allows movement;
• supports lung development;
• protects the umbilical cord.

Can the Baby’s Sex Be Seen at the 20-Week Scan?

Often, yes—if the fetus is in a favorable position.

ACOG notes that sex may sometimes be identified during a standard ultrasound when fetal position allows.

However, sex determination is not the primary purpose of the anatomy scan.

What If You Do Not Want to Know the Sex?

Tell the sonographer before the examination begins.

Healthcare practices vary, but your preference can usually be respected.

What If the Sonographer Cannot See Everything?

This is common.

The fetus may be:

• facing the wrong direction;
• curled up;
• moving;
• covering important structures.

If the scan cannot obtain all required views, you may be asked to return for another ultrasound.

An incomplete examination does not automatically indicate an abnormality.

Can the Anatomy Scan Detect Every Birth Defect?

No.

This is an important limitation.

The anatomy scan can identify many structural abnormalities, but it cannot detect every:

• congenital anomaly;
• genetic condition;
• neurological condition;
• developmental disorder.

Some conditions develop later or cannot be visualized with ultrasound.

A normal anatomy scan is reassuring but does not guarantee a completely healthy pregnancy or newborn.

What If a Structural Abnormality Is Found?

If an abnormality is suspected, your healthcare provider may recommend:

• a repeat scan;
• detailed specialist ultrasound;
• maternal-fetal medicine consultation;
• genetic counseling;
• diagnostic testing.

ACOG recommends genetic counseling, diagnostic testing and comprehensive ultrasound evaluation when a fetal anomaly is identified.

A suspicious ultrasound finding is not always a final diagnosis.

What Is a Soft Marker?

A soft marker is an ultrasound finding that may also occur in healthy fetuses but can sometimes be associated with certain chromosome conditions.

ACOG advises interpreting isolated soft markers in combination with previous screening results and the individual pregnancy context.

A soft marker alone does not automatically mean the fetus has a genetic condition.

Is an Anatomy Scan Still Needed After Low-Risk NIPT?

Yes.

ACOG recommends structural ultrasound between 18 and 22 weeks for all patients, whether or not earlier chromosome screening was low risk.

NIPT and ultrasound evaluate different things.

NIPT mainly estimates risk for selected chromosome conditions.

The anatomy scan evaluates physical structures.

Can the Due Date Change After the 20-Week Scan?

Usually not if a reliable earlier dating ultrasound already established the estimated due date.

ACOG considers first-trimester ultrasound the most accurate method for establishing gestational age and advises that later changes to the estimated due date should be uncommon.

A fetus measuring slightly ahead or behind at 20 weeks does not automatically mean the due date is wrong.

What If You Never Had an Early Ultrasound?

The 20-week scan can still provide useful dating information.

However, ACOG considers pregnancies without ultrasound confirmation or revision of the estimated due date before 22 weeks to be suboptimally dated.

Your healthcare professional can determine the best clinical estimate.

What Is Happening in Your Body at 20 Weeks?

The uterus is now much larger than it was early in pregnancy.

You may notice:

• a clearly visible bump;
• stronger fetal movement;
• back discomfort;
• stretching sensations;
• heartburn;
• constipation;
• leg cramps;
• breast changes;
• skin changes.

The NHS also highlights calf cramps as a common week-20 complaint.

Why Do Leg Cramps Happen?

Leg cramps are sudden muscle spasms.

They often affect the calves and can wake you during the night.

The exact cause in pregnancy is not always clear.

Possible contributors may include:

• muscle fatigue;
• circulatory changes;
• altered body mechanics.

What Can Help a Calf Cramp?

The NHS suggests stretching the affected calf by pulling the toes upward toward the ankle.

Gentle daytime activity may also help some people.

Seek medical advice if one leg becomes persistently:

• swollen;
• red;
• warm;
• painful.

Those symptoms should not simply be assumed to be an ordinary cramp.

Is Back Pain Normal at 20 Weeks?

Mild back discomfort is common.

Contributors can include:

• larger uterus;
• changing posture;
• altered center of gravity;
• more flexible ligaments.

Helpful measures may include:

• supportive footwear;
• careful lifting;
• regular appropriate movement;
• good sitting posture.

Persistent or severe pain deserves professional assessment.

Is Round Ligament Pain Normal?

Yes.

As the uterus grows, supporting ligaments continue stretching.

This may cause:

• pulling;
• brief sharp pain;
• lower abdominal discomfort;
• groin discomfort.

Severe or persistent pain should not automatically be attributed to ligament stretching.

Is Heartburn Common?

Yes.

Pregnancy hormones relax digestive muscles, and the enlarging uterus changes abdominal pressure.

Helpful strategies can include:

• smaller meals;
• eating slowly;
• avoiding personal trigger foods;
• remaining upright after eating.

Ask a pharmacist or clinician before using unfamiliar medication.

Is Constipation Normal?

Yes.

Pregnancy hormones can slow bowel movement.

General strategies include:

• adequate water;
• dietary fiber;
• regular activity.

If iron supplements worsen constipation, discuss options with your clinician instead of stopping prescribed iron yourself.

Is Dizziness Still Possible?

Yes.

Circulatory changes can cause occasional dizziness.

Reduce risk by:

• standing slowly;
• staying hydrated;
• eating regularly;
• avoiding overheating.

Seek assessment for fainting or severe persistent dizziness.

Are Headaches Normal?

Mild headaches may occur.

Possible contributors include:

• dehydration;
• tiredness;
• stress;
• hormonal changes.

Seek medical advice for severe or persistent headaches, particularly when accompanied by:

• visual disturbances;
• significant swelling;
• feeling very unwell.

Is Swelling Normal?

Mild swelling of the hands or feet can develop during pregnancy.

The NHS lists swollen hands and feet among possible second-trimester symptoms.

Sudden or marked swelling should be discussed with a healthcare professional.

Are Stretch Marks Common?

Yes.

As the abdomen and breasts grow, stretch marks can appear.

They may look:

• pink;
• red;
• purple;
• brown;

depending on skin tone.

No cream can guarantee prevention, although moisturizers may help dryness or itching.

Is Vaginal Discharge Normal?

White or milky discharge can be normal.

Seek medical advice if discharge becomes:

• foul smelling;
• green or yellow;
• painful;
• itchy;
• associated with fever.

A sudden gush or persistent watery leakage should also be assessed.

What About Vaginal Bleeding?

Any pregnancy bleeding deserves attention.

Contact a healthcare professional for bleeding.

Seek urgent care for:

• heavy bleeding;
• severe abdominal pain;
• fainting;
• severe dizziness;
• worsening symptoms.

Can the Baby Survive if Born at 20 Weeks?

At 20 weeks, fetal organs—particularly the lungs—are still extremely immature.

This stage is far earlier than the gestational ages at which neonatal survival is ordinarily expected.

Because questions about extremely premature birth involve rapidly changing clinical circumstances and individualized neonatal care, they should be discussed with an obstetric and neonatal specialist rather than answered with a simple online survival percentage.

What Prenatal Appointments Happen Around Week 20?

The major event for many pregnancies is the anatomy ultrasound.

Other routine prenatal care may include:

• blood-pressure monitoring;
• urine testing;
• review of symptoms;
• fetal cardiac assessment;
• discussion of earlier screening results;
• planning later appointments.

Schedules vary by healthcare system.

Is Genetic Screening Finished by Week 20?

Many earlier chromosome-screening tests may already have been completed.

However, the anatomy ultrasound remains important because structural abnormalities can occur with or without chromosome abnormalities.

Your provider may recommend additional evaluation if a new ultrasound finding appears.

Can Amniocentesis Still Be Performed?

Amniocentesis is a diagnostic test that may be offered in certain circumstances after counseling.

It is not routinely required for every pregnancy.

Possible reasons for discussing diagnostic testing can include:

• high-risk screening results;
• certain ultrasound abnormalities;
• specific genetic concerns.

The decision should be made with a healthcare professional or genetics specialist.

What About Nutrition at 20 Weeks?

Balanced nutrition remains important because fetal and maternal tissue growth is accelerating.

Aim for appropriate sources of:

• protein;
• iron;
• calcium;
• iodine;
• vitamin D;
• folate;
• healthy fats;
• other micronutrients.

No individual food guarantees healthy fetal development.

Is Iron Particularly Important?

Yes.

Maternal blood volume continues to increase.

Iron is needed for hemoglobin production and oxygen transport.

Food sources include:

• lean meats;
• beans;
• lentils;
• fortified cereals;
• leafy green vegetables.

Some people need supplements according to blood-test results.

Is Calcium Important?

Yes.

Calcium contributes to developing:

• bones;
• teeth;
• muscles;
• nerves.

It also supports maternal bone health.

Sources may include:

• milk;
• yogurt;
• cheese;
• fortified plant alternatives;
• other calcium-rich foods.

Is Protein Important?

Yes.

Protein supports the growth of:

• fetal tissue;
• placenta;
• uterus;
• maternal tissues.

Aim for varied sources rather than relying on high-dose protein supplements unless medically advised.

Do You Need to Eat for Two?

No.

Pregnancy does not mean doubling food intake.

Energy needs increase gradually, but the goal should remain balanced, nutrient-rich nutrition rather than simply larger portions.

Can You Exercise at 20 Weeks?

Many people with uncomplicated pregnancies can continue moderate physical activity.

Examples may include:

• walking;
• swimming;
• prenatal exercise;
• moderate strength training;
• pregnancy-adapted yoga.

Your healthcare provider may recommend modifications depending on your medical history.

Should Exercise Change as Your Belly Grows?

Possibly.

As your center of gravity shifts:

• balance may change;
• joints can feel less stable;
• some positions become uncomfortable.

Avoid activities with a high risk of:

• falling;
• collisions;
• abdominal trauma.

Is Sex Safe at 20 Weeks?

For many uncomplicated pregnancies, sexual activity remains safe.

Seek individualized advice if you have:

• unexplained bleeding;
• significant pain;
• leaking fluid;
• cervical problems;
• placenta-related complications;
• clinician instructions to avoid intercourse.

Can You Travel at 20 Weeks?

Many uncomplicated pregnancies can travel during the second trimester.

Before significant travel, consider:

• access to healthcare;
• travel insurance;
• infection risks;
• food and water safety;
• length of travel;
• your personal pregnancy history.

High-risk pregnancies require individualized advice.

Should You Start Preparing for Birth Already?

You do not need a finished birth plan at week 20, but this is a reasonable time to start learning about:

• birth settings;
• antenatal classes;
• pain-relief options;
• breastfeeding;
• newborn care;
• parental leave.

Planning early allows time to ask questions without assuming every decision must be final.

What About Vaccination During Pregnancy?

Vaccination timing varies by country and season.

For example, the NHS recommends pertussis vaccination during pregnancy and notes that it can be offered during the 16–32 week period, commonly around week 20.

Follow the vaccination recommendations for your own country and healthcare system.

When Should You Seek Medical Help at 20 Weeks?

Contact your maternity healthcare service if symptoms concern you.

Seek urgent assessment for:

• heavy vaginal bleeding;
• severe or persistent abdominal pain;
• significant or continuing fluid leakage;
• fainting;
• severe dizziness;
• difficulty breathing;
• high fever;
• severe one-sided leg swelling or pain;
• severe headache with visual changes;
• other symptoms that feel medically urgent.

Online pregnancy information should not be used to diagnose potentially serious symptoms.

Pregnancy Week 20 FAQs

Is 20 weeks halfway through pregnancy?

Approximately yes. A typical estimated pregnancy length is around 40 gestational weeks, making week 20 the conventional halfway milestone.

How big is the baby at 20 weeks?

The NHS estimates the fetus at around 25.6 cm head-to-heel, approximately the length of a banana.

Why did the baby’s length suddenly increase?

Around week 20, measurements begin being described from head to heel instead of head to bottom.

What is vernix?

Vernix caseosa is the white, greasy protective coating covering fetal skin. It helps protect the skin while the fetus remains surrounded by amniotic fluid.

Can you feel the baby move at 20 weeks?

Many people can. Movement may feel like fluttering, tapping, rolling or kicking. Some healthy pregnancies still have less noticeable movement at this stage.

Should you count kicks at 20 weeks?

Usually not. Formal kick counting is generally more relevant later, once a recognizable movement pattern is established.

Can the baby hear at 20 weeks?

Yes. ACOG notes that hearing is functional by this general stage and states that the fetus can hear sounds by week 18.

Can the baby suck its thumb?

Yes. The NHS notes that thumb-sucking can occur around week 20 and helps develop the sucking reflex needed after birth.

What is checked at the 20-week scan?

The standard ultrasound checks fetal physical development, movement, heart rate, growth, amniotic fluid, placenta location and other major anatomical structures.

Is the 20-week scan mandatory?

Ultrasound decisions are ultimately yours, but ACOG recommends offering all pregnant patients a second-trimester structural ultrasound, ideally between 18 and 22 weeks.

Does a normal anatomy scan guarantee a healthy baby?

No. A normal scan is reassuring but cannot detect every congenital, genetic or developmental condition.

Can the baby’s sex be seen at 20 weeks?

Often yes, when fetal position allows, although this is not the primary medical purpose of the scan.

Can the due date change after a 20-week scan?

Usually not if an accurate earlier ultrasound already established gestational age. Later changes to the estimated due date should be uncommon.

Is week 20 still the second trimester?

Yes. Week 20 is firmly within the second trimester.

What Comes Next?

During Pregnancy Week 21, fetal kicks and turns become stronger. The fetus may bring a hand to the mouth and suck its thumb, eyebrows become increasingly visible, and lung development continues.

ACOG describes weeks 21–24 as a period of stronger movement, visible eyebrows, developing fingerprints and footprints, and continued lung maturation.

Previous: Pregnancy Week 19
Next: Pregnancy Week 21
Tool: Pregnancy Due Date Calculator

Medical References

This article is based on current educational information from established medical and public-health organizations, including:

• American College of Obstetricians and Gynecologists (ACOG) — Changes During Pregnancy
• ACOG — Ultrasound Exams
• ACOG — Current Prenatal Screening Guidance
• ACOG — Management of Suboptimally Dated Pregnancies
• NHS — 20 Weeks Pregnant
• MedlinePlus — Fetal Development
• MedlinePlus — Fetal Health and Development

Editorial & Medical Information

Last content review: October 2026

This page provides general educational pregnancy information only. It does not diagnose pregnancy complications, assess fetal wellbeing, interpret ultrasound or genetic-test results, prescribe medication, or replace personalized prenatal care.

Pregnancy symptoms, fetal movement, ultrasound findings and healthcare needs vary between individuals. Contact a qualified healthcare professional for personal concerns about movement, bleeding, severe pain, fluid leakage, ultrasound findings, medications or other pregnancy symptoms.

Conclusion

Pregnancy week 20 is a major halfway milestone and one of the most important prenatal imaging stages. The NHS estimates the fetus at around 25.6 cm from head to heel and notes that the skin is now protected by vernix caseosa. Fetal activity continues increasing, and thumb-sucking may help develop the sucking reflex needed after birth.

Neurological, auditory and digestive development is also progressing. ACOG notes that during weeks 17–20, hearing becomes functional, the brain region controlling movement is developed, the digestive system is working and lanugo spreads across the body.

Week 20 also falls directly within the 18–22 week anatomy-scan window. ACOG recommends offering this structural ultrasound to all pregnant patients because fetal structural abnormalities can occur regardless of earlier chromosome-screening results.

For the pregnant person, an expanding uterus, stronger fetal movement, back discomfort, heartburn, constipation and leg cramps may become more noticeable. Calf cramps are particularly common around this stage and can occur at night.

Continue evidence-based prenatal care, appropriate nutrition and safe activity. Heavy bleeding, severe pain, significant fluid leakage, fainting, breathing difficulty or other serious symptoms should be medically assessed rather than self-diagnosed online.