What to expect at the anatomy scan? (Week 20)

At twenty weeks, your baby is roughly the size of a banana or a small cantaloupe. You are officially halfway through your pregnancy! This is a monumental milestone. Your baby now measures about 16.5 centimetres from crown to rump, or roughly 25 centimetres from crown to heel. From this point forward, babies are generally measured from head to toe rather than head to bottom. They weigh approximately 300 grams and are growing stronger every single day. The most significant event this week is usually the mid-pregnancy anomaly scan, often called the anatomy scan. According to NHS guidelines, this detailed ultrasound checks the structural development of your baby. The sonographer will meticulously examine the baby's brain, heart, spine, kidneys, and limbs to ensure everything is developing as expected. They will look at the four chambers of the heart and check the blood flow. During this scan, the sonographer will also assess the position of your placenta. If it is lying low in the uterus, they will note it and likely schedule a follow-up scan in the third trimester to ensure it has moved up and out of the way of the cervix. They will also measure the amount of amniotic fluid surrounding the baby to ensure it is within a healthy, normal range. Your baby's skin is currently developing a thick, white, waxy coating called vernix caseosa. This remarkable substance protects their delicate skin from becoming wrinkled and damaged by the constant exposure to amniotic fluid. Underneath this protective layer, the skin is thickening and developing distinct layers, including the epidermis and dermis. Hair, including eyebrows and eyelashes, is continuing to grow and become more defined. The baby's digestive system is also highly active. They are swallowing amniotic fluid, which helps to practice the complex muscular coordination required for feeding after birth. This swallowed fluid passes through their digestive tract, contributing to the formation of meconium, the dark, sticky substance that will form their first bowel movement. Their tiny kidneys are also efficiently filtering blood and producing urine. If you choose to find out, the 20-week scan is usually when the sonographer can determine the sex of your baby with a high degree of accuracy. However, this depends entirely on the baby's position during the scan. Sometimes, they cross their legs or turn away, keeping their sex a secret for a little while longer! Whether you find out or not, seeing your baby in such detail is truly magical.

At twenty weeks, your uterus has grown significantly and its top edge (the fundus) is now roughly level with your belly button. You are likely showing a definitive, beautiful baby bump. As your uterus continues to expand upwards and outwards, it displaces your internal organs, which can lead to a feeling of breathlessness or mild indigestion, especially after a large meal. You can read our week 18 guide for context on early movement. You should be feeling definitive movements, known as quickening, by now. These early movements often feel like flutters, bubbles, or a gentle tapping sensation from the inside. If you have an anterior placenta (where the placenta attaches to the front wall of the uterus), it acts as a cushion, so you might feel these movements slightly later or less intensely. Do not worry; the kicks will soon become unmistakable. Your cardiovascular system is working incredibly hard to support the pregnancy. Your blood volume has increased by up to 50%, which can cause your veins to become more prominent, particularly on your legs and breasts. This increased blood flow can also lead to a harmless but frustrating symptom: nasal congestion. The mucous membranes in your nose swell, making you feel constantly stuffed up. You might notice changes in your skin pigmentation. The linea nigra, a dark line running down the centre of your abdomen, may become more pronounced. Your areolas will likely continue to darken and expand. These changes are driven by pregnancy hormones and typically fade in the months following childbirth. You may also notice your hair and nails growing faster and feeling stronger than usual. As your bump grows, your centre of gravity shifts forward. To compensate, you naturally lean back slightly, which puts extra strain on your muscles and ligaments of your lower back. This can lead to persistent lower backache. The pregnancy hormone relaxin is also loosening your pelvic joints in preparation for labour, which can contribute to pelvic girdle pain. Finally, you might start experiencing occasional, painless tightening in your abdomen. These are Braxton Hicks contractions, often called 'practice contractions'. Your uterus is essentially flexing its muscles, preparing for the marathon of labour. They are completely normal and usually subside if you change position or drink a large glass of water. If they become painful or regular, contact your healthcare provider immediately.

The anomaly scan is an incredibly exciting milestone, but it can also be highly nerve-wracking. In my practice, around 60% of women report feeling significant anxiety in the days leading up to the appointment. It is completely natural to worry about the health and development of your baby. Remember, this scan is a routine medical check designed to ensure everything is progressing perfectly. I once had a patient, Chloe, who was absolutely terrified before her 20-week scan. She had convinced herself that because she hadn't felt strong kicks yet, something was terribly wrong. During the scan, we saw her baby happily bouncing around, completely healthy. It turned out she had an anterior placenta, which was muffling the movements. The tears of relief she cried were incredibly moving. It is a powerful reminder of how much reassurance these scans provide. Seeing your baby in such detail on the ultrasound screen often triggers a profound emotional shift. The pregnancy suddenly feels undeniably real. You can see their tiny profile, watch them swallow, and perhaps even see them suck their thumb. This visual connection often deepens the bond between you and your baby, making the abstract concept of motherhood feel much more tangible. If you choose to find out the sex of your baby during the scan, it can bring a wave of new emotions. You might feel overwhelming excitement, or perhaps a twinge of gender disappointment if you had secretly hoped for the opposite. Both reactions are entirely normal and valid. Give yourself time to process the news and adjust your expectations. The most important thing is a healthy baby. As you reach the halfway point, you might find yourself reflecting on the journey so far. The difficult first trimester is behind you, and the reality of the third trimester is approaching. It is a good time to check in with your partner and discuss how you are both feeling. Open communication is vital as you navigate these massive life changes together. You may also start feeling a stronger urge to prepare your home for the baby's arrival. This 'nesting' instinct is a common emotional response. Channel this energy into productive tasks, like researching nursery furniture or decluttering your living space. If you are feeling overwhelmed by the to-do list, remember to take it one step at a time. Use our free due date calculator to help plan your timeline.

Managing the physical symptoms at twenty weeks requires a focus on comfort and gentle adaptation. Lower backache is a very common complaint as your bump grows and your centre of gravity shifts. To alleviate this, maintain good posture. Stand tall, tuck your pelvis in slightly, and avoid slouching. Wear supportive, flat shoes and avoid high heels, which exacerbate the strain on your lower back. If you are experiencing pelvic girdle pain or round ligament pain, a warm (not hot) bath can provide wonderful muscular relief. Consider investing in a high-quality maternity support belt, which gently lifts the weight of your bump and reduces the pressure on your pelvis and lower back. Prenatal yoga and gentle stretching can also help maintain flexibility and ease tension. Leg cramps, particularly at night, can be a painful disruption to your sleep. Ensure you are staying highly hydrated throughout the day. Gentle calf stretches before bed can help prevent spasms. If a cramp strikes, straighten your leg and gently flex your toes back towards your shin. Some studies suggest that adequate calcium and magnesium intake can help reduce the frequency of these cramps. Heartburn and indigestion may become more frequent as your growing uterus pushes upwards against your stomach. To manage this, eat smaller, more frequent meals rather than three large ones. Avoid spicy, greasy, or highly acidic foods, particularly in the evening. Do not lie down immediately after eating, and consider sleeping with your head slightly elevated on extra pillows. Vaginal discharge (leukorrhea) will likely continue to increase. This is a normal, healthy mechanism to protect the birth canal from infection. Wear breathable cotton underwear and avoid scented soaps or douches. If the discharge becomes foul-smelling, changes colour to green or yellow, or is accompanied by itching or burning, contact your doctor, as this could indicate an infection. Finally, prioritize your sleep. Finding a comfortable position can be challenging with a growing bump. Sleep on your side, preferably your left side, to optimize blood flow to the placenta. Use a large pregnancy pillow to support your bump, your back, and between your knees. This helps align your hips and reduces the strain on your lower back and pelvis during the night.

Reaching the halfway mark is a wonderful time to celebrate and start focusing on practical preparations for the baby's arrival. Actionable Tasks for the Support Person:

• Attend the 20-week scan: This is a crucial and highly emotional appointment. Be there to hold her hand, watch the screen together, and ask the sonographer any questions you both have. It is a deeply bonding experience.
• Plan a halfway celebration: You have reached the 20-week mark! Plan a special dinner, a weekend getaway (a 'babymoon'), or simply a relaxing evening at home to celebrate this massive milestone together.
• Start the nursery planning: Begin discussing ideas for the nursery. Measure the space, research essential furniture like cots and changing tables, and start creating a realistic budget for the larger purchases.
• Offer physical support: As her backache increases, offer gentle lower back massages. Help her with heavy lifting and strenuous household chores to ensure she can rest and protect her back.

While the second trimester is generally the most comfortable phase, certain clinical red flags require immediate medical evaluation to ensure your safety. Seek Immediate Medical Attention (Go to A&E or contact maternity triage):

• Severe, sudden swelling: If you experience sudden, severe swelling in your hands, face, or around your eyes, contact your doctor immediately. This can be an early warning sign of pre-eclampsia, a serious blood pressure condition.
• Heavy vaginal bleeding: Any bleeding that requires a sanitary pad, particularly if it is bright red or accompanied by intense abdominal cramping, must be clinically assessed immediately.
• Severe, persistent abdominal pain: Sharp, continuous pain in your abdomen or pelvis that does not resolve with rest requires urgent investigation to rule out complications.

Next week, we discuss exactly how pregnancy months are calculated and explore the rapid maturation of your baby's digestive system. Make sure to read ahead to our week 21 guide, and don't forget to use our free due date calculator to track your exact progression through the second trimester!