Key Milestone Weeks in Pregnancy Second Trimester (Weeks 14–27)
Summary:
At 20 weeks pregnant, you're officially halfway through your pregnancy. This milestone brings a mix of excitement, physical changes, and important health checks. It’s a time when many expectant parents begin to feel more connected to their growing baby and start preparing for what’s ahead. Your baby is developing tastebuds, fingerprints, bones, and even the ability to hear sounds from outside the womb. A key milestone at this stage is the morphology scan, which checks your baby’s growth and organ development and may reveal their sex. Physically, you might notice a growing belly, round ligament pain, and changes in your breathing as your uterus expands.
At 20 weeks pregnant, your uterus has grown to reach your belly button, and your belly typically measures about 20 centimetres, matching the number of weeks you are pregnant. As your uterus expands, it can press against your heart and lungs, occasionally causing breathlessness, especially when lying on your back; lying on your side with a pillow can help. You may also experience round ligament pain, a common but sometimes sharp or cramping sensation caused by the stretching of ligaments that support your uterus. Gentle movement, stretching, and wearing a belly support band can ease discomfort, but it’s always best to speak with your doctor or midwife if you’re concerned.
Tip: Sitting upright, using pillows for support, and practising gentle prenatal yoga can help ease breathlessness as your uterus expands.
At 20 weeks, your baby is about 25cms in length and weighs around 300 grams. Fingerprints have formed, permanent teeth are growing beneath the baby teeth, and if it's a girl, her ovaries already contain eggs. Cartilage is gradually turning into bone, and the bone marrow has begun producing blood cells.
Although the ears are still developing, your baby can now hear sounds from outside the womb. They’re also starting to build up brown fat, also known as adipose tissue, that helps regulate body temperature after birth, ensuring they stay warm in the early days of life. Your baby’s taste buds are working which means your baby may already be experiencing different flavours through the amniotic fluid, which helps prepare them for feeding after birth.
Your baby is also beginning to develop sleep and wake patterns, alternating between active and quieter periods. You may soon start to notice these rhythms.
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FAQs
At 20 weeks pregnant, can I find out the sex of my baby?
Yes, at 20 weeks pregnant, you can often find out the sex of your baby through a routine morphology scan, which is typically performed between 18 and 22 weeks of pregnancy. This detailed ultrasound checks your baby’s development, including organs and body structures, and depending on your baby’s position during the scan, the sonographer may be able to identify the sex if you would like to know.
Can I dye my hair while pregnant?
While there is limited evidence showing harm from hair dye during pregnancy, it's best to be cautious, especially during the first trimester. Using semi-permanent dyes, avoiding harsh chemicals like ammonia, and ensuring good ventilation during application are recommended.
Skin around your scalp may be more sensitive during pregnancy, increasing the risk of allergic reactions. Dermatologists recommend doing a patch test before dyeing and avoiding prolonged exposure to chemicals. Using foils to keep dye off the scalp or switching to natural alternatives like henna may reduce risks.
Is it normal to have heartburn and headaches at 20 weeks pregnant?
Heartburn is a common symptom during pregnancy, affecting up to 80% of women, particularly in the second half. It’s caused by hormonal changes that relax the muscle at the base of the oesophagus, allowing stomach acid to rise, and is often worsened by the growing uterus pressing against the stomach. The condition known as gastro-oesophageal reflux disease (GORD) can lead to burning chest pain and regurgitation.
Fortunately, it can usually be managed with lifestyle adjustments and pregnancy-safe medications such as antacids or proton pump inhibitors, under the guidance of a healthcare professional. Headaches are also a common experience during pregnancy, particularly in the second trimester, and are often linked to hormonal changes, increased blood volume, stress, or dehydration. While usually harmless, persistent or severe headaches should be discussed with a healthcare provider to rule out more serious conditions such as pre-eclampsia.
How many weeks is pregnancy?
Pregnancy is typically calculated as 40 weeks, starting from the first day of your last menstrual period, not the date of conception. This method accounts for the two weeks before ovulation and fertilisation, which is why pregnancy is considered 40 weeks even though the baby spends around 38 weeks in the womb. The pregnancy is divided into three trimesters:
- First trimester: Weeks 1–12
- Second trimester: Weeks 13–27
- Third trimester: Weeks 28–40
Babies are considered full term if born between 37 and 42 weeks.
At 20 weeks pregnant will I get stretch marks?
It is normal to begin developing stretch marks during pregnancy, including around the 20-week mark, although they tend to become more noticeable in the third trimester. Skin changes are common due to hormonal shifts and the physical stretching of the skin as your belly grows. While most over-the-counter skincare products are considered safe to use during pregnancy, including moisturisers and vitamin A-based creams in low concentrations, it's important to avoid products with high absorption rates like hydroquinone. If you're concerned about stretch marks or unsure which products are safe, it's best to consult your healthcare provider.
At 20 weeks pregnant can I fly and travel?
Yes, you can fly at 20 weeks pregnant, but there are important considerations to keep in mind to ensure your safety and comfort. Most airlines allow pregnant women to fly up to 28 weeks, but policies vary, especially for multiple pregnancies. It’s essential to check with your airline and obtain a doctor’s letter confirming your due date and fitness to travel. The second trimester (weeks 13–27) is generally the safest time to travel, provided there are no complications. However, pregnant women should avoid long-distance travel if they have high-risk conditions such as gestational diabetes, high blood pressure, or a history of miscarriage. Always carry your maternity notes or antenatal records when flying.
Risks like deep vein thrombosis (DVT) increase during pregnancy, especially on long flights, so it's recommended to stay hydrated, move regularly, and wear compression stockings. Before flying, consult your doctor to assess your individual health and travel plans. Also, ensure your travel insurance covers pregnancy-related issues, including premature birth or cancellation due to complications.
Related reading:
What to expect when you're 18 weeks pregnant
What to expect when you're 22 - 23 weeks pregnant
What to expect when you're 24 weeks pregnant
What to expect when you're 26 - 27 weeks pregnant
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Pregnancy, Birth and Baby. (n.d.). How big is your baby? (Infographic). Australian Government Department of Health and Aged Care. Retrieved August 14, 2025, from https://www.pregnancybirthbaby.org.au/how-big-is-your-baby-infographic. Retrieved 28th July 2025
