Baby is the size of a avocado
👶 Baby's development
Gender may be visible on ultrasound. Active movement — though most moms feel it 2–4 weeks later.
💛 How mom feels
Some moms feel the first movements — like butterflies. Second trimester screening.
📖 Tip of the week
Some moms feel the first movements — a light fluttering in the belly. Eyes respond to light, though lids are still closed. This is a good time for the second trimester blood screening.
🔬 Detailed baby development
- The musculoskeletal system is maturing — the fetus can make coordinated limb movements
- Eyebrows and eyelashes are beginning to grow
- The circulatory system is fully functional with the heart pumping about 25 quarts of blood per day
- The fetus may begin sucking its thumb, a reflex important for future feeding
- Toenails are starting to grow on the tiny toes
- The fetus is about 11.6 cm long and weighs approximately 100 grams, roughly the size of an avocado
🤱 What mom may feel
- Some first-time mothers may feel the first faint flutters of fetal movement (quickening)
- Backaches may begin as posture changes to accommodate the growing uterus
- Constipation may worsen — iron supplements can contribute to this
- Skin may develop dark patches (chloasma/melasma) on the face
- Increased vaginal discharge (leukorrhea) is normal if clear or white and odorless
🏥 Tests and check-ups
If not yet performed, the quad screen blood test is optimally drawn between weeks 16-18. Second-trimester AFP (alpha-fetoprotein) screening specifically evaluates risk for neural tube defects like spina bifida. Regular prenatal visit includes weight, blood pressure, urine protein, and glucose check.
💡 Tips for this week
- Wear supportive, low-heeled shoes to help with balance and reduce back pain
- Practice good posture: stand tall, avoid locking your knees, and sit with back support
- Eat probiotic-rich foods (yogurt, kefir) to help with digestion and constipation
- Begin thinking about prenatal classes and hospital tours — register early
- If taking iron supplements, take them with vitamin C for better absorption and avoid taking with dairy
❓ Frequently asked questions
What does quickening feel like?
Quickening is often described as fluttering, bubbling, or a light tapping sensation in the lower abdomen. Some women mistake it for gas at first. The movements become more distinct and frequent as the baby grows.
Should I be worried about back pain?
Mild to moderate back pain is very common as your center of gravity shifts. Strengthening exercises, proper posture, prenatal massage, and warm compresses can help. Severe or persistent back pain should be discussed with your provider.
Is vaginal discharge normal?
Increased thin, white, mild-smelling discharge (leukorrhea) is normal during pregnancy due to increased estrogen. However, if the discharge is green, yellow, foul-smelling, or accompanied by itching, contact your provider as it may indicate an infection.
Can I find out the baby's gender at 16 weeks?
Some ultrasound providers may be able to determine the sex at 16 weeks, but accuracy improves significantly at the anatomy scan around 18-22 weeks. NIPT blood test results (if performed earlier) would already include sex information.
📝 Week 16 of pregnancy: what's happening
At week 16, your baby measures around 11.6 cm and weighs approximately 100 g — comparable in size to an avocado. The musculoskeletal system is becoming more coordinated, and your baby is now making active movements, though you may not yet feel them. The eyes are slowly moving from the sides of the head to a more forward-facing position. Your baby’s circulatory system is now fully functional, with the heart pumping around 25 litres of blood per day, and fingernails are beginning to form.
Many women begin to feel the first flutters of fetal movement around this time, often described as a gentle ‘bubbling’ or ‘popping’ sensation known as quickening. If this is your first pregnancy, you may not notice these movements until week 18–20; second-time mothers often recognise them earlier. Your bump is becoming more noticeable, and you may need to start considering maternity clothing for comfort. Some women experience back pain as the centre of gravity shifts — supportive footwear and good posture are helpful.
A routine 16-week antenatal appointment is standard in NHS care, where your midwife will check your blood pressure, test your urine, discuss the results of any screening tests, and measure your uterus. This is a great opportunity to ask any questions and discuss how you are feeling emotionally as well as physically. If you experience any sudden swelling, severe headaches, or visual disturbances, contact your midwife or maternity unit promptly as these can be signs of pre-eclampsia, though this is rare at this stage.
Consider enrolling in antenatal classes — NHS classes (such as those run by the National Childbirth Trust or local NHS trusts) can fill up quickly, especially in busy areas, so it’s worth booking early. These classes cover labour, birth, infant feeding, and newborn care, and are an excellent way to meet other expectant parents. Think about when you plan to tell your employer about your pregnancy — you are legally required to notify them in writing at least 15 weeks before your due date to access statutory maternity rights in the UK. Begin researching your maternity leave entitlements.
⚠️ When to see a doctor
- Vaginal bleeding of any amount
- Severe headache or vision changes
- Severe abdominal or lower back pain
- Swelling of face and hands (possible preeclampsia)
- Decreased or absent fetal movement after 20 weeks
- Blood pressure above 140/90
Sources
- WHO recommendations on antenatal care (2016)
- ACOG Practice Bulletins
- Williams Obstetrics, 26th Edition
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