Second trimester
16 weeks pregnant
Your baby is about the size of an avocado
By Emma Whitfield · Pregnancy & Baby Writer
How big is the baby at 16 weeks pregnant?
At 16 weeks pregnant, your baby is about the size of an avocado, roughly 11.6cm and around 100g. The baby's muscles are getting stronger, the eyes can move, and the heart pumps around 25 litres of blood a day. They're developing patterns of activity and rest. These are typical averages — your midwife's measurements are the ones that matter for your pregnancy.
What might you feel at 16 weeks?
Most people at 16 weeks notice some mix of the symptoms below — and plenty notice none of them. Some people feel the first flutters ("quickening") around now, especially in a second pregnancy — a bubbly or fluttery sensation low down. First-timers often feel it a few weeks later. None of this is a diagnosis; contact your midwife if something worries you.
Common symptoms this week
- Possible first flutters (quickening), especially second pregnancies
- Steadier energy
- Growing bump
Symptom lists are typical, never exhaustive — and having none of them is normal too.
What should you do at 16 weeks pregnant?
The useful job this week is practical, not medical. Start sleeping on your side rather than your back as your bump grows — the left side is often most comfortable and best for blood flow. Pair it with the NHS week-by-week guide if you want a second description of the same stage.
Week 16 checklist
- Attend your 16-week midwife appointment — blood pressure, urine check and your booking blood results
- Have the whooping cough (pertussis) vaccine, offered from 16 weeks — it protects your newborn
- Start sleeping on your side as the bump grows
What else is useful at 16 weeks?
Use the week page for size and symptoms; use the guides below for the decisions that actually sit in this window — pay, packing, car seats, labour signs.
16 weeks pregnant: common questions
When will I feel the baby move for the first time?
Usually between 16 and 24 weeks — earlier in second pregnancies, later for first-timers, where 18–22 weeks is typical. Early movement feels like flutters, bubbles or popping rather than kicks, and an anterior placenta can muffle it for a few more weeks.
How big is my baby at 16 weeks pregnant?
At 16 weeks, your baby is approximately the size of an avocado, about 11.6cm and around 100g. These are approximate averages — every baby grows at its own pace.
What's happening at 16 weeks pregnant?
The baby's muscles are getting stronger, the eyes can move, and the heart pumps around 25 litres of blood a day. They're developing patterns of activity and rest. For you: some people feel the first flutters ("quickening") around now, especially in a second pregnancy — a bubbly or fluttery sensation low down. first-timers often feel it a few weeks later.
Which trimester is 16 weeks?
16 weeks pregnant is in the second trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night. Reviewed August 2026.