16 weeks pregnant: test results and a growth spurt
The week of your first routine second-trimester check in the UK, and often the first chance to hear the heartbeat.
Updated October 13, 2026 · sources checked October 13, 2026
In short
At 16 weeks your baby is about 11.6cm long from head to bottom, pulling random faces and starting to make fists. In the UK this is usually your 16-week appointment, when you get your booking blood test results. Some people feel first flutters from now, but many first-time parents feel nothing until after 20 weeks. This week, write down your questions for that check.
Where you are at 16 weeks
Sixteen weeks closes month four in Cleveland Clinic's grouping (weeks 13 to 16). You are well into the second trimester. Not sure of your exact day count? The pregnancy week calculator tells you, and the due date calculator shows the date it is all counting towards.
Your baby this week
The NHS gives a length of around 11.6cm from head to bottom and compares it to an avocado. Cleveland Clinic describes the fetus at the end of month four as about 5 inches long and about 4 ounces.
- Faces and fists. Your baby is starting to pull faces, though smiles and frowns are random because there is no muscle control yet. The hands can form fists (NHS).
- Arms and legs moving. The developing nervous system lets your baby move arms and legs (NHS).
- Ears and lips. Cleveland Clinic notes that by 16 weeks your baby has lips and that the ears are developed enough to hear you talk. Even with closed eyes, your baby can turn away from light.
A growth spurt is on the way, and you have probably put on some weight too (NHS).
Your body and common symptoms
Constipation is common: hard-to-pass stools that can leave you bloated, queasy and achy. The NHS suggests:
- foods high in fibre, such as wholemeal bread, fruit and veg, beans and lentils
- regular exercise
- plenty of water
- talking to your midwife or doctor if iron supplements seem to make it worse (never stop a prescribed medicine on your own)
Other symptoms the NHS lists around now: swollen or bleeding gums, bloating, indigestion and heartburn, vaginal infections, lingering morning sickness and food cravings. If you feel unwell and it is getting you down, say so at your appointment.
Carbon monoxide. You cannot see, smell or taste it. The NHS notes that routine carbon monoxide tests are done at midwife appointments, and suggests checking that any home detector works (press the test button) and that cooking and heating appliances are well ventilated.
Is this normal? When to call
Not feeling movements yet is normal at 16 weeks, especially in a first pregnancy. So are constipation and bloating.
Call your midwife, GP or OB-GYN straight away for vaginal bleeding, fluid leaking from your vagina, severe or persistent tummy pain, a temperature of 38C (100.4F) or above, or vomiting that stops you keeping fluids down. In the UK, before 20 weeks your early pregnancy unit or maternity unit can help; call NHS 111 if you cannot reach them and 999 in an emergency. In the US, call your provider, or 911 in an emergency.
Appointments and tests around 16 weeks
UK. The NHS 16-week appointment covers your health and wellbeing, the results of earlier screening, information about the 20-week scan, and blood pressure and urine checks. You will also get results from booking bloods, which usually include tests for HIV, hepatitis B and syphilis. Protein in the urine is checked because it can be an early sign of pre-eclampsia. From 16 weeks you can have the whooping cough vaccine; the NHS usually offers it around the 20-week scan, and it can be given any time from 16 to 32 weeks.
US. Your routine prenatal visit usually includes blood pressure and a urine test. ACOG lists urine tests and blood tests for infections among routine tests. If you are considering the quad screen, ACOG gives the window as 15 to 22 weeks.
Your checklist for week 16
For your partner
Come to the 16-week check if you can: it is often the first time you hear the heartbeat on the handheld monitor. And take a look at the carbon monoxide detector while you are at it.
Previous and next week
Week 15: hearing, discharge and balance · Week 17: first movements and stretch marks
Read the full second trimester guide or see all pregnancy weeks.
Questions parents ask
Can I feel my baby move at 16 weeks?
Possibly. The NHS says you should start to feel movements between 16 and 24 weeks, and if this is your first baby you might not feel them until after 20 weeks. Tell your midwife if you have not felt any movement by 24 weeks.
How many months pregnant is 16 weeks?
Cleveland Clinic groups weeks 13 to 16 as month four, so 16 weeks is the end of the fourth month. It describes the fetus at the end of month four as about 5 inches long and about 4 ounces.
What happens at the 16-week appointment?
In England the midwife asks about your health and wellbeing, discusses earlier screening results, tells you about the 20-week scan, and checks your blood pressure and urine (NHS).
Sources
- NHS — Week-by-week guide to pregnancy, week 16 checked October 13, 2026
- NHS — Your antenatal appointments checked October 13, 2026
- NHS — Your baby's movements checked October 13, 2026
- Cleveland Clinic — Fetal Development, week-by-week stages checked October 13, 2026
- ACOG — Routine Tests During Pregnancy checked October 13, 2026
- NHS — Whooping cough vaccine checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.