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Second trimester

16 weeks pregnant

At 16 weeks your baby's developing nervous system lets them move their arms and legs and make fists, and hearing keeps developing. Many people can't feel movement yet, although some who have been pregnant before notice early flutters around now. In the UK, a routine midwife appointment is offered at about this time.

This page covers 16 weeks 0 days to 16 weeks 6 days (16+0 to 16+6), counted from the first day of the last period. Check how far along you are

Enter it to see the calendar dates of your week 16.

Botanical illustration of an avocado

About the size of an avocado

Typical estimated weight 145 g (5 oz) at 16+0, about 175 g (6 oz) by 16+6. This is the 50th centile; healthy babies commonly vary by about 12.7% either way.1

A reference value, not a measurement of your baby.

How your baby is developing

  • The developing nervous system allows your baby to move their arms and legs and to make fists.2
  • Your baby can stretch, yawn and make faces. These facial expressions are random for now, because there is no muscle control yet.2,3
  • The ears are developed enough to pick up sounds such as your voice. The eyes are still closed, but your baby may turn away from bright light.3
  • The skin is still very thin, almost see-through, and fine lanugo hair grows on the head.4
  • Bones continue to harden, and the liver and pancreas are beginning to produce their secretions.4

Changes you may notice

Everyone’s experience is different. You may notice some of these, or none.

  • You have likely gained some weight by now, and your bump may be more noticeable, especially if you have been pregnant before.2,3
  • Some people who have been pregnant before notice early movements, often a fluttering or bubbling feeling, from about 16 weeks. In a first pregnancy it's common not to feel movement until about 20 weeks or later.5,6
  • Constipation is common. High-fiber foods, staying active and drinking plenty of water can help. If you take iron supplements or other medicines, check with your midwife or doctor before stopping anything.2
  • Other possible symptoms include swollen or bleeding gums, round ligament pain, headaches, nosebleeds, heartburn, leg cramps, feeling hot and swollen hands and feet. Get medical advice for any vaginal bleeding.2

Care around this week

  • In the US, the anatomy ultrasound is usually done between 18 and 22 weeks. UK: a midwife appointment is offered at around 16 weeks. You may hear the heartbeat, your blood pressure and urine are checked (protein in the urine can be a sign of pre-eclampsia), and you get the results of your booking blood tests.2,7,8
  • UK: the whooping cough (pertussis) vaccine can be given from 16 weeks. It is usually offered around 20 weeks, ideally before 32 weeks. In the US, the Tdap vaccine is recommended later, during weeks 27 through 36 of each pregnancy.9,10
  • UK midwives now routinely test for carbon monoxide, which you cannot see, smell or taste. It's worth checking that any carbon monoxide alarm at home is working.2

Questions to ask your provider

  • Can we go over my booking blood test results?
  • When is the best time for me to have the whooping cough (Tdap) vaccine?
  • Are my blood pressure and urine results what you'd expect at this stage?
  • When will my anatomy scan be, and can someone come with me?
When to contact your provider straight away

Call 911 (US) or 999 (UK) in an emergency, such as heavy bleeding or bleeding with severe pain, a seizure, chest pain, or severe trouble breathing.11,12,13,14

These symptoms are not always serious, but each one needs prompt advice from your provider, midwife or maternity unit (or NHS 111 in the UK if you cannot reach them) rather than waiting for your next appointment, and it helps to tell them you are pregnant.

  • Vaginal bleeding or spotting at any stage of pregnancy. Call 911 or 999 if the bleeding is heavy or comes with severe belly pain, shoulder pain, or feeling faint or dizzy.13,15
  • Fluid leaking or gushing from your vagina, or discharge that is unusual for you. Get checked straight away if the fluid is greenish, colored or smells bad.13,14,16,17
  • Your baby moving less than usual, not moving, or a change in their usual pattern of movements. Call immediately, even in the middle of the night, and do not use a home Doppler to check yourself.6,13
  • A severe headache that does not go away with simple painkillers or gets worse, or sudden changes in your vision such as blurring or seeing flashing lights.11,13,14
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.11,13,14
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.11,13,18
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.17,18
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.13,14,17
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.13,14
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.19
  • Being sick so often that you cannot keep food or drink down, or signs of dehydration such as dark urine, peeing very little, or feeling dizzy.13,20
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.13,21

Questions about 16 weeks

Can you feel the baby move at 16 weeks?

Some people can, especially if they have been pregnant before. Early movements often feel like fluttering or bubbles. Many people don't feel anything yet: movements are usually first felt between 16 and 24 weeks, and in a first pregnancy often not until after 20 weeks.5,6

When can I get the whooping cough vaccine in pregnancy?

In the UK it can be given from 16 weeks and is usually offered around 20 weeks. In the US, Tdap is recommended during weeks 27 through 36 of each pregnancy, preferably early in that window.9,10

Will I hear my baby's heartbeat at 16 weeks?

Your midwife may listen for the heartbeat at an appointment around this time. The NHS advises against using a home doppler, because hearing a heartbeat does not mean your baby is well.2,6

Sources

  1. In utero analysis of fetal growth: a sonographic weight standardRadiology 181(1):129–133, 1991
  2. 16 weeks pregnant guideNHS Best Start in Life
  3. Fetal development: week-by-week stages of pregnancyCleveland Clinic
  4. Fetal developmentUS National Library of Medicine
  5. Quickening in pregnancyCleveland Clinic
  6. Your baby's movementsNHS (England)
  7. Ultrasound ExamsAmerican College of Obstetricians and Gynecologists
  8. Your antenatal appointmentsNHS (England)
  9. Vaccinations in pregnancyNHS (England)
  10. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  11. Pre-eclampsiaNHS (England)
  12. Epilepsy and pregnancyNHS (England)
  13. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  14. Pregnancy symptoms you need to get help forNHS (England)
  15. Vaginal bleeding in pregnancyNHS (England)
  16. Signs of going into labourNHS Best Start in Life
  17. Premature labour and birthNHS (England)
  18. Stomach pain in pregnancyNHS (England)
  19. Itching in pregnancyNHS (England)
  20. Severe vomiting in pregnancyNHS (England)
  21. Depression in pregnancyNHS (England)

Links checked November 12, 2026. Citing a source does not mean it endorses this site.

Written from the sources above and checked against them on 2026-11-12. Not reviewed by a clinician. Our editorial policy