Free family guide · Pregnancy week by week · First trimester

8 weeks pregnant

Week 8 is in the first trimester in both the US Office on Women's Health (OWH) system and the UK's NHS week-by-week guide.[1][2]

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Sources on this page: OWH; NHS; ACOG; NICHD; WHO; MedlinePlus; NIMH; HRSA; CDC

This page shares what health organizations say. It is not medical advice. It is general information. Talk to your doctor, midwife or pediatrician about your own situation.

In an emergency, call 911.

At a glance

  • The NHS says the baby is around 16 mm long.[3]
  • The NHS says the baby will double in size by next week, and the arms are longer than the legs.[3]
  • If you are peeing often, the NHS suggests drinking more during the day and less in the evening.[3]

Which trimester is week 8?

OWH counts the trimesters as weeks 1 to 12, 13 to 28 and 29 to 40.[1] The NHS guide counts them as weeks 4 to 12, 13 to 27 and 28 to 41.[2] ACOG counts the first trimester to 13 weeks 6 days, the second from 14 weeks to 27 weeks 6 days, and the third from 28 weeks to 40 weeks 6 days.[4]

All three place week 8 in the first trimester.[1][2][4]

ACOG says pregnancy is counted from the first day of the last menstrual period, so 2 weeks are counted at the beginning when you are not yet pregnant.[4]

Your body this week

The NHS lists these symptoms around week 8:[3]

  • tiredness;[3]
  • feeling sick;[3]
  • peeing more often;[3]
  • mood swings;[3]
  • bloating.[3]

Your baby this week

The NHS says the baby is around 16 mm long.[3]

The NHS says the baby will double in size by next week, and the arms are longer than the legs.[3] It says the embryo is now called a fetus, and the placenta is sprouting branches to attach to the wall of the womb.[3]

OWH says the heart beats steadily by about week 8.[1]

Visits and tests around week 8

Sources differ

Sources give different timing for the first prenatal visit:[5][6][7][8]

  • NICHD says the first visit usually happens after about week 8, and it is one of the longest visits.[5]
  • The NHS says the booking appointment is usually between weeks 8 and 12 and takes around an hour.[6]
  • ACOG says before 10 weeks after your last period is the ideal time to start prenatal care.[7]
  • The World Health Organization (WHO) recommends a first contact within the first 12 weeks.[8]

OWH lists chorionic villus sampling (CVS) at weeks 10 to 13.[9] ACOG also says CVS is done between 10 and 13 weeks.[10]

Sources differ

Sources give different weeks for first-trimester screening:[9][11]

  • OWH lists the first trimester screen at weeks 11 to 14.[9]
  • ACOG says the blood test and nuchal translucency ultrasound are usually done together between 10 and 13 weeks.[11]

ACOG says cell-free DNA screening can be done from 10 weeks, with results in about 1 week.[11]

The NHS says its dating scan is done at 8 to 14 weeks.[6]

MedlinePlus says prenatal testing is optional and is your decision, made with your provider.[12]

For a healthy pregnancy, NICHD describes visits once a month until 28 weeks.[5]

Things to do this week

  • If you are peeing often, the NHS suggests drinking more during the day and less in the evening.[3]
  • For your emotions, the NHS suggests rest, small meals, mindfulness and talking to your midwife.[3]
  • The NHS advises 400 micrograms of folic acid a day until at least week 12.[6]
  • MedlinePlus says to keep caffeine under 200 mg a day, about 1 to 2 small cups of coffee or tea.[13]

Feelings check-in

The National Institute of Mental Health (NIMH) says perinatal depression includes depression during pregnancy, and its signs last at least 2 weeks.[14]

HRSA says the National Maternal Mental Health Hotline, 1-833-852-6262, takes calls and texts 24/7 in English and Spanish.[15]

When to call your provider or get help

CDC lists urgent warning signs to watch for during pregnancy and in the year after birth, including:[16]

  • a headache that will not go away or gets worse;[16]
  • dizziness or fainting;[16]
  • a fever of 100.4°F (38°C) or higher;[16]
  • severe nausea and vomiting;[16]
  • severe belly pain that does not go away;[16]
  • vaginal bleeding or leaking fluid;[16]
  • thoughts of harming yourself or the baby.[16]

MedlinePlus says some people spot in early pregnancy and do not miscarry, but any bleeding should prompt a call to a provider.[17]

Questions families ask

Which trimester is week 8?

OWH places week 8 in the first trimester.[1] The NHS guide places it in the first trimester.[2] ACOG places it in the first trimester.[4]

How big is the baby at 8 weeks?

The NHS says the baby is around 16 mm long.[3]

When is the first prenatal visit?

NICHD says it usually happens after about week 8.[5] ACOG says before 10 weeks after your last period is ideal.[7] WHO recommends a first contact within the first 12 weeks.[8]

Free from UpOnly Learning. Written for families of every faith. No outside ads and no affiliate links. Every fact on this page comes from the sources listed below. How we source and review these pages

Updated 2026-10-24: first published.

Sources

All sources were opened and checked on the date shown.

  1. Office on Women's Health (HHS). Stages of pregnancy. Checked October 24, 2026.
  2. NHS (United Kingdom). Week-by-week guide to pregnancy. Checked October 24, 2026.
  3. NHS (United Kingdom). 8 weeks pregnant guide. Checked October 24, 2026.
  4. American College of Obstetricians and Gynecologists. How Your Fetus Grows During Pregnancy. Checked October 24, 2026.
  5. Eunice Kennedy Shriver National Institute of Child Health and Human Development (NIH). What happens during prenatal visits?. Checked October 24, 2026.
  6. NHS (United Kingdom). 4 weeks pregnant guide. Checked October 24, 2026.
  7. American College of Obstetricians and Gynecologists. Prenatal Care. Checked October 24, 2026.
  8. World Health Organization. New guidelines on antenatal care for a positive pregnancy experience (news release, Nov 7, 2016). Checked October 24, 2026.
  9. Office on Women's Health (HHS). Prenatal care and tests. Checked October 24, 2026.
  10. American College of Obstetricians and Gynecologists. Prenatal Genetic Diagnostic Tests. Checked October 24, 2026.
  11. American College of Obstetricians and Gynecologists. Prenatal Genetic Screening Tests. Checked October 24, 2026.
  12. MedlinePlus (National Library of Medicine). Prenatal Testing. Checked October 24, 2026.
  13. MedlinePlus (National Library of Medicine). Caffeine in the diet. Checked October 24, 2026.
  14. National Institute of Mental Health (NIH). Perinatal Depression. Checked October 24, 2026.
  15. Health Resources and Services Administration (HRSA). National Maternal Mental Health Hotline. Checked October 24, 2026.
  16. Centers for Disease Control and Prevention (HEAR HER campaign). Urgent Maternal Warning Signs and Symptoms. Checked October 24, 2026.
  17. MedlinePlus (National Library of Medicine). Miscarriage. Checked October 24, 2026.