Pregnancy Week by Week: Find Your Week

By DueDateLab Editorial

This is the DueDateLab pregnancy week-by-week guide. Detailed pages are currently available for weeks 4 to 17, with weeks 18 to 42 planned for later additions. Weeks 1 to 3 appear as context rows because pregnancy dating starts from the first day of the last menstrual period, before most people have a positive test. The goal is a clear weekly map that connects dates, symptoms, development, and safe next steps without turning a week number into a personal medical conclusion.

How pregnancy weeks are counted

Pregnancy weeks are counted from the first day of the last period.[1] The full counted span is 40 weeks from the start of the last period.[2] That is why the counted week can run ahead of time since fertilisation, and why a week-by-week guide needs a short dating explanation before jumping into development details.

Weeks 1 to 3

Pregnancy weeks are counted from the first day of the last menstrual period, which is why a week-by-week pregnancy chart starts before most people have a positive test. Weeks 1 to 3 are included here as context rows only, not as separate pages. The individual guides begin at week 4, when missed-period timing, early symptoms, implantation-related spotting, and the first practical testing questions tend to overlap.[3]

Detailed week pages, weeks 4 to 17

The table below links the detailed weekly pages currently available. Each row is short by design. Each detailed guide carries the fuller weekly explanation, safety notes, calculator links, and source list.

Week What may be happening Guide
Weeks 1 to 3 Context only: pregnancy is counted from LMP before most people have a positive test. See the explainer above
Week 4 Missed-period timing, implantation-related spotting, early symptoms, and first testing questions may overlap.[3] 4 weeks pregnant
Week 5 Many people realise they are pregnant around this point; early brain, spinal-cord, and heart formation are underway.[4] 5 weeks pregnant
Week 6 Rapid early development continues, and symptoms such as nausea or tiredness may become more noticeable.[5] 6 weeks pregnant
Week 7 Brain, face, and limb structures continue developing, while tiredness, sickness, mood changes, or thirst may show up.[6] 7 weeks pregnant
Week 8 The placenta is getting ready to support nutrient and oxygen exchange, and common early symptoms may continue.[7] 8 weeks pregnant
Week 9 Hormone levels and symptoms can feel prominent, while internal organs, bones, face, hands, and feet keep developing.[8] 9 weeks pregnant
Week 10 Near the end of the first trimester, the baby is around 30 mm and movement can be seen on a scan.[10] 10 weeks pregnant
Week 11 Tests may be offered around now, and the baby is around 41 mm from head to bottom.[11] 11 weeks pregnant
Week 12 The first trimester is nearing its close, and the baby is about 5.4 cm from head to bottom.[12] 12 weeks pregnant
Week 13 A small bump may be visible, and movement may still not be felt until around week 17.[13] 13 weeks pregnant
Week 14 The placenta is active, and the baby is around 8.5 cm from head to bottom.[14] 14 weeks pregnant
Week 15 The baby is around 10.1 cm, and lanugo is starting to grow.[15] 15 weeks pregnant
Week 16 The nervous system continues to develop, and a midwife appointment may happen around now.[16] 16 weeks pregnant
Week 17 Some people might start to feel movement, while many first notice it between 18 and 24 weeks.[17] 17 weeks pregnant
Weeks 18 to 42 More weekly guides will be added later. Coming later

Safety in early pregnancy

Safety in early pregnancy

If you are pregnant and have light bleeding or spotting, contact your maternity unit, an early pregnancy unit if you are under 20 weeks, or NHS 111 if you cannot reach those services.[9] Call emergency services for bleeding with severe tummy pain, shoulder pain, faintness, dizziness, loss of consciousness, or heavy bleeding that soaks a pad soon after putting it on. Each detailed week page in this hub repeats this safety routing alongside week-specific context.

Use our Due Date Calculator

Use the Due Date Calculator if you want to estimate your due date from LMP using the 40-week pregnancy convention.[2] The calculator gives a dated result first, then you can use this hub to open the matching weekly guide. If your question is how a week number converts into months, use the Pregnancy Weeks to Months Calculator and Chart.

Use this hub to choose a week, then open the matching guide for development, common symptoms, safety guidance, and calculator context. If you only know a due date, start with the calculator. If you know your LMP date or current week count, start with the matching row above.

Weeks 4 through 17 are available now, and more weekly guides will be added as the series expands.

Related

Sources

  1. Pregnancy due date calculator: NHS. LMP dating and pregnancy-length guidance.
  2. Fetal development: The first trimester: Mayo Clinic. Forty-week pregnancy convention and early development.
  3. Week 4: NHS Best Start in Life. LMP convention and early week-4 symptoms.
  4. Week 5: NHS Best Start in Life. Pregnancy awareness and early development.
  5. Week 6: NHS Best Start in Life. Week-6 development and symptoms.
  6. Week 7: NHS Best Start in Life. Week-7 development and symptoms.
  7. Week 8: NHS Best Start in Life. Placenta and week-8 development.
  8. Week 9: NHS Best Start in Life. Week-9 symptoms and development.
  9. Vaginal bleeding in pregnancy: NHS. Early-pregnancy safety routing.
  10. Week 10: NHS Best Start in Life. Week-10 development and scan-visible movement.
  11. Week 11: NHS Best Start in Life. Week-11 development and tests around this stage.
  12. Week 12: NHS Best Start in Life. Week-12 development and dating-scan window.
  13. Week 13: NHS Best Start in Life. Week-13 bump visibility and movement-window context.
  14. Week 14: NHS Best Start in Life. Week-14 placenta activity and second-trimester start.
  15. Week 15: NHS Best Start in Life. Week-15 lanugo and body-change context.
  16. Week 16: NHS Best Start in Life. Week-16 nervous-system development and midwife appointment.
  17. Week 17: NHS Best Start in Life. Week-17 movement-window guidance.