8 weeks pregnant: what is happening this week

Eight weeks is a growth week. Your baby is around 16 mm now, and behind the scenes the placenta is getting ready for its big job — bringing in nutrients and oxygen, carrying out waste.^[1] Tiredness, sickness, and peeing more often are the classic companions.^[1] Development terminology starts to shift around this stage too, so this page keeps its wording neutral. Here is what the week looks like, what it may feel like, and when to use the safety route instead of a symptom list.

Watch: your baby at week 8

30 sec

A calm, 30-second recap of week 8, from our channel @duedatelab.

What is happening at 8 weeks pregnant

The dating rule has not changed: the count runs from the first day of your last menstrual period across a 40-week span, with conception usually about two weeks in.^[2] That two-week offset still matters at week 8 when you compare your week number with symptoms or development. The label is a dating convention — a very useful one — not a count from fertilisation.

What makes week 8 feel different is the sense of infrastructure being built. The placenta is getting ready to provide nutrients and oxygen and remove waste^[1] — the supply line for everything that follows. That makes this week a bridge between the early post-test blur and the booking appointments and scan windows coming next. For many people it is also simply a heavy-symptom week, though the pattern varies.

On sizes: the exact measurement on this page comes from one source, with broader development context from the others.^[1][2][3] If a scan or a care note has given you a different number, trust the local record — it is about you. This page is about week 8 in general.

Your baby's development this week

Sixteen millimetres, give or take^[1] — and growing in every direction. The arms, legs, and head are all growing, and the placenta is preparing to take over nutrient and oxygen exchange.^[1] Your baby is building both itself and its own life-support system in the same week.

You may also notice different sources switching words around now — this is the stage where “embryo” starts giving way to “foetus”, and different references draw that boundary in different places.^[1][2][3] The vocabulary line is genuinely fuzzy; the development underneath it is not. This page keeps the wording neutral and the facts anchored to the source that supplies them.

For the wider first-trimester picture there is good supporting context beyond this page,^[2][3] but the size number deliberately stays with a single source — one number, one anchor, less confusion for everyone.

What may be happening to you

Tiredness, sickness, and peeing more often — the week-8 trio.^[1] The tiredness runs deep in the first 12 weeks especially, tangled up with the hormonal changes that can also leave you feeling nauseous or emotional.^[4] Tender breasts, fatigue, more urination, and nausea complete the familiar list.^[5] If you are living several of these at once, this week can feel like work. Be kind to yourself.

Nausea may be constant, absent, or different every day — all three are normal. It is very common in early pregnancy and usually clears by weeks 16 to 20,^[6] with typical onset between the 4th and 7th week.^[7] By week 8, some people are already in the thick of it, while others are still waiting to see what the fuss is about.

It is natural to hunt for patterns in all this — more symptoms today, fewer yesterday, what does it mean? Usually nothing a checklist can tell you. A page can say which symptoms sources commonly list; it cannot read your pregnancy from their presence or absence. If there is bleeding, pain, faintness, dizziness, or vomiting that stops you keeping fluids down, stop comparing and use the safety section below.

Safety: when to get help in early pregnancy

NHS pregnancy-bleeding guidance is the main safety source for this section.^[8] NHS nausea and vomiting guidance also says to use care routes if vomiting prevents food or fluids from staying down or if there are dehydration signs.^[6] NHS ectopic guidance is included because symptoms usually develop between the 4th and 12th weeks, but this page does not try to identify a cause from symptoms.^[9]

Booking your antenatal care

By week 8, a pregnancy test has often already happened, but the NHS testing rules still matter for readers arriving with uncertain dates: most pregnancy tests can be used from the first day of a missed period, and if the next period date is unknown, to test at least 21 days after unprotected sex.^[10] NHS also says hCG starts to be produced around 6 days after fertilisation.^[10]

Week 8 is the start of a more practical care window. NHS describes the booking appointment as usually happening between 8 and 12 weeks and says the first midwife appointment should happen before 10 weeks where possible.^[11] NHS also says screening for sickle cell and thalassaemia should be offered before 10 weeks.^[11]

The dating scan is usually later. NHS says the 12-week scan is offered around 10 to 14 weeks and can be used to work out how many weeks pregnant you are and your due date.^[12] If you have not yet started local booking, week 8 is a sensible time to do that through your own GP, midwife, maternity service, or local system.

Use our Due Date Calculator

Use the Due Date Calculator if you want an LMP-based due-date estimate using the 40-week convention. For the month conversion, open 8 weeks pregnant in months. For a wider first-trimester summary, read First Trimester Week by Week.

Week 8 often becomes a planning week as much as a development week. Some readers are starting to think about booking appointments, work schedules, family timing, or how far away the dating scan may be. NHS windows are useful anchors; your own maternity, GP, midwife, or local health system may give different operational instructions.

What's next

Read 7 weeks pregnant for the previous week, or continue to 9 weeks pregnant. For the full map, return to the Pregnancy Week by Week hub. For a wider overview, see First Trimester Week by Week.

Sources