What to Expect in the First Weeks of Pregnancy

The first weeks of pregnancy are a time of profound change — most of it invisible from the outside, but extraordinary at the cellular level. Whether this is your first pregnancy or a subsequent one, knowing what is typical can help you feel more at ease.

Very Early Pregnancy: Weeks 1–4

In a strict medical sense, "week 1" of pregnancy begins on the first day of your last menstrual period — before conception has even occurred. Conception typically happens in week 2 (around day 14 of a 28-day cycle), when sperm fertilises an egg.

Over the following days, the fertilised egg travels down the fallopian tube and divides rapidly, forming a blastocyst. By around day 6–10 after fertilisation (weeks 3–4 of pregnancy), the blastocyst implants in the lining of the uterus.

Most women do not yet know they are pregnant at this stage.

Finding Out You Are Pregnant: Weeks 4–5

Home pregnancy tests work by detecting the hormone human chorionic gonadotropin (hCG) in urine. hCG rises rapidly after implantation. Most tests are reliable from the day of a missed period (around week 4), and sensitive tests can detect pregnancy a few days before.

A positive test is exciting and may be accompanied by mild symptoms:

• Breast tenderness or fullness
• Slight bloating
• A missed period
• Possible light spotting (implantation bleeding) — this is normal and not a sign of miscarriage

Weeks 5–8: Symptoms Intensify

This period is often when pregnancy symptoms become more noticeable:

• Nausea is very common — affecting around 70–80% of pregnant women. It can occur at any time of day, not just morning.
• Fatigue may be significant. Your body is producing a new organ (the placenta) and dramatically increasing blood volume.
• Frequent urination begins early as the uterus grows and hormones affect kidney function.
• Food aversions and cravings are common and thought to be driven by hormonal changes.
• Heightened sense of smell can make nausea worse.

Internally, the embryo is developing rapidly. By week 6, a heartbeat can sometimes be detected on an ultrasound. By week 8, the embryo has recognisable limb buds and facial features are forming.

Weeks 9–12: Towards the End of the First Trimester

For many women, nausea begins to ease towards the end of the first trimester. The embryo is now called a fetus from week 10. By week 12, the fetus has all major organs in place and is approximately 5–6 cm long.

This is also the period when most women have their booking appointment with a midwife and, around weeks 11–14, their first ultrasound (the dating scan).

When to Contact a Midwife or GP

Contact your healthcare provider promptly if you experience:

• Heavy bleeding (a small amount of spotting in early pregnancy can be normal, but heavy bleeding should always be assessed)
• Severe abdominal pain, particularly one-sided pain (which could indicate ectopic pregnancy — a medical emergency)
• High fever
• Severe vomiting that prevents you from keeping any food or fluids down (hyperemesis gravidarum)

Don't wait for your booking appointment if you have urgent concerns — your GP or maternity assessment unit can see you sooner.

This guide is for general information only. Always contact your midwife or doctor if you have concerns about your pregnancy.