Your week 4 guide

Implantation connects the developing pregnancy to your blood supply for the first time. Until now the cluster of cells has lived on its own reserves, and burrowing into the lining is what gives it access to oxygen and nutrients from you. This is also the moment hCG production begins, which is why a test can finally read positive.

The amniotic sac and yolk sac begin to form. The amniotic sac will fill with fluid and become the cushioned space your baby floats and moves in, while the yolk sac supplies nourishment and makes the first blood cells until the placenta is ready to take over. The yolk sac shrinks away later, having done its job in the weeks before anything else could.

Cells are sorting themselves into three layers that will become every organ in the body. This organising step is what makes the coming weeks possible, and it is also why weeks four to ten are the period when developing structures are most sensitive to certain medicines and chemical exposures. It is a reason to check what you take, not a reason to comb back through everything you have already done.

A missed period is often the first unmistakable clue. For women with regular cycles it is the clearest early signal there is, though a late period alone can have other explanations. If your cycles are irregular, this signpost may be less useful to you, and an early dating scan may be offered instead.

Bloating, tender breasts, tiredness, mood shifts or light spotting can all appear now. Rising progesterone slows digestion and can leave you feeling puffy and unusually flat, and some women notice a small amount of pink or brown spotting around implantation. Any bleeding is still worth reporting so that it can be recorded and checked rather than guessed at.

Some women feel completely normal at four weeks, and that is not a bad sign. Symptoms depend heavily on individual hormone levels and sensitivity, and their absence this early tells you almost nothing. If you have had a loss before, this silence can be frightening rather than pleasant, and it is a fair thing to tell your midwife so you can be supported properly.

Take a home pregnancy test once your period is late, using first-morning urine for the clearest result. Testing at this point gives hCG time to reach a detectable level, so a positive is reliable and a negative is worth repeating in a few days. Read the result inside the time window on the packet, because marks that appear much later are not dependable.

Contact your midwife, GP or maternity service to arrange antenatal care as soon as your test is positive. Booking appointments often need to happen before ten weeks so that early blood tests and screening can be offered in time, and in many places waiting lists mean the call matters more than the appointment date. You do not need to have any questions ready to make it.

Take your current medicines and supplements to a pharmacist or clinician and ask what stays and what changes. Some medicines are switched in pregnancy, some continue exactly as they are, and a few over-the-counter products and herbal remedies are less benign than they look. Do not stop anything prescribed for a long-term condition before you have had that conversation. InshaAllah, one clear conversation can make the medicine list feel less daunting.

Food safety starts early: Pregnancy food-safety guidance applies from the earliest weeks. Some foods carry a greater risk of infection, excessive vitamin A or high levels of mercury.

Pay particular attention to raw or undercooked foods, unpasteurised dairy, liver and liver products, and high-mercury fish. Because the specific rules differ between countries, follow the food-safety guidance issued where you live rather than advice written for somewhere else.