Your week 18 guide

Myelin is beginning to coat the developing nerves so signals travel faster and more reliably. This fatty sheath works rather like insulation on a wire, and laying it down is what turns scattered nerve activity into coordinated movement. The process continues well past birth and into childhood, which is part of why newborn movements remain jerky at first.

The brain has produced billions of neurons over the first four months of pregnancy. Nerve cells are generated in vast numbers and then migrate to their correct positions, and many of those that fail to make useful connections are later pruned away. The refinement matters as much as the raw number.

Nerve endings and the tiny bones of the inner ear now let your baby hear your heartbeat, blood flow and digestive sounds. The womb is not quiet; it is full of the rhythmic, low-frequency sounds of your body. Voices reach through too, though muffled and stripped of higher tones, and this early exposure is part of why newborns respond to their mother's voice.

Bones are hardening through ossification, beginning in areas such as the collarbones and legs. Calcium is being deposited into the cartilage framework laid down earlier, which is why calcium intake matters throughout pregnancy rather than only at the end. The skull is deliberately left until last and stays flexible for birth.

Movement now includes twists, turns, stronger kicks and yawns. There is still plenty of room, so your baby can change position completely and often does. Yawning is thought to help develop the jaw and respiratory muscles rather than signalling tiredness.

You may start noticing movement, though the timing of first movements varies widely. Women in a second or later pregnancy usually recognise it earlier, simply because they know what they are feeling for. Where the placenta lies also matters, since a placenta at the front of the uterus cushions movement and can delay this by weeks.

Backache and muscle pain can increase as relaxin loosens your joints and your posture shifts. The centre of gravity moves forward as the bump grows, which tips the pelvis and loads the lower back differently. Strengthening work suited to pregnancy, decent shoes and sitting with support help more than rest alone.

Leg cramps, nosebleeds, varicose veins and disturbed sleep can all occur. Night cramps in the calf are common and usually ease with flexing the foot upward and gentle stretching before bed. Varicose veins result from increased blood volume and pressure from the uterus on the veins returning blood from the legs, and support stockings and moving regularly help.

Fluid retention may cause swelling in your hands or feet. Mild swelling that builds through the day and settles overnight is a normal part of later pregnancy. Sudden swelling, particularly of the face or hands, a severe headache, new blurred vision or other visual changes, or pain below the ribs can each be a warning sign of pre-eclampsia. Contact your maternity team immediately if any occurs; you do not need to have several symptoms together, and you should not wait for your next appointment.

Ask your care team whether your iron intake is meeting your needs. Blood tests taken at booking and again later in pregnancy are what actually answer this, and the results guide whether anything needs to change. Ask what your numbers were rather than accepting a general reassurance, particularly if you are vegetarian or have had low iron before.

Include calcium-rich foods regularly and keep taking the supplements recommended for you. Bone hardening is underway, and your baby draws calcium from your circulation, which is why intake matters for your own bones as well. If you avoid dairy, check that your alternatives are fortified, since many are not.

Protect sleep and adapt your exercise to your changing balance and shape. Side-lying with a pillow between the knees is more comfortable for most women from now on, and left-side sleeping is often suggested later in pregnancy. For exercise, reduce anything with a fall risk and expect your balance to be less reliable than it was.

Make time for your partner or the people close to you, and plan any celebration at your own pace. Pregnancy can quietly swallow every conversation, and deliberately talking about something else is worth protecting. If you want a baby shower, planning it loosely now avoids arranging it while heavily pregnant. Alhamdulillah for company that lets you be yourself, not only an expectant mother.

Keep protein varied: Protein supplies the amino acids used for growth and repair in both your body and your baby's developing tissues. It matters throughout pregnancy rather than in one particular growth week.

Sources include beans, lentils, chickpeas, eggs, dairy products, fortified alternatives, tofu, nuts, seeds, poultry, meat and suitable fish. Variety also brings a wider range of vitamins and minerals than concentrating on one favoured source.