Pregnancy explained: trimesters and antenatal care

The first trimester (weeks 1 to 12)

The first trimester covers roughly the first 12 weeks. This is when the pregnancy becomes established and the baby's main organs begin to form. Many people feel very tired, and pregnancy sickness and tender breasts are common. It is also when you should tell your GP or midwife you are pregnant so care can begin — this is called booking. Taking folic acid is important in early pregnancy to help the baby's spine develop properly, along with vitamin D; a midwife or pharmacist can advise. It is wise to avoid alcohol and smoking, and to check that any medicines you take are safe in pregnancy. Miscarriage is most common in these early weeks, which is one reason early care and support matter.

The second trimester (weeks 13 to 27)

The second trimester is often the most comfortable stage. Early sickness and tiredness usually ease, energy often returns, and many people start to feel more like themselves. The bump becomes more visible, and around the middle of pregnancy you may begin to feel the baby move — a reassuring milestone. This is when a detailed scan is usually offered to check the baby's development. Your midwife continues to monitor your blood pressure and general health at appointments. It is a good time to plan practical things, learn about labour and birth, and look after your body with gentle activity and a balanced diet. Any bleeding, severe headaches, or a noticeable change once you feel regular movements should always be checked.

The third trimester (weeks 28 to birth)

The third trimester runs from around 28 weeks until the birth. The baby grows quickly and gets into position for labour. Common feelings include backache, heartburn, swollen feet, breathlessness and disturbed sleep as the bump grows. Antenatal appointments become more frequent to keep a close eye on you and the baby, including checks on blood pressure, growth and the baby's position. Getting to know your baby's usual pattern of movements is important — if movements slow down or change, contact your maternity unit straight away, at any hour. This is also the time to prepare for the birth, pack a bag, and know the signs of labour. A full-term pregnancy is usually reached at around 37 to 42 weeks.

How NHS antenatal care works

In the UK, antenatal care is free and led mainly by midwives, with doctors involved when needed. Care starts with a booking appointment, ideally before 10 weeks, where your health and any risks are reviewed and a plan is made. You are offered a schedule of appointments through pregnancy — more if you or the baby need closer monitoring. Routine checks include blood pressure, urine tests, and measuring the bump, along with blood tests and scans offered at set points to check your health and the baby's development. You will be offered screening tests, which are your choice. Your midwife is your main point of contact for questions, and your maternity unit and NHS 111 are there for urgent concerns.

Staying healthy and warning signs

Simple healthy habits support a good pregnancy: eating a varied, balanced diet, taking recommended supplements such as folic acid and vitamin D, staying gently active, and avoiding alcohol and smoking. Food-safety advice helps you avoid certain foods that can carry infection. Rest matters, and so does looking after your mental wellbeing — tell your midwife if you feel persistently low or anxious. Certain symptoms need prompt medical attention: vaginal bleeding, severe or ongoing tummy pain, a bad headache with vision changes or sudden swelling of the face, hands or feet (which can signal raised blood pressure), a high temperature, waters breaking early, or reduced or changed baby movements. If in doubt, contact your midwife or maternity unit — it is always better to check.