You are 5 weeks exactly

At this important stage of development, the building blocks of your baby's spine are being laid down.

245 days until your due date

By the end of this week, the individual parts that will form the embryo have started to develop. Starting at the head end, segments called somites form, with about three new pairs appearing each day. Each one forms part of the baby's spine and the muscles of that segment of the body. Eventually there will be 4 somites at the head, 8 in the neck, 12 at chest level, 5 in the lower back (lumbar region), and 5 in the pelvis.

More somites develop below the pelvis, but most of them disappear. In other mammals, these go on to form the tail.

Explainer

Exercise and your baby

Regular moderate aerobic exercise in pregnancy, such as walking or running, burns excess fat but won't affect your baby's development.

Ask a Nutritionist

I'm underweight. Could this affect my pregnancy?

You may be more likely to have nutritional deficiencies, which could affect your baby's health, and more likely to give birth early to a smaller-than-average baby who is more vulnerable to health problems.

To gain weight, eat bigger portions of healthy foods with plenty of protein, good-quality fats, and unrefined carbohydrates. Choose nutrient- and calorie-dense foods such as avocados and whole-milk dairy, and eat lots of leafy greens for key vitamins and minerals. Snack on nuts, fruit, and seeds, and don't skip breakfast. Your doctor will refer you to a dietitian if needed.

Focus on

Your body: Your metabolism

Regular exercise raises your basal metabolic rate, the rate at which your body burns calories. Your metabolism is already slightly higher in pregnancy. Exercise encourages your body to use up excess energy and fat reserves, but it will always keep enough in reserve for your baby's growth. Exercise also helps regulate your blood sugar and energy levels.

This is general information based on NHS guidance, not medical advice, and every pregnancy is different. Talk to your midwife or GP about anything that worries you. If your baby's movements slow down or change, or you have bleeding, severe pain or leaking fluid, call your maternity unit straight away. In an emergency, call 999.