All You Need To Know About Pregnancy Trimesters

1 mins to read

Discover more about your baby’s key developmental milestones, and the important nutrients that help them on their way.

Pregnancy and preconception

Healthy eating in pregnancy

Foods rich in essential nutrients are an important part of a normal diet and eating a healthy diet is especially important during pregnancy.

A balanced diet and good nutrition can help to support the health of both you and your developing baby to.

There are certain nutrients that have an increased requirement during pregnancy and at different pregnancy stages.

Here we highlight some key pregnancy vitamins and mineral requirements during each pregnancy trimester.

The first trimester

The first trimester is calculated from the first day of your last period (usually two weeks before you actually conceive) to the end of week 12.

Although you probably won’t look pregnant yet, you may experience early pregnancy symptoms such as nausea, fatigue, aches and cravings.

The first trimester is a key developmental stage for your baby, who goes from being a zygote (a fertilised egg cell) to an embryo smaller than a grain of rice, to a foetus with recognisable form.

Incredibly, all its bodily organs are usually formed by week 10, although it’s still only about 2.5cm long.

As well as limiting or abstaining from potentially harmful substances such as caffeine and alcohol, the first trimester is a crucial time to monitor your intake of dietary folate - also called folic acid. This B-group vitamin is essential to the development of your baby’s neural tube, which will later form the brain and spinal cord.

The neural tube is formed and closed in the first four to six weeks of pregnancy, and it’s recommended you take a supplement with at least 0.5 mg (500 µg) of folate (during your first trimester to reduce the risk of neural tube defects such as spina bifida.

The second trimester

The second trimester is from week 13 to the end of week 26.

Your baby will likely develop vocal chords, taste buds and hearing, as well as eyelashes, eyebrows and fingernails.

As your baby grows and its soft, cartilage-like bones begin to harden, it’s especially important to eat foods that are rich in calcium and vitamin D.

The recommended daily intake of calcium for women increases form 840 mg to 100 mg during pregnancy to allow for the needs of mum-to-be and her developing baby.

Dairy products, as well as fish with edible bones such as sardines, and green leafy vegetables, are good sources of calcium.

Oily fish and fortified breakfast cereals are good sources of vitamin D, as is a daily dose of safe sun exposure.

The third trimester

The third and final trimester is from week 27 to the end of the pregnancy.

Your due date will be calculated as week 40, but your baby is considered full-term at 37 weeks and is most likely to be born between week 38 and week 42.

By week 33, your baby’s brain and nervous system are fully developed and bones (except for the skull – which remains soft for delivery through the birth canal) are continuing to harden. The third trimester is where your baby’s uptake of calcium is highest so keep up your intake of calcium-rich foods.

The lungs develop rapidly in the third trimester, and are usually fully formed at 36 weeks.

As well as being important in early pregnancy, iron is essential during the third trimester as you’ll make more blood as you approach full-term (the average woman will have five litres of blood pre-pregnancy and seven to eight litres close to her due date).

Sources of iron include red meat, chicken and fish. Vegetarian (non-haem) sources include nuts, legumes, dried fruit, green leafy vegetables and beetroot.

To help absorb more iron from your food, eat vitamin C-rich fruit and vegetables at the same time.