Whether it is planned or not, discovering that you are pregnant can be an incredible but sometimes overwhelming experience.

It is easy to think, from the many depictions of pregnancy in the media, that life can go on pretty much as normal.

However, many people find the early weeks of pregnancy, during the first trimester, some of the most difficult, as the body undergoes some pretty drastic changes, to prepare itself for the nine months ahead.

What is the first trimester?

Let’s start with some jargon-busting.

Full term pregnancy lasts around 40 weeks.

And it is commonly split up into three stages, or trimesters:1

First trimester

This is the period during weeks 1 to 12.

Second trimester

This is the period during weeks 13 to 27.

Third trimester

This is the period during weeks 28 until birth.

Pregnancy is worked out from a calculation from the first day of your last period and not from ovulation.

You can use online due date calculators to work out which week you are in.2

Early signs of pregnancy

Of all the first signs of pregnancy, most people usually notice the absence of a period first.

Because of the way the due date is calculated, symptoms usually do not start until you are at least 3 weeks pregnant or more.

Before 6 weeks pregnant, you might experience some of the very early signs of pregnancy, including:3
  • Tender breasts
  • Nausea and vomiting
  • Changes in toilet habits, including discharge
  • Extreme tiredness
  • Changes in smell and taste, including food cravings
You might also be interested in our Health Hub article, ‘What happens in the early days of pregnancy?

6 weeks pregnant

At 6 weeks pregnant, the embryo measures around 6mm long.4

You are still likely to be experiencing some or all of the early signs of pregnancy as the hormones increase in your body.

That said, some people do not experience pregnancy symptoms and still may not know they are pregnant at this point.

7 weeks pregnant

At 7 weeks pregnant, the embryo is around 9mm long.5

If you are experiencing nausea, vomiting and cravings, you might not want to think about food, but if not, this is a good time to think about dietary changes that you might need to make.

For more info, check out Health Hub articles, ‘What foods should I avoid during pregnancy?’ and, ‘Why good nutrition matters during pregnancy

8 weeks pregnant

Just under 20mm long, your baby is still pretty tiny. However, its skeleton is fully formed, but only in cartilage, not bone yet.6

You are already two months into your pregnancy at this point; just over seven to go!

You are likely to still be experiencing tiredness, nausea and all the other early signs. Look after yourself and keep going!

Gentle exercise may well help alleviate some of the symptoms, and it will certainly help your body and growing baby.

9 weeks pregnant

The foetus’ skeleton is changing from cartilage to bone, and most of the internal organs have formed.

It can move its arms and legs now!7

10 weeks pregnant

At 40mm long, your baby is really growing fast.8 If you have suffered with extreme fatigue, you might have noticed some changes in your mood too.

Be kind to yourself and try to give yourself rest periods: you are growing a human inside you!

11 weeks pregnant

You are nearly done with the first trimester, but there is one symptom of pregnancy that could strike at any time: perinatal depression.

If you find yourself struggling with daily tasks, low mood, feeling alone or detached, make sure you talk to your midwife or GP, who can refer you for help.9

12 weeks pregnant

You have done it! You have reached the end of the first trimester.

Your baby is around 70-80mm long.10 You should be having your first scan this week.

Rest assured that most people start feeling much better in the second trimester, as the signs of early pregnancy subside and energy levels rise.

Not that there are not plenty of second trimester symptoms to think about…

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Last updated: 18 December 2020

Andrea Dobronszki

Author: Andrea Dobronszki, Senior Regulatory Affairs Associate

Joined Holland & Barrett: Aug 2020

Master’s Degree in Food Science and Technology Engineering and BSc in Dietetics

Andrea started her career as a clinical dietitian and lecturer at a university hospital, managing the dietetic treatment of patients with various diseases, and giving lectures in nutrition for medical students.

Later she worked as a Product Developer at a sport nutrition company where she developed food supplements and fortified foods, and ensured that the products complied with the relevant regulations.