Early Signs & Symptoms of Pregnancy: 1-4 Weeks

Reviewed by Deborah, an experienced midwife and public health specialist (MPH). Dedicated to evidence-based care, Deborah draws on her clinical expertise to advocate for women and families across the UK maternity system.

Even though the first signs of pregnancy may not be obvious just yet, there’s plenty going on inside your body. In fact, your baby is developing faster now than it will at any other point during your pregnancy³.

Here’s what’s happening for your baby at this early stage^1,3:

• Your newly fertilised egg is made up of a single cell called a zygote.
• Around 90 hours after fertilisation, the cells within the zygote begin dividing, forming a tiny mass known as a blastocyst.
• The blastocyst travels from your fallopian tubes to your uterus, where it will implant itself into the lining of your womb to grow and develop.
• Once it reaches the uterus, your baby will be called an embryo.

It’s not uncommon to experience some light spotting or bleeding at around this time. This is called implantation bleeding, and can be one of the very early signs of pregnancy in week 1⁴, around the time your period would have been due. If you are unsure about any bleeding during pregnancy, contact your midwife or GP.

This early on in your pregnancy, your newly fertilised egg is made up of a single cell called a ‘zygote’⁽¹⁾. Around 90 hours after fertilisation, the cells within the zygote will divide, and will continue to do so until they form a tiny mass known as a blastocyst. This will then travel from your fallopian tubes to your uterus, where it will implant itself into the lining of your womb to grow and develop⁽¹⁾. Once this happens, your baby will be referred to as an embryo⁽²⁾. 

It’s not uncommon to experience some spotting or light bleeding at around the same time your period would have been due, and this is known as implantation bleeding⁽³⁾.

Although the early signs of pregnancy (except for perhaps some implantation bleeding) may not have kicked in just yet, there’s plenty going on. In fact, your baby is developing faster now than it will at any other point during your pregnancy⁽⁴⁾.

At 4 weeks pregnant, your baby will be around the size of a poppy seed, measuring just 2mm long².

Right now, they’re protected by the amniotic sac, which is filled with cushioning fluid. This is attached to a tiny yolk sac that will give your baby the nourishment they need for now. Later on, the outer layer of the sac will become the placenta, providing your baby with vital oxygen and nutrients as your pregnancy progresses².

Everyone pregnancy different. Whilst some women experience 1-4-week pregnancy symptoms, others won’t experience any pregnancy signs until later in the first trimester. There's really no way to tell what your experience will be.

Here are some of the first signs of pregnancy that you could experience at this stage.

At this point in your pregnancy, it’s unlikely that you’ll look pregnant or have a noticeable baby bump. Most first-time mums don’t start showing until at least week 12, at the end of the first trimester¹³. However, if you’ve been pregnant before, you may start showing a little sooner, as the muscles in your uterus have been stretched by a previous pregnancy.

By week 4, your body is starting to grow the placenta, a brand-new organ that will supply your baby with the oxygen and nutrients needed to grow and develop. The placenta ensures that antibodies are passed to your baby, helping them strengthen their immune system in the final stages of pregnancy^2,14.

The placenta also produces hormones to support your baby’s growth and development in the womb, and the physical changes happening to your body¹⁵.

You won’t need to follow a special or particular diet during your pregnancy unless you’ve been advised to do so by your doctor or midwife¹⁶. The important thing is to eat a variety of different foods every day, as that’s the best way to ensure that you and your baby are getting all of the vitamins and minerals you need.

From the moment you find out that you’re pregnant, or if you’re trying for a baby, there are certain foods that you’ll need to either avoid entirely or reduce the amount you eat.

This includes things like¹⁷:

• Raw and uncooked meat.
• Unpasteurised milk and certain cheeses.
• Foods that contain a high level of vitamin A.

It’s also important to ensure that you’re taking a folic acid supplement every day - the recommended intake is 400mcg. Folic acid supports the development of your baby’s nervous system and can help to protect against spina bifida¹⁸. We cover the importance of folic acid in more detail in week 5.

Eating a varied and balanced diet during pregnancy will help ensure you and your baby get all the nutrients you need, including vitamin C and iron.

Getting enough iron in your diet during pregnancy is important for energy and preventing anaemia, while vitamin C protects your cells, keeping them healthy¹⁸.

Most people can get all the iron and vitamin C they need from their diet, without needing to take a supplement. Sources of vitamin C and iron include:

It’s unlikely that you’ll feel pregnant before you miss a period, especially if your menstrual cycle is regular and reliable. You’re more likely to start experiencing some of the early signs of pregnancy when the ‘pregnancy hormone’ human chorionic gonadotrophin (hCG) starts to become active, usually about 2 weeks after you conceive²⁰.

Most home pregnancy tests will provide a reliable result from the first day of your missed period. If your menstrual cycle is irregular, then the NHS advises that you take a pregnancy test 21 days after having unprotected sex²¹.

When it comes to which pregnancy test to use, there are plenty of choices available. As long as you use them correctly and follow the instructions, home pregnancy tests are accurate and reliable.

You can make an appointment to see your doctor or midwife as soon as you find out you’re pregnant²¹. That way, you can ensure that you’re getting the antenatal care you need for a healthy pregnancy as soon as possible.

The first appointment with your midwife is known as a ‘booking appointment’ and will usually happen before you reach week 10 of your pregnancy²². During the appointment, your midwife will ask you some questions to learn more about you and your circumstances. You’ll also have the opportunity to ask any questions that you might have, including any about your early pregnancy symptoms.

It’s unlikely that you’ll gain much weight at all in early pregnancy. Most of the weight you’re likely to gain will come on after week 20, when your baby is bigger, and your body’s storing fat to make breast milk²³. Over the course of your pregnancy, you could gain 10-12.5kg (22-28lb), but this varies greatly from person to person.