1-4 weeks pregnant: early signs and symptoms of pregnancy

During weeks one to four of your pregnancy, your body is already going through some significant and incredible changes.

Here we’re looking at some of the early signs of pregnancy, the various body changes you might experience, and your baby’s growth and development during their first few weeks in the womb. You’ll also find some helpful information about early pregnancy diet to support you and your baby's health.

Remember that every pregnancy is different. Your experience is unique to you. Whilst some women will experience several early pregnancy symptoms, others will experience very few or none at all. If you’re concerned about any symptoms, always speak to your midwife or GP for advice and reassurance.

Signs of Early Pregnancy

Early signs of pregnancy can include several things, but the most obvious is a missed period. In the early weeks of pregnancy, you might experience some light early pregnancy bleeding or ‘spotting’, also known as implantation bleeding, around the time your period is due.

Other early signs of pregnancy include:

• Feeling more tired than usual.
• A change to your sense of smell and taste. For example, some women experience a metallic taste in early pregnancy.
• A change in your usual toilet habits. You may find yourself going for a wee more often or experiencing constipation.
• Sore or tender breasts.

Morning sickness is also a common and well-known early pregnancy symptom, although this usually doesn’t start until around weeks four and six of your pregnancy.

Your baby’s growth at 1-4 weeks pregnant

Whilst there’s not much to see in the first few weeks of your pregnancy, exciting changes are already happening, and they’re doing so rapidly. 

Fertilisation takes place approximately 14 days after the start of your last period, and from this point, the fertilised egg is known as a Zygote. In the 90 days after fertilisation, the cells divide until they’re a solid mass, which then makes its journey from the fallopian tubes to your uterus.

Around 5 to 10 days after fertilisation, you may notice some light ‘spotting’. This is called implantation bleeding and can be one of the signs of early pregnancy. It’s nothing to worry about and is the result of the developing embryo (technically known as a blastocyst) attaching itself to the wall of your womb, where it will continue to grow and develop.  It’s also completely normal to not have any implantation bleeding.

The embryo is protected by an amniotic sac filled with fluid that will cushion your baby throughout your pregnancy. 

As it develops, rapidly multiplying cells form distinct layers within the embryo. These will soon become your baby’s internal organs, the skeleton and muscles; brain; nervous system; and external body parts, such as skin, eyes and nails.  The outer layer will later develop into the placenta and provide your baby with oxygen and nutrients.

Although it’s still very early in your pregnancy, and whether you’re experiencing any early pregnancy symptoms or not, your baby already has the basic building blocks of their body in place. After four weeks, your baby is still tiny, measuring about 2mm long, about the size of a poppy seed.

Your placenta in early pregnancy

In the early weeks of pregnancy, the amniotic sac holding your baby is attached to a tiny yolk sac, which provides the developing embryo with the nourishment it needs.

Very soon, your placenta will begin to form, but it won’t be fully developed until around week 12 of your pregnancy. This life-sustaining organ will supply your baby with the oxygen and nutrients they need to grow. It also passes antibodies to your baby during the last three months of pregnancy, providing it with essential resistance to infection.

Another function of the placenta is hormone production.  These hormones help your baby grow and develop while supporting your physical changes from the earliest stages of pregnancy. Progesterone and relaxin, for example, both have a relaxant effect on your muscles, allowing your uterus to adapt and make room for your growing baby. 

Early Pregnancy Diet

Whilst you don’t need to follow a particular diet in early pregnancy, eating a variety of foods every day is a great way to ensure you and your baby are getting the nutrients you need.

A healthy and balanced diet in the first weeks of pregnancy includes:

• Plenty of fruit and vegetables. These will provide fibre and essential vitamins and minerals, including vitamin C which helps to increase iron absorption.
• Dairy products or dairy alternatives such as low-fat milk, cheese, yoghurt and unsweetened  calcium-fortified soya milk (if you don’t drink regular milk) to make sure you’re getting enough calcium.
• Carbohydrate-based foods such as potatoes, rice and pasta (eating wholegrain varieties will provide extra fibre intake).
• Foods that are rich in protein. For example, lean meat, fish, eggs, pulses, and lentils.

Vitamin C is a vital nutrient in the first four weeks of pregnancy. As your body adjusts and prepares to support your baby, it contributes to normal collagen formation, which is important for the normal function of blood vessels.

The Recommended Dietary Allowance (RDA) of vitamin C during pregnancy is 60mg per day. A large strawberry provides around 14mg.

An equally important role of vitamin C is to increase the absorption of non-haem iron (the iron found in plant sources such as spinach) into your bloodstream. Iron is a key component of your blood, helping to transport oxygen around your body and to your baby. A healthy supply of this mineral is essential for your baby’s normal cognitive function.

Next steps

Why not try adding one of the following vitamin C-rich foods to your mealtimes to increase your absorption of iron? For example:

• Steamed broccoli.
• Raw spinach.
• Brussels sprouts.
• Tomatoes.
• Peppers.

You’ll also find plenty of vitamin C in fruits such as strawberries, blueberries and kiwi fruit.