3 weeks pregnant: Symptoms, advice, and what to expect


by Lorna White |

At three weeks pregnant, it is time for the sperm to meet the egg. As we mentioned in week two, your partner’s sperm goes on a very difficult journey to fertilise your egg, but if it’s made it and you’ve conceived, this is the week when your baby will first start to form.

At week three, you're in the first month of your pregnancy and you still have eight months to go until you can meet your little baby!

Pregnancy symptoms week 3

What symptoms and signs of pregnancy do you need to look out for in these early days and weeks?

A heightened sense of smell

Abdominal pressure (like period cramps)

• Metallic taste in mouth

• Nausea/morning sickness

Implantation bleeding

Missed period

Tender and sore breasts

Positive home pregnancy test

While some people don't feel any changes or symptoms at all in this early stage of pregnancy, some can feel the above. But don't worry if you're not experiencing any symptoms just yet. Every body is different and your symptoms can soon change in this early stage.

How big is my baby at three weeks pregnant?

Right now, your baby has transformed from a fertilised egg (a single cell called a zygote) to a ball of around 100 cells about the size of a pinhead. This ball of cells is officially referred to as a blastocyst.

3 weeks pregnant belly

As it's so early and your baby is so tiny, you won't have a belly or bump just yet, although you may be feeling bloated. Many women don't show until they reach the 12 week mark, so you've still got a way to go until you can admire your pregnant belly.

What is my baby doing?

Within hours of being fertilised, your tiny egg will start to travel from your fallopian tube to your uterus, and the fertilised egg (now medically referred to as the zygote) will divide into 16 identical cells.

This journey can take up to six days, so implantation probably won’t happen until week four.

The inside of the cell mass will become the embryo itself and the amniotic sac. The outer cell mass will become the placenta.

3 weeks pregnant ultrasound

Your tiny fertilised egg is now on its way to your uterus, ready to implant - yay! Although it's a super exciting time, your baby won't show up yet on an ultrasound scan.

What's happening in my body?

From the outside, it probably won’t feel like much is happening right now, but if you’ve timed things right, that precious blastocyst is starting out on its journey and heading for your uterus.

Just after the egg is released from the follicle it came from, it will be replaced by a yellow group of cells called the corpus luteum.

This, in turn, produces enough of the pregnancy hormones progesterone and oestrogen, to support your future baby for the next ten weeks, until the placenta is ready to take over.

At this point, you still probably won’t get a positive pregnancy test, but in the next few weeks, once the blastocyst has made its way into the uterus, the cells of the developing placenta will make human chorionic gonadotropin (hCG). This surges in your first trimester and tells your ovaries to stop producing eggs and start making more progesterone and oestrogen.

Once hCG is in your system, home pregnancy tests will pick it up - some home tests these days are sensitive enough to be able to give a positive result after as little as 3 or 4 weeks of pregnancy.

The amount of pregnancy hormone hCG in your body may not yet be high enough for a pregnancy test to detect it.

However, the hormone doubles every 48 hours and if you get a negative result you can always take a second a few days later.

3 weeks pregnant test

What should I be doing at this stage?

You need to make sure you are eating healthily and getting the right nutrients and vitamins when trying to conceive or during the early stages of pregnancy.

Up the protein: Your baby will need extra protein to help it grow, so try and make sure you get three servings of protein a day in these first few weeks.

Make sure you’re getting enough calcium: It might seem obvious, but if you’re not getting enough calcium in your diet when you’re pregnant, your baby will start taking it from your bones! Now’s the time to up the intake – foods like Greek or frozen yoghurt will help. If you’re still struggling, it might be worth looking for a calcium supplement.

Avoid getting your hair dyed: It's a good idea when you're pregnant to avoid having any sort of chemicals touch your scalp. Talk to your hairdresser about chemical-free alternatives they can recommend.

Read more: Your go-to guide to taking supplements while pregnant

Things to think about this week...

Work out your due date

If you're having trouble working it out on your fingers, try out our due date calculator. All you need to know is the first day of your last period and how many days your menstrual cycle is!

Educate yourself!

It's time to start reading all about what to expect in your first trimester. You'll find out what your body and your baby will be doing in the next 12 weeks!

Keep taking your vitamins

Taking prenatal vitamins will benefit your baby's development and nourish your pregnant body and health. Adding a supplement of 400 micrograms of folic acid to your diet will help the foetus to develop healthily.

Go back to 2 weeks pregnant

Jump to 4 weeks pregnant

Popular articles to read next

The best pregnancy apps for you and your growing bump

The most popular food cravings and aversions during pregnancy (and their meanings!)

When is morning sickness considered hyperemesis gravidarum? And can you have it without vomiting?

Just so you know, whilst we may receive a commission or other compensation from the links on this website, we never allow this to influence product selections - read why you should trust us