At 3 weeks pregnant, it’s time for the sperm to meet the egg. As we mentioned in week two of pregnancy, the 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.
If you take a pregnancy test now it may show as positive result. However, if you test too soon you may get a false-negative pregnancy test. If this happens and you’re convinced you’re pregnant, or if a faint line on a pregnancy test shows up, we recommend taking another in a few days.
How many months is 3 weeks pregnant?
At three weeks pregnant you're in the first month of your pregnancy and you still have eight months of pregnancy to go until you can meet your little baby.
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 that within hours of being fertilised divided into 16 identical cells) to a ball of around 100 cells about the size of a pinhead. This ball of cells is officially referred to as a blastocyst. The inside of the cell mass will become the embryo itself and the amniotic sac. The outer cell mass will become the placenta.
What is my baby doing at 3 weeks pregnant?
Now your baby is a cluster of cells, it is busy multiplying and growing. It is also making the journey from your fallopian tube to your uterus ready for implantation in week 4 of pregnancy. This journey can take 5 or 6 days.
Your pregnancy symptoms at 3 weeks pregnant
There are a few pregnancy symptoms that you might start to notice at this stage, with some including:
A heightened sense of smell
Things that you may not have noticed before may start to smell a little stronger. The hormones HCG and estrogen strengthen the smell of everything wafting around, whether good or bad, and it can ramp up your morning sickness.
Abdominal pressure
Cramping in pregnancy can feel a little like period cramps and it’s actually a sign that everything is going right, not wrong. It could be the sensation of embryo implantation that you’re feeling, your uterus growing or the thickening of the uterine lining. All is in order, so don’t worry.
Metallic taste in mouth
If it tastes like you’ve just had some pennies in your mouth, rest assured you’re not going crazy. This is a very normal symptom which, again, is down to our hormones wrecking havoc on our bodies. It should improve during your second trimester.
Tender and sore breasts
This may feel like an exaggerated version of how your boobs feel before a period. Again, sore breasts are down to your hormones, and some women even notice their nipples going darker.
Implantation bleeding
This is a small amount of spotting which happens when the fertilised egg implants in your uterus. If you experience pain alongside this bleeding, call your GP, as this could be a sign of an ectopic pregnancy.
While some people don't feel any changes or symptoms at all in this early stage of pregnancy, or until they've missed a period, 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. The video below lists all the possible symptoms, or changes you might feel or experience at this stage.
Your body at 3 weeks pregnant
As it's so early and your baby is so tiny, you won't have a belly or bump showing just yet, although you may be feeling bloated. Many women don't show until 12 weeks pregnant, so you've still got a way to go until you can admire your pregnant belly.
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, the best 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.
Looking after yourself at 3 weeks pregnant
Eat healthy, nutritious food and snacks
Make sure you are eating healthily and getting the right nutrients and vitamins during the early stages of pregnancy. 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 too, otherwise your baby will start taking it from your bones. Foods like Greek or frozen yoghurt will help, but if you’re still struggling it might be worth taking a calcium supplement.
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. You can also take pregnancy vitamins, but check with your midwife before purchasing
Avoid getting your hair dyed
You may be wondering if you can get your hair dyed if you're pregnant and while there's still conflicting advice around this, if you're unsure, it's recommend to wait until after the first trimesters when the risk of chemical harm to your baby is lower.
Stop smoking
The NHS advises that when you suspect you might be pregnant then you should stop smoking. They say, "it is one of the best things you can do for your baby's health."
Avoid overheating
It is fine to have a lovely warm bath, especially pampering yourself with pregnancy bath products, but don't have it too hot. It is best to avoid hot tubs, saunas and steam rooms because a high body temperature is not good for baby, especially in early pregnancy.
Cut down on caffeine
Don't think you can't enjoy your morning coffee, but don't overdo it, or choose a caffeine free option. The NHS advises that you have no more than 200mg of caffeine per day during pregnancy.
Avoid alcohol
It is best to abstain from alcohol while pregnant, or if you suspect you might be expecting. However, don't panic if you have already had a glass or two, this is unlikely to cause any harm. You won't need to worry about missing out on your favourite tipple, there are lots of non-alcoholic drinks you can still enjoy.
Things to do at 3 weeks pregnant
Work out your due date
If you're having trouble working it out on your fingers, you can use a 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 and remember, you won't see your baby until your 12 week scan. That is why it will be good to read about their development week by week during pregnancy, as well as possible symptoms you might experience, while you wait.
Boy or girl?
You won't be able to find out if you are having a boy or girl until your 20 week scan. This is also known as your anomaly scan because the sonographer looks for foetal abnormalities as well as most likely being able to determine the sex of your baby (if you want to know). However, while you might have to wait to find out, at 3 weeks pregnant, whether you are having a baby boy or baby girl has already been determined at fertilisation. Of course, if you can't wait until 20 weeks then have a go at using the Chinese Gender predictor tool.
Lorna White is a Senior Digital Writer and has written for Mother&Baby since 2020. She has a keen interest in a range of topics, from potty training and nutrition to baby names and maternity fashion.