Knowing what to expect at 4 weeks pregnant, when you might still be wondering if you are pregnant or not, isn’t easy but your placenta and embryo have already begun forming a crucial alliance that will last 8 months.

At 4 weeks pregnant, your baby is currently just a blastocyst but has already completed an amazing journey from your fallopian tube through to your uterus. It then burrows its way deep into the lining of your uterine and makes itself comfortable.

An unbreakable connection is born in week 4 between you and your baby that will last the next eight months and for a whole lifetime.

What’s my baby doing at four weeks pregnant?

Embryo development

Your embryo starts to develop and grow from within the lining of your womb. It is here that the embryo cells form crucial links with mum’s blood supply, eventually forming into 3 different layers. 

All three layers will amazingly develop and grow to be the different parts of your beautiful baby’s body.

  • The inner layer will end up being the digestive and breathing platforms, which include your baby lungs, gut, bladder and stomach
  • Your baby’s heart and blood vessels will be formed from the middle layer
  • The brain, nervous system, tooth enamel, nails, and skin are all formed from the outer layer


Your embryo will be feeding in week 4 of your pregnancy from a small yolk sac, which provides all its nourishment. By week 6 of your pregnancy, your placenta will be fully formed and take over transferring nutrients directly to the embryo.

Once the placenta has taken over providing nutrients to the embryo, it starts to grow deep into the wall of the womb, so it can continue to provide a rich blood supply. it is this blood supply that ensures your baby receives the oxygen and nutrients it needs to grow over the next 8 months.

Changes in your body at 4 weeks pregnant

If you notice a missed period or you suspect you’re pregnant, always take a pregnancy test to be sure.

The symptoms of early pregnancy are similar to a period


If you feel bloated in the fourth week of your pregnancy, your hormones are to blame. When considering what to expect at 4-weeks pregnant, hormones are an important subject. There is a female hormone called progesterone, which relaxes the muscles of the uterus so that it can expand to house your little person over the duration of your pregnancy.

Light bleeding or spotting

Spotting at 4 weeks of a pregnancy is not uncommon and can be associated with a term called implantation. Make sure you keep a close eye on any type of bleeding. If the bleeding lasts more than a few days then it likely means that you haven’t missed your period. If bleeding lasts more than a few days and you had a positive test then see your GP immediately.


Pregnancy hormones can cause emotional feelings and even moodiness. You and your partner should be aware of some of the tactics available to alleviate these mood swings. Make sure you sleep well, eat the right foods, and don’t be afraid to ask your partner for a nice soothing massage.

Tender boobs

It’s amazing how quickly your boobs will start to prepare for their feeding duties. Your hormones will be surging in week 4 of pregnancy and it’s not uncommon for your milk ducts to start swelling.

Morning sickness

Morning sickness in week 4 of pregnancy can be hit and miss. Every woman and every pregnancy is individual and different. Some women report feeling only mild bouts of nauseousness, whilst others are vomiting daily! If you have morning sickness (which affects 6 out of 10 pregnant women) remember that it usually disappears during your second trimester.


Discharge is a normal symptom at 4 weeks pregnant. Do keep an eye on the colour of any discharge because it should be clear, and have no odour.

General fatigue

Another very common symptom at 4 weeks pregnant is fatigue. It’s normal to feel exhausted because your body is coping with the effort needed to home and feed a new person. You need to make sure you keep your levels of iron up during your pregnancy because fatigue can present itself due to iron deficiency. More than 15 percent of all pregnant women suffer from iron deficiency, so make sure you discuss this with your doctor.

Week 4 of pregnancy is also, surprisingly, when many women decide to take a pregnancy test and look into their ovulation dates.

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