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Pregnancy at weeks 1 to 4

3-minute read


Your baby

Your pregnancy is calculated according to the first day of your last period. In the first week of your menstrual cycle, and in the second week your ovaries release an egg (called an ovum). This is fertilised by your partner’s sperm sometime in the third week.

About 30 hours after conception, the fertilised egg divides into two. At this stage it is called a zygote. The cells keep dividing and multiplying in numbers and the zygote gradually moves down the fallopian tube towards the womb (uterus).

By the end of the fourth week, the egg implants itself into your uterus. It is now called a blastocyst. It is about 0.2mm wide and contains about 200 cells.

The blastocyst is made up of different layers of cells. The outer layer, called the ectoderm, will become the baby’s nervous system and brain. The middle layer, or mesoderm, will become the heart, blood vessels, muscles, and bones, and the inner layer, or endoderm will become the breathing and digestive systems. The outside of the blastocyst has small tentacles called chorionic villi, which will develop into the placenta.

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Your body

As soon as you conceive, the hormone levels in your body start to change. You produce more of the hormone progesterone, which prevents you from having a period, and there is an increase your levels of human chorionic gonadotropin (hCG). This is the pregnancy hormone that is detected when you do a pregnancy test.

You probably won’t notice any signs that you’re pregnant just yet. The first sign for many women is that they miss their period at the end of week 4.

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Things to remember

Your baby will have the best possible start in life if you make sure you are healthy when you conceive.

If you are trying for a baby, it’s a good idea to take 400 micrograms of folate every day to prevent neural tube defects such as spina bifida. If the baby is planned, you might consider seeing your doctor to talk about genetic screening or to be tested for any sexually transmitted infections before you fall pregnant.

You should try to eat a healthy diet and make sure you’re not overweight when you’re trying to fall pregnant. Not drinking alcohol and giving up smoking are best for your baby.

Read more here about preconception health.

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Your pregnancy journey

Click here for week 5


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Last reviewed: August 2019


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Need more information?

4 weeks pregnant: Key points

When you are 4 weeks pregnant your body and your new baby are undergoing rapid changes. The placenta forms and begins producing a hormone called human chorionic gonadotrophin (hCG), which is the substance a pregnancy test detects to confirm you are pregnant. The cells which are growing into your new baby establish membranes which connect them to the placenta and prepare themselves for differentiation into different types of cells, which will occur next week when you are 5 weeks pregnant. These developments may cause you to experience unusual emotions and also cause changes in your body such as darkening of the areolas of your nipples.

Read more on Parenthub website

5 weeks pregnant: Doctor appointments

Week 5 of pregnancy is the best time to have a pregnancy test. You can use a home pregnancy test but it’s still important to visit your doctor so that they can estimate your pregnancy due date. This may involve an early pregnancy ultrasound. You should also receive pregnancy health advice and discuss pregnancy folate supplements in the fifth week of pregnancy if you have not already done so. It’s also a good time to make sure you’re eating all the right pregnancy foods and start your pregnancy exercise routine.

Read more on Parenthub website

Week by week pregnancy- antenatal care at 7 weeks pregnant

Your doctor can look at your foetus’s features to determine how old they are – find out how. You need to talk to your doctor if you experience very severe morning sickness as you may not be getting all the nutrients you and your baby need or early pregnancy spotting (spot bleeding) as you may be at risk of miscarriage.

Read more on Parenthub website

8 weeks pregnant | Raising Children Network

8 weeks pregnant? In this pregnancy week by week guide, find out how your baby is growing, how your body is changing and how to look after yourself.

Read more on raisingchildren.net.au website

Pregnancy at week 12

By week 12, your baby is the size of a plum but fully formed, with their organs, muscles, limbs and bones in place.

Read more on Pregnancy, Birth & Baby website

Bleeding or pain in early pregnancy

One in 4 women will experience bleeding and/or pain during their first 12 weeks of pregnancy. Unfortunately half of these pregnancies may also end in miscarriage, which cannot be prevented.

Read more on WA Health website

2 weeks pregnant

When you are two weeks pregnant, your body is preparing for pregnancy but your egg has not yet been fertilised. Typically your egg will be released from your ovaries at the end of the second week of pregnancy and conception will occur on the first day of the third week of pregnancy. If you want to get pregnant, make sure you have plenty of sex this week so your partner’s sperm is ready and waiting to fertilise your egg.

Read more on Parenthub website

Pregnancy at week 10

Think about the prenatal screening tests you might have, and whether you want a dating scan to confirm your due date.

Read more on Pregnancy, Birth & Baby website

Pregnancy at week 32

Your baby doesn't have a lot of room, but they will still be moving. The extra weight might cause you some back and pelvic pain which can make it difficult for you to move around.

Read more on Pregnancy, Birth & Baby website

Ultrasound scan

Most women will have at least one ultrasound scan during their pregnancy. It usually takes place between 18 weeks and 21 weeks.

Read more on Pregnancy, Birth & Baby website

Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

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