Week by week pregnancy guide: 1, 2 and 3 weeks pregnant

Once you know you're expecting, you'll probably want to track your pregnancy week by week (opens in new tab), so you can keep on top of all the things going on in your body.

In your very early weeks of pregnancy there won't be much to physically see or feel, but it's nice to know what's going on none the less.

In fact, you probably aren't even 'officially' pregnant at all in the first couple of weeks, but science tells us to count weeks of pregnancy from the first day of the last period. We've rounded up what to expect in your first three weeks, here's the low down...

What to expect: 1 week pregnant

Your 40-week pregnancy is dated from the first day of your period even though you haven't conceived yet. Actual conception will take place around midway through the month and it won't be until you miss your period that you'll be able to find out for definite that you're pregnant, around week 5 or your pregnancy.

As women ovulate at different times according to their cycle, dating your pregnancy this way gives carers a better idea of the due date. Your baby may just be 'a twinkle in their daddy's eye', but there are things you can be doing to make sure they're healthy.

Eat a well-balanced, nutritious diet and if you haven't been taking a daily 400mcg folic acid tablet you should start now and continue taking it up to week 12 of your pregnancy. This will significantly reduce the risk of your baby having spina bifida or other neural tube defects.

A study by the University of Surrey found that a better diet and lifestyle can boost your chances of conceiving by up to 80 per cent. Common offenders for preventing pregnancy are caffeine, alcohol and nicotine, so try and kick these first. And remember that means your partner, too.

What to expect: 2 Weeks pregnant

If you have a 28-day menstrual cycle you'll usually ovulate around day 14 (whatever the length of cycle, most women tend to ovulate around 12-16 days before their next period.) Your egg will survive for 12-24 hours after it's released from the ovary, so fertilisation has to happen within this time. You can also test if you are ovulating by measuring your temperature as your increases in temperature by three degrees.

What to expect: 3 weeks pregnant

250 million sperm have gone racing to your egg. When your partner's sperm meets your egg the life of your new baby begins. Within 30 hours of conception the newly-fertilised egg, now known as a zygote, undergoes the first division to form two cells. This is the first of billions of divisions and changes that will take place within the first few weeks of pregnancy.

Right now you probably won't feel the monumental changes taking place inside. However, your amazing body has already switched into overdrive in order to create a friendly environment for the newly-fertilised egg.

It does this by producing a pregnancy protein known as Early Pregnancy factor (EPF), an immunosuppressant which will stop your body from rejecting your growing zygote, which is roughly 1cm long.

At this point the dividing ball of cells is heading steadily along the fallopian tube towards the cavity of the womb. Once there it will implant by attaching itself to the wall of the womb. This journey to the womb takes about a week.

Some women start to feel pregnant around this time but there are some other early symptoms of pregnancy (opens in new tab) you should look out for.

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