Video: How do you calculate a due date?

How do you calculate a due date?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

When you calculate your due date, you're going to start with the first day of your last period, assuming you know when that was. We assume while calculating due dates that every woman has a 28-day cycle, so in fact when you have an ultrasound scan it may turn out that your due date is little bit different.

Your ultrasound scan is usually accurate to within about a week. But say you have a 28-day cycle, and you know the first day of your last period - all you have to do is work out 40 weeks from there. Now for most months of the year, that’s simply nine months plus one week. However this cycle of months does not include February - in other words if you get pregnant in March, April, or most of May then it’s not quite so accurate because February is a shorter month.

What pregnancy screening tests are available?

Dr Shazia Malik

When you are pregnant, your team of carers will offer you different stages of your pregnancy, tests that can check whether your baby is developing normally or whether there are any signs of abnormal pregnancy - for example, a baby with Down's syndrome. These tests occur at different stages of pregnancy. And I'll go through these in order. The first test occurs when you are about 12 weeks pregnant or so, and this involves a blood test and specialist ultrasound scan, which are then combined together to give you a risk or an idea of whether you are at high risk or low risk for having Down's syndrome or any other chromosomal abnormality.

The ultrasound and the blood test will also screen in for any physical abnormalities in your developing baby - for example, spina bifida - and this can also be picked up at this stage. All these tests are optional and you may choose to have or not to have some or all of these tests. Before you make a decision I would advise that you and your partner have a detailed discussion with your team so that you can take a best decision for you as a couple.

If the test does come back as high risk, the only way to know, for certain, will be further detailed test, such as an amniocentesis test, which will be offered to you by your team. Amniocentesis is where we put a needle inside the womb, take some fluid from around the baby and send the cells from the skin that are in the fluid to the lab to check the chromosomes; from that we can tell for certain whether your baby has Down's syndrome or another chromosomal abnormality. There is a small risk of miscarriage with this procedure. Between half to a one percent as one in a hundred of this procedure case are done. And all this will be discussed with you by your doctor before you decide whether you want to have the test or not.

Later in pregnancy you will be having an ultrasound scan at around 5 months or 19 or 20 weeks of pregnancy. This scan is to do a detailed assessment of the internal organs of your baby; by this time your baby is much bigger and your womb will be around the level of your tummy button. And so the person performing the ultrasound scan will have a detailed look into your baby’s heart, brain and internal organs inside the tummy. It’s a very important scan - abnormalities can be picked up at this stage. Further on in your pregnancy we may offer you another ultrasound scan if there is any concern that the pregnancy is not developing normally in terms of size and so we can do an ultrasound scan to check whether the placenta is working well and the size of your baby is what we would expect for you at your stage of pregnancy and whether the water is around the baby at a normal level and the placenta is not low lying. Of course at any other stage of pregnancy your team will offer you further tests as required.

What are the different stages of pregnancy?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

We tend to divide pregnancy into 3 month chunks or trimesters and there are three of them. In the first three months, most people around you won’t know you are pregnant but, by golly, you will. You often feel very very tired. You may feel very sick and you may some other symptoms such as breast tenderness and even to wee more often and so on. A lot of development is going on in your baby at that time. Even though by 3 months of age, your baby is only about the size of pea pod, you will be able to see the baby’s heart in ultrasound scan since about half way through that first trimester of pregnancy.

The second trimester of pregnancy from about 13 to 26 or 27 weeks of pregnancy is often a really a good time of pregnancy. The sickness is often gone. Your energy levels are often back to normal. In fact, you feel really blooming and the great thing is that the risk of miscarriage is dramatically dropped and your baby is often likely to start moving or you can feel your baby moving at between 17 and 18 weeks of pregnancy.

The third three month of period we call it last trimester, most of your baby’s development has happened already, it’s just the question of maturing the bits that are already there.But your baby is undoubtedly getting bigger and this is why you really start to notice yourself slowing down. You may find that the baby is pushing on your diaphragm so that you are getting more short of breath or pushing down below so you needing to wee every 5 minutes. You will often find it difficult to sleep. You may find your legs and ankles getting swollen and you are likely to find yourself getting much more tired. However, your baby is developing nicely, immune to all the discomfort you are going through and by nine months should be due to be born.

How does a baby develop in the womb?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

An extraordinary amount of development goes on in the first three months of your pregnancy. For about six weeks after your last period, you’ll already be able to see your baby’s heart on an ultrasound scan. By two months, your baby is about the size of a kidney bean and is got little limb buds or little webbed fingers that you can just about to see. By three months, their back bone is pretty much fully developed that's why is so important in first three months to take folic acid to reduce the risk of back bone problem, spina bifida.

By four months, their skeleton is really beginning to form very well that bones have started to be visible on the scan very properly. By six months, your baby is about one and half pounds in size. Their hair is continuing to grow. They beginning to fill up and lose that little skinny look and although they are not opening their eyes yet and they are not looking, those rods and cones at the back of their eye which would allow them to see, are starting to grow.

By seven months, they are opening and closing their eyelids and of course much of this is down to now maturing of those organs which have already developed. By eight months, really importantly, your baby’s lungs are about to develop and they need to be for them to survive and breathe in the outside world without problems and that's why if your baby is already over 36 weeks, we say they are, quote “full term,” and by nine months, well, you will very soon find out.

What are the early signs of pregnancy?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

The obvious first sign of pregnancy the most woman think of is missing a period but you can also get spotting around about the time baby would be implanting. If you get light bleeding with tummy pain, it could be an ectopic pregnancy or pregnancy outside the womb, so do be aware of that. Feeling sick and being sick are very very common, so is feeling really tired. It’s amazing how much change is going on your body.

Most of your baby’s organs, most of the hard work is actually happening in those first twelve weeks before anybody else knows that you are pregnant. Your breasts may feel swollen and tender. You may find that you need to wee more often and you often find that your taste changes. This could be connected with morning sickness. There are other things that could cause the same symptoms as pregnancy so the best way to be certain is not to rely on those symptoms but to do a pregnancy test.

How long does it take to get symptoms of pregnancy?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

When you miss the first day of your period it’s usually about four weeks since the first day of your last period and that's when your pregnancy will be counted from by your doctors and mid-wives. However, that’s actually only two weeks since your egg was fertilised by that sperm.

It’s around about four weeks from the first day of your last period that you tend to get a missed period and start to get early symptoms such as feeling tired, feeling sick, feeling need to wee more often and sometimes feeling breasts swelling and tenderness. A few women get symptoms before that, some women don’t get symptoms for a few weeks after that. But you are more likely to get symptoms early and more severe symptoms if you have a multiple pregnancy, in other words, twins or more.

Can you have pregnancy symptoms before your missed period?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

We count your weeks of pregnancy from the first day of your last period but in fact your egg meets that sperm which is going to fertilise it about two weeks after the first day of your last period. So, by the time you miss your first period, your sperm and egg have been together for just two weeks.

That’s quite early to be having symptoms, although, in some women even before they miss a period, can get symptoms like feeling sick or being sick, breast swelling, tenderness, needing to wee more and possibly feeling tired. Those symptoms are more likely if you hormones levels are very high and that particularly might happen if you got month old pregnancy.

What can cause the same symptoms of pregnancy?

Dr Sarah Jarvis, GP and Clinical Director of Patient.info

The early symptoms of pregnancy are often quite vague. Let’s think about them one by one. Missed periods, stress, excess exercise, all the years running up to the menopause can all cause your periods to become irregular or to stop happening. So too could be the condition of polycystic ovaries.

Feeling sick could just be due to a tummy bug. Feeling tired could be due to either a bug or to something like anaemia. There are lots of causes of tiredness. Coming up to the menopause, you may find that your periods become less regular and then stop completely. So, please don’t assume that it is the menopause before you’ve checked if you’re pregnant. And if your breasts are swollen and tender, well, that could be pregnancy. But it could be pre-menstrual fluid retention or possibly an infection in your breast.