First Trimester

Finding Your Due Date

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Working out the baby's due date is often one of the first things that women do when they discover that they are pregnant. However, it is only a very small percentage of babies (approximately 5%), that are actually born on their due date. Regardless of this, the due date remains of great significance throughout the term of the pregnancy and beyond for a number of reasons.

How your due date is calculated

Your estimated due date is calculated from the first day of your last period. Your estimated due date will be 40 weeks after this date. This is based on a 28 day menstrual cycle, so if your cycle is shorter or longer, then the due date will need to be adjusted to take account of this. There are a number of online calculators available that can work out your estimated due date.

This method of calculating your due date can be confusing, as at the time you conceive you are already classed as being 2 weeks pregnant! This is because the starting point for the calculation is the date of your last menstrual cycle, rather than the date of conception.

Use our due date calculator to calculate your due date.

Dating scan

As part of your antenatal care, you will be offered a scan between 10 and 14 weeks of your pregnancy. At the scan, a sonographer will rub some gel on your tummy and move a device over this gel. As well as getting your first view of your baby, the sonographer will check your baby's heartbeat and measure the baby's length to accurately date your pregnancy. Your due date may be revised at this stage based upon the findings at the scan. You will also be offered a screening at this scan to check for any abnormalities.

Why is a due date important?

There are a number of reasons why it is important to accurately forecast the due date of your pregnancy. Some are to give the mother peace of mind; some to ensure the baby's well-being and others are financial reasons why you may need to know when you are due.

Monitoring the baby

One of the reasons that it is important to accurately calculate your due date is so that the development of your baby can be monitored. If your baby is small or big for its dates, it is not necessarily due to a problem, although it is something that the health professionals involved in your care will want to investigate.

Helping mum prepare

Being pregnant for the first time can be overwhelming. One of the benefits of knowing when your baby is due is that you can plan towards it. By knowing the due date, it is possible to understand what is happening to your body at various points during the pregnancy, as well as knowing what stage of development the baby is at and whether anything you are experiencing is a cause for concern. It also serves as a deadline for making sure you have, at the very least, nappies, clothes and sleeping arrangements organised for your new arrival!

Premature baby

Your due date is important in establishing whether your baby will be premature and will need special care. A baby born before 37 weeks is termed premature and extra attention is needed both during labour and after the birth. Babies born prematurely often spend time in the hospital's special care unit as a precautionary measure, even if they appear perfectly healthy.

Overdue baby

Your due date will also have an impact if your baby becomes overdue. If you are only a few days late, then it is not seen as a cause for concern. If you reach 41 weeks and there is still no sign of the baby, then your midwife may offer you a membrane sweep to try and trigger labour. If this is unsuccessful, then you may be offered an induction to start labour. This is because the placenta starts to deteriorate after you reach full term and its ability to support your baby can be compromised.

Statutory maternity pay

If you are in employment, your due date also has an impact on your ability to claim statutory maternity pay from your employer. One of the conditions that you have to meet to claim this benefit is continuous employment with your employer for 26 weeks into the 15th week before your baby's due date. If you do not qualify for statutory maternity pay but have been working, you may be able to claim maternity allowance.

Your baby's due date is important throughout your pregnancy from the initial estimate to the more accurate dating scan, through to the birth itself. It is one of the key pieces of information that allows everyone involved in this important journey to prepare and respond as is appropriate. It is always worth remembering, however, that very few women actually give birth on their due date so be prepared well in advance of this date!

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This internet site provides information of a general nature and is designed for educational purposes only. If you have any concerns about your own health or the health of your child, you should always consult a doctor or other healthcare professional.