Most pregnancies last between 37 and 42 weeks, and this period is referred to as "term pregnancy". It is common to be given a single 'estimated due date' EDD which corresponds to click at this page point at which it is estimated that your pregnancy will have lasted 40 weeks.
It may be more helpful to be prepared for your baby to arrive at some point after 37 weeks, and to focus on 42 weeks as the time by which you are likely to have given birth. This will be used to calculate your EDD, unless you decide to decline the scan. You may have your own information about when you became pregnant.
You may know that there were only specific dates dating which you could have conceived. If you conceived through IVF, you will know when your egg was fertilised.
One reason is that as soon as you reach your due date you are likely to be bombarded with enquiries about whether you have had your baby yet! In addition, the EDD will dating used by your midwives and doctors to try to work out whether your baby seems to be growing too fast or slow, or when to offer you an induction of labour to prevent a long pregnancy or for some medical reasonso it may be helpful to understand how firm a prediction it is.
There is sometimes a tendency for midwives and doctors to talk as though the EDD written in your maternity notes is something definite, rather than an estimate which may or may not be accurate. If the EDD you have been given is too early, this could mean that you are offered induction unnecessarily and potentially before your baby is fully prepared for life outside the share free sugar daddy dating apps consider. Alternatively, accuracy might be a dating reason such as pre-eclampsia which means it accuracy be better for your baby to be born as soon as they reach 37 weeks ultrasound pregnancy.
In that case, if the EDD is later than it should be that could mean that the birth is delayed inappropriately. Bringing forward the time of birth rather than waiting for labour to start may be the right decision for you, but it is always your decision whether to do this, and if so, at what point in your pregnancy.
For information about the situations in which you may be offered induction, and to help you decide accuracy whether and when to accept the offer you might like to have a look at our birth information page Induction of Labour or the "AIMS Guide to Induction of Labour'', which is available from the shop.
This suggests that in general ultrasound dating is more accurate in predicting the birth date than counting from the last menstrual period [3][4] but it is still only an estimate and may not always be accurate. A recent study [5] of women who conceived by IVF and therefore knew when their egg was fertilised, found that the routine ultrasound dating scan consistently put their estimated birth date earlier than it should have been by an average of 3 days.
In any case, ultrasound does not give an accurate prediction of the actual ultrasound not 7 ep marriage dating. The same study [2] showed that dating from ultrasound scans done later than 20 weeks is increasingly less accurate. If the date in dating notes has been changed because of a late scan, you might want to question how accurate that is likely to be, especially if it is being used to suggest the timing of an intervention.
If a ultrasound scan predicts a accuracy that is too early, this could make it appear that your pregnancy has lasted beyond 41 weeks the point at which induction is frequently offeredwhen in fact this is not the case.
Dating with ultrasound is a skilled procedure, so the accuracy of the EDD will also vary according to the experience of the person doing the measurement.
CLINICAL ACTIONS:
Oddly, even if you have good reason to know when you became pregnant you may find that your midwives and doctors put more faith in the ultrasound measurement if the two dates are different. If you believe that your estimate of your due date ultrasound more accurate, you may find it is quite hard to convince people of this. You may want ultrasound use your own knowledge about the length of accuracy pregnancy when making decisions, rather than the figure written in your notes, and perhaps record your own EDD in your notes.
We know that not all babies teethe or learn to walk at the same time, so why should all babies be ready accuracy be born after the same number of weeks in the womb? In fact, there dating plenty of evidence that there is variation in this, as in anything else to do with human beings. Other studies have suggested that the average length of pregnancy is 40 weeks plus days after the date of the last menstrual period, with birth tending to be a couple of days later, on average, this web page first babies than for subsequent ones [6][7].
Dating Scan
Recommendations about when to offer induction of labour to reduce a potential risk are based on data about how these risks appear to change through pregnancy across a whole population. It may therefore be helpful to consider whether there are reasons for you to expect a longer or shorter pregnancy than the average.
The length of pregnancy can be affected by many factors including genetics, ethnicity and length of the menstrual cycle. These are discussed below, but there may be other unknown factors which affect dating. It seems that some people are genetically programmed to have longer ultrasound average pregnancies, and some to have shorter ones.
Recent research has identified several genes which are associated with length of pregnancy and the likelihood of a pre-term birth [9] and so underpin this natural variation. The genetic heritage of both parents seems to affect the length of pregnancy. In a study [10] which looked at parents in Norway for whom birth data was available, fathers who were born at 42 weeks themselves had babies who were born, on average, 2 days later accuracy those of fathers born at 37 weeks. For mothers, the effect was even greater. Those born at 42 weeks birthed their babies, on average, 4 days later than those born at 37 weeks.
All of this means that a longer pregnancy may be normal for some people, and that their babies just need a bit longer than others to dating adelaide christian ready for the world outside.
Similarly, for others it may be normal to have a shorter pregnancy. As it is linked to dating heritage, it is to be expected that the typical length of pregnancy will also vary for people of different ethnicities, and there is some evidence that this is the case. For example, those of Black or Asian ethnicity appear to have slightly shorter pregnancies on average than those of white ethnicity [13].
In one interesting study [7] the researchers followed a group of mothers from before they became pregnant and measured their hormones daily. This meant that they knew exactly when each woman ovulated, when their egg was fertilised, and when the embryo implanted in the womb.
This showed that the date when a mother went ultrasound labour spontaneously was affected both by the length of time from the first day of her last menstrual period until she ovulated, and by how long it then took for the embryo to implant. If your menstrual cycle is longer than the average of 28 days, you are likely to have pregnancies that appear to ultrasound a bit longer than average and vice dating. The time it takes from fertilisation until the embryo implants also seems to vary a bit and that too could affect how long it is until your baby is ready to be born.
If you know when you ovulated or when you conceived, then counting from there may give a more accurate measurement than counting from the start of your last period. The 'due date' is only a rough estimate of when your baby is likely to be born.
It may be more helpful to think about the range of dates from 37 to dating weeks accuracy it is likely that you will give birth. Your family history, ethnicity and other personal factors can all affect how long your pregnancy will last.
A London-based study of overpregnancies with spontaneous onset of labour.
What is your due date?
AIMS does not accuracy medical advice. Our website provides evidence-based information to support informed decision-making. Please email helpline aims. We are a small charity that accepts no commercial sponsorship, in order to preserve our reputation for providing impartial, evidence-based information.
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Search, print or filter. How accurate is my 'due date'? What is a 'due date'? How is a 'due date' estimated? Why does the 'due date' matter? Is ultrasound dating accurate? How meaningful is a 'due date'? How might genetics affect the length of your pregnancy? How might your ethnicity affect the length of your pregnancy? How might your menstrual cycle affect the length of your pregnancy?
What else might affect the length of your pregnancy? Summary The 'due date' is only a rough estimate of when your baby is likely to be born.
I… Read more. The theme for this quarter explores different aspects of trust enc… Read more. Strengthening Midwifery Services: R… Midwifery in the UK has been facing severe and increasing challenges in recent years and trust in NHS midwifery services has been on the decline.
Can a new Labour governm… Read more. We acknowledge his ultrasound that maternity services are… Read more.