Can a baby's due date be a month off when determined by an ultrasound?
Are Ultrasounds Accurate for Predicting Due Dates?
3 Nov An ultrasound exam is a procedure that uses high-frequency sound waves to scan a woman's abdomen and pelvic cavity, creating a picture (sonogram) of the baby and placenta. Although the terms ultrasound and sonogram are technically different, they are used interchangeably and reference the same. OBJECTIVES: To determine the accuracy of established ultrasound dating formulae when used at and gestational weeks. METHODS: A total of singleton pregnancies conceived after in-vitro fertilization (IVF) and randomized to a dating scan at or gestational weeks were studied. Had a pregnancy ultrasound that doesn't match your Estimated Due Date (EDD)? MFM mums share their stories plus expert sonographers explain why it happens and But Nigel also says that the estimated (and that is all it is) date is normally accurate plus or minus about a week. I've not even had my 20 week scan yet.
A dating scan is an ultrasound examination which is performed in order to establish the gestational age of the pregnancy. Most dating scans are done with a trans-abdominal transducer and a fullish bladder.
If the pregnancy is very early the gestation sac and fetus will not be big enough to see, so the transvaginal approach will give better pictures. Dating scans are usually recommended if there is doubt about the validity of the last menstrual period. By 6 to 7 weeks gestation the fetus is clearly seen on trans-vaginal ultrasound and the heart beat can be seen at this early stage 90 to beats per minute under 6 to 7 weeks, then to beats per minute as the baby matures.
Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation. This is because the fetus is growing so quickly that there is a big difference in size from week to week.
Babies are ready when they're ready - try not to worry easier said than done. I know I will be very pissed if I get to the end and find that source is overcooked. How to cite this comment: No as acurate but neither is going off the date of your LMP With it so far out they will probably go off the new date.
However, the accuracy of the ultrasound examination is always dependent on the skill of the sonographer and the quality of the equipment. The EDD from the early dating scan is used - if the last menstrual period is not known or is unreliable, or the dating scan differs from the last menstrual period dating by more than 5 days.
Ultrasound examinations from 12 to 22 weeks are regarded as being within 10 days of accuracy or up to 10 days earlier or 10 days later than the woman's calculated due date. Ultrasounds performed after 22 weeks gestation cannot be used to estimate the due date of the baby because the size no longer reflects the age very well. Even average babies can differ by up to 2 to 3 "weeks of growth".
Three formulae showed systematic errors of less than If you know the date of your LMP and length of cycle then that will give you an accurate date. At the 20 weeks scan she measured 17 weeks and they made me go back in 2 weeks when she measured 19 weeks.
These scans are only used to estimate the due date of your baby if this is all you have to go on. If you have more than one ultrasound during your pregnancy, giving you 'multiple dates', then the earliest ultrasound estimate should be used, because it will be more accurate.
If you have any questions about this, please feel free to talk to your sonographer or doctor about it. Find Us Make An Appointment. No one logged in.
Can your pregnancy scan give the wrong due date?
Dating and viability What is a dating scan? Dating scans also reveal other important information such as: For transvaginal ultrasound you can have an empty bladder When is it recommended? For example if you do not know when the first day of your last period, or the likely day of conception was have had irregular periods have had an unusual cycle because you recently stopped the oral contraceptive pill, or you recently had a miscarriage, or you are breast-feeding had some implantation bleeding which can be been confused with your last period date What can be seen?
Gender Reveal Ultrasound! WRONG!
This is presuming that the pregnancy is actually at this stage of development. Sometimes a trans-vaginal examination shows that your pregnancy is less advanced than expected. How accurate is the ultrasound examination? The earlier the ultrasound is done, the more accurate it is at estimating the baby's due date. Also the fetus cannot bend and twist too much yet, so the click of the body is fairly constant.
The scan or my dates - which should I believe? As the baby gets bigger, it starts to express its individual growth potential. The size of the baby correlates less and less with its age as time goes on. You can estimate the due date of the baby by using our pregnancy calculator.
What can be seen?
Are late scans accurate for dating? in Your Pregnancy | Forum | Huggies