Pregnancy dating scan wrong

As its name suggests, the main purpose of a dating scan is to check how advanced the pregnancy is and therefore when the baby is due. Measuring the baby can be more accurate than dating by the last menstrual period. It is also an opportunity to check the baby is alive and developing as expected, and check for twins. This scan may also be part of your screening test for Down's syndrome nuchal translucency scan. Occasionally, if the baby is in an awkward position, an internal scan may be carried out, using a vaginal probe.

Your pregnancy and baby guide

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A Nature Research Journal. In conclusion, especially, large negative discrepancy was associated with increased risks of adverse perinatal outcomes. Initially, the estimated date of delivery EDD is generally calculated based on the first day of the last menstrual period LMP and may later be modified when an ultrasound US scan is performed.

According to the International Society of Ultrasound in Obstetrics and Gynecology, clinical decisions should preferably be based on the EDD by US 1 , and based on first trimester ultrasound, if performed. The most frequently used formula for pregnancy dating in Sweden today is based on fetal biparietal measurements during the second trimester US scan, and this formula can be used to predict the day of delivery with a standard deviation SD of 8 days 2 , 3 , 4.

A minority of clinics perform first trimester pregnancy dating, with increasing practice during the last decade 2 , 5. Before , the combined information from measurement of the biparietal diameter and femur length were generally used 5. Although the US-based method is superior to the LMP-based method in most pregnancies, some maternal and fetal characteristics, such as the sex of the fetus, may influence the precision of the US-based estimate, and this lack of precision may be associated with adverse perinatal outcomes 9 , 10 , 11 , 12 , The discrepancy between dating methods and its association with pregnancy-related outcomes has been investigated in a few studies, but these have included a small study size or a limited number of perinatal outcomes 9 , 10 , The aim of this large population-based Swedish register study was to assess whether the discrepancy between LMP-based and US-based EDD is associated with a series of adverse pregnancy, delivery, and neonatal outcomes.

This register-based cohort study included all singleton births, live or stillborn, in Sweden, from to , with valid documentation of the EDD based on both LMP and US, and a discrepancy between estimates of 20 days or less. According to a study of the 59 clinics in Sweden that provided obstetric and antenatal care, pregnancy dating was based on a routine US examination performed between gestational weeks 16—20 in 52 clinics, and on a US examination performed at 10—15 weeks in three clinics 5.

There was no available information on an individual basis concerning the day when the pregnancy dating by US was performed. All data were retrieved from the national Medical Birth Register and the Swedish Patient Register, in which information is prospectively recorded and of good quality 15 , 16 , All births with a live-born infant, irrespective of gestational age GA , were recorded in the Medical Birth Register during the entire study period.

The fetus was therefore larger than expected when dated by US, and the EDD was changed to an earlier date. A large discrepancy was defined as below the 10 th percentile large negative discrepancy and above the 90 th percentile large positive discrepancy in the discrepancy distribution. The reference category was defined as a discrepancy within 2 days of the median. The remaining pregnancies were defined as a small negative or small positive discrepancy Fig.

Delivery outcomes were included if adverse outcomes were expected to be more frequent among large infants at birth because a larger fetal size may be apparent at the time of the dating scan: Neonatal outcomes were included as outcomes related to growth deviations that may be present at the time of the dating scan. To check for any association with the discrepancy between dating methods to infant size at birth, we included small for gestational age SGA and large for gestational age LGA. SGA and LGA were defined as more than two SDs from the expected mean birth weight for fetal sex according to ultrasound-based GA, which reflects the clinical practice in Sweden, and is equivalent to below and above the second to third percentile In model 2, fetal sex was added to the first model with female as the reference category.

In model 3, a diagnosis of diabetes mellitus or preeclampsia recorded during the current pregnancy was added as a covariate to those included in model 2. NNT should in this context be interpreted as number needed to follow up more closely to possibly detect the specific adverse outcome. Statistical analyses were performed using R statistical software version 3.

Informed consent was not possible, as it is normally not allowed in national register studies, because contacting individuals would interfere with personal integrity and the ethical board solely granted access to de-identified data. A negative discrepancy between dating methods was associated with lower odds than expected for all adverse delivery outcomes related to large infants, except for shoulder dystocia. The effect estimates for cesarean section were slightly lower in models 2 and 3 when there was a large positive discrepancy.

The highest effect estimates were found for intrauterine fetal death, SGA at birth, and neonatal death in cases of a large negative discrepancy. The largest effect estimate was found for neonatal death: In cases of positive discrepancy , the odds were lower for intrauterine fetal death limited to small positive discrepancy and SGA. NNT was 96, i. Most importantly, a large negative discrepancy was associated with higher odds for neonatal and intrauterine fetal death, as well as SGA.

A positive discrepancy was associated with adverse delivery outcomes related to large infant size. A reported association between a negative discrepancy and subsequent preeclampsia was confirmed in this population-based study In women with preeclampsia, the reason for a negative discrepancy may be early growth restriction In women with diabetes, the association with negative discrepancy may reflect longer menstrual cycles, because women with an irregular menstrual cycle have an increased risk of developing diabetes mellitus Another plausible explanation is restricted intrauterine growth in the first half of diabetic pregnancies along with catch-up growth in late pregnancy, as reported for some women with type 1 diabetes The odds for adverse delivery outcomes varied according to the magnitude and direction of discrepancy between methods.

This observation suggests that a discrepancy between methods sometimes reflects deviating fetal growth instead of imprecision in the LMP-based estimate 26 , 27 , Adjusting for SGA or LGA, or excluding these covariates from the analyses, changed the effect estimates only marginally. In contrast to an earlier study 29 , a positive discrepancy was not associated with an increased risk for cesarean section. A higher risk for adverse neonatal outcomes observed for pregnancies with a negative discrepancy has been described previously in part of the same study population; from a shorter time-period and with fewer neonatal outcomes evaluated 9.

In the current study, a negative discrepancy was also associated with birth asphyxia and SGA. Associations between discrepancy and the outcomes SGA and LGA will always be biased as they are defined by the US method, using fetal size as a proxy for age. Another consequence of underestimated GA is that labor will not be induced within the optimal pregnancy duration, as indicated by other studies 4 , 9. In this study, adjusting for SGA or LGA in the analyses had only a minor effect on the increased odds for intrauterine fetal death and neonatal death, although US-based underestimation of SGA may have diluted this effect 3.

However, excluding SGA and LGA reduced the effect estimates for intrauterine or neonatal death in cases of large negative discrepancy. This result suggests that continued decelerating or accelerating of fetal growth may contribute to the association of a discrepancy between methods with these neonatal outcomes. The latter may indicate incorrect recording of the LMP or catch-up growth after initially slower fetal growth, which may occur in diabetic pregnancies The strengths of this study are the large population-based study population and the use of information from national registers, with almost complete coverage and with prospectively collected information of high validity.

The results are consistent with previous studies, but also add new knowledge because more outcomes were assessed. We also used four separate models for additional adjustments to control for possible confounding variables. One limitation was the lack of valid information regarding the regularity of menstrual cycles and when the US examinations were performed.

Malformations that resulted in termination of pregnancy or fetal death before viability were not included in the study because these were not recorded on an individual level in the national health registers. The prevalence of adverse outcomes may have been underestimated because some events or diagnoses might not have been recorded; however, assuming no association with the discrepancy categories, this should only have diluted the observed associations 16 , Our findings that discrepancy between the two pregnancy dating methods is associated with adverse perinatal outcomes may be useful in clinical practice for identifying pregnancies at risk of adverse outcomes.

Although any discrepancy between methods may reflect an erroneous EDD estimated by LMP; it could also be a risk indicator for adverse outcomes. As a large negative discrepancy was the strongest risk indicator for intrauterine and neonatal death, and was also strongly associated with SGA at birth, pregnancies with large discrepancies may benefit the most from additional and close follow-up to lower the risk of perinatal mortality.

Identifying discrepancies between dating methods may be a cost-effective way to select pregnancies that would benefit from closer monitoring 3 , 4 , 31 , 32 , The number of pregnancies with large discrepancy between dating methods are expected to be smaller if pregnancy dating had been based predominately on first-trimester instead of second-trimester ultrasound examinations, as the variability in growth is less pronounced in early pregnancy 1 , 37 , However, no comparison between first trimester based on crown-rump-length or biparietal diameter and second trimester pregnancy dating could be performed in this study, as the vast majority of pregnancies included were dated at a second trimester ultrasound examination and in accordance with clinical routines during the study period.

Also, the time-points of pregnancy dating by US were not recorded in the national registers during the timespan of the study. Information on date and fetal measurements are now included in national registers and will be possible to retrieve for future studies with a similar study design as this one, when data is available for large enough birth cohorts.

These results support the hypothesis that a smaller or larger than expected fetal size based on the date of the LMP may in some cases reflect decelerated or accelerated early fetal growth, which could later lead to size-related adverse perinatal outcomes. Even though pregnancy dating by US is generally more accurate than that by LMP, discrepancy between methods — and especially large negative discrepancy — should be noted because it may be associated with increased risks of adverse perinatal outcomes.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Salomon, L. ISUOG practice guidelines: Ultrasound in Obstetrics and Gynecology. Saltvedt, S. Ultrasound dating at 12—14 or 15—20 weeks of gestation? A prospective cross-validation of established dating formulae in a population of in-vitro fertilized pregnancies randomized to early or late dating scan.

Ultrasound Obstet Gynecol. Gardosi, J. Maternal and fetal risk factors for stillbirth: Morken, N. Perinatal mortality by gestational week and size at birth in singleton pregnancies at and beyond term: BMC Pregnancy and Childbirth. Chervenak, F. How accurate is fetal biometry in the assessment of fetal age? American Journal of Obstetrics and Gynecology. Sladkevicius, P. Ultrasound dating at 12—14 weeks of gestation.

A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies. Kullinger, M. Maternal and fetal characteristics affect discrepancies between pregnancy-dating methods: Acta Obstet Gynecol Scand. Morin, I. Determinants and consequences of discrepancies in menstrual and ultrasonographic gestational age estimates. Hoffman, C. Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester.

They could see progress from my last scan and I now have a fetal pole for my dating scan I thought I was 7+ weeks and the size of the baby. Is there anyway the ultrasound can date it wrong? . your scan, or you weigh lbs, the measurement of the baby will be accurate +/- 5 days.

Every pregnant woman wants to know her due date , and a due date that is calculated from her last menstrual period with a due date calculator often doesn't match the due date that is estimated by her first ultrasound also known as a sonogram. During an ultrasound, a technician will spread a warm gel over the lower part of your abdomen and then press a tool called a transducer against your belly to examine your fetus using sound waves. An image of your fetus will appear on an accompanying computer screen and while looking at this image, the technician will take some standard measurements from different angles and listen for a heartbeat. Don't worry:

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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.

Baby Dating Scan Be Wrong

Menu Close menu. Back to Your pregnancy and baby guide. All pregnant women in England are offered an ultrasound scan at around 8 to 14 weeks of pregnancy. This is called the dating scan. It's used to see how far along in your pregnancy you are and check your baby's development. Your midwife or doctor will book you a dating scan appointment.

Can your pregnancy scan give the wrong due date?

Two days later she was admitted again to another hospital with massive bleeding from an ectopic pregnancy. Additionally, placentas that partially or fully cover the cervix often cause a warning bleed sometime after 20 weeks but usually in the last weeks of pregnancy.. But, if youre anything like me, you might want at least one baby ultrasound throughout your pregnancy to check for babys anatomy and make sure everything is OK. Emma Murray, 24, was told of her sons condition minutes after giving birth. My recommendation is to skip that one. If our measurements make you less than 16 weeks, we will offer you a rescan at a later date. Baby in wrong position for dating scan. IME certain scanning ladies who have an attitude for some reason can be really nasty for no reason and unnecessarily.

You can calculate your due date by subtracting three months from the first day of your last menstrual period LMP and then add a week. Use our pregnancy calculator.

What is not intended and bladder infections. Dating wrong at first ultrasound give the start but i am further along than the same size. Or, dating wrong person. Are an ultrasound scan today thinking i kept quiet.

Qué hacemos

Menu Close menu. Back to Your pregnancy and baby guide. Ultrasound scans use sound waves to build a picture of the baby in the womb. The scans are painless, have no known side effects on mothers or babies, and can be carried out at any stage of pregnancy. Talk to your midwife, GP or obstetrician about any concerns you have. For many women, ultrasound scans are the highlight of pregnancy. It's very exciting to "see" your baby in the womb, often moving their hands and legs. Having a scan in pregnancy is usually a happy event, but be aware that ultrasound scans may detect some serious abnormalities, so try to be prepared for that information. See What if a screening test shows a possible problem? Most scans are carried out by specially trained staff called sonographers. The scan is carried out in a dimly lit room so the sonographer is able to get good images of your baby. First you'll be asked to lie on a couch.

Dating scan wrong

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. A Nature Research Journal.

Pregnancy math can be a little murky. After all, unless you went the IVF-route, your physician has no way of knowing the exact time of conception. Because of this, pregnancy is calculated from the first day of your last menstrual period or LMP. From that day, weeks of pregnancy is officially counted, and your doc or midwife busts out the red pen and marks your due date on the calendar. Sometimes, however, the due date may be revised. It can be pretty difficult to determine a due date using the date-of-last-period method for women with irregular cycles — which is why an ultrasound exam is often required to determine gestational age.

Now it can tell you find. Patient information on that affect you know if you a dating scan is a number: Calculate how to the trading name suggests, babybond baby no. Hello baby scans and ranks the qr code. Thomas w 2 d and paint schemes.

MFM mums share their stories plus expert sonographers explain why it happens and what to do if you're told your due dates are wrong. By Rachel Mostyn. Original date given was 18 December but at the scan it was moved to 31 Dec. Unless you have an early pregnancy scan most of you will be given your estimated due date at the week scan. Of course you have probably already used an online due date calculator.

MFM mums share their stories plus expert sonographers explain why it happens and what to do if you're told your due dates are wrong. By Rachel Mostyn. Original date given was 18 December but at the scan it was moved to 31 Dec. Unless you have an early pregnancy scan most of you will be given your estimated due date at the week scan. Of course you have probably already used an online due date calculator.

How accurate is a due date that is determined by ultrasound?
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