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Are Ultrasounds Accurate for Predicting Due Dates?
4 May The aim of the present study was to determine the accuracy of different dating formulae in estimating gestational age when dating was performed at 12–14 and 15–20 weeks. For this purpose, 10 published dating formulae based on BPD or BPD/FL were applied to a population of singleton pregnancies. The earlier the ultrasound is done, the more accurate it is at estimating the baby's due date. 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. 27 Oct Evidence suggests that, in the first 20 weeks of pregnancy, the first ultrasound may be the most accurate tool for predicting when your baby will be born. But early ultrasound due dates have a margin of error of roughly weeks, so doctors will usually keep the original due date (the one generated by the.
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For more information, please visit our migration page: Previous article in issue: Nomograms of sonographic measurements throughout gestation of the fetal hard palate width, length and area. Next article in issue: Antenatal renal sonographic anomalies and postnatal follow-up of renal involvement in Bardet—Biedl syndrome. To determine the accuracy of established ultrasound dating formulae when used at 12—14 and 15—20 gestational weeks. A total of singleton pregnancies conceived after in-vitro fertilization IVF and randomized to a dating scan at 12—14 or 15—20 gestational weeks were studied.
The mean of the more info between estimated and true gestational age systematic measurement error and their SD random measurement error were calculated for each formula.
Two formulae overestimated gestational age at both early and late scanning by 5. The formulae used for clinical management underestimated gestational age by a mean of 3 days when dating was performed at 12—14 weeks, and by a mean of 0. The random error was on average 1 day less when the scan was carried out early 2 vs.
Mean true gestational age at delivery in IVF pregnancies with spontaneous start of labor was days SD Ultrasound dating formulae originally intended for use in the middle of the second trimester do not necessarily perform well when used for dating earlier in gestation. The systematic and random error of any dating formula must be assessed for the gestational age interval in which the formula is intended to be used. Determination of gestational age by ultrasound is a routine clinical procedure in many countries and is usually performed at 15—20 gestational weeks.
However, during the past decade the use of serum screening and fetal nuchal translucency NT screening for Down syndrome 1—3 has resulted in more pregnancies being examined and dated at 11—14 weeks. Reliable information about gestational age is necessary to diagnose fetal growth restriction and is essential for optimal management of pre- and post-term pregnancies. Ultrasound dating in the second trimester is more accurate than the last menstrual period LMP for predicting delivery date 4—7. Many commonly used mathematical models using measurements of the fetal biparietal diameter BPD and the fetal femur length FL were designed to calculate gestational age from 14 gestational weeks 89.
Generate a file for use with external citation management software. By continuing to browse this site you agree to us using cookies as described in About Cookies. You need to be logged in to do this Prenat Diagn ; According to ultrasound dating using the two dating formulae with the best performance Selbing and Kjessler 18Mul et al.
Dating formulae and charts based on BPD measurements in earlier gestation have been designed, some of them being based on transvaginal measurements 1011 and others on transabdominal measurements 4 To the best of our knowledge, no other research team has prospectively validated any first- or second-trimester formula with regard to their accuracy in estimating gestational age when dating is performed in the interval between 12 and 14 weeks.
In Sweden, a randomized controlled trial, the NUPP Study, was undertaken to compare the medical, psychological and economical effects of a routine fetal scan at 12—14 weeks with those of a scan at 15—20 weeks. The aim of the present study was to determine the accuracy of different dating formulae in estimating gestational age Accuracy Of Ultrasound Dating At 20 Weeks dating was performed at 12—14 and 15—20 weeks.
In addition, we analyzed the effects of using those formulae that had the best performance in our IVF pregnancies in a larger population comprising spontaneously conceived pregnancies. The trial was approved by the ethics committees at the Karolinska Institute in Stockholm and at the medical faculties of Lund University and Uppsala University. It enrolled 40 pregnant women who were randomly allocated to ultrasound examination at 12—14 or 15—20 gestational weeks.
Randomization started in March and finished in October Randomization was performed using a computerized Internet-based program developed by Medscinet AB, Sweden more info which also demographic data, data from ultrasound examinations and invasive tests and information on pregnancy outcome were continuously registered.
Find Out How Well a Sonogram Can Tell You Your Due Date
Inclusion criteria were BPD 21—31 mm at the 12—week scan, BPD 32—60 mm at the 15—week scan and a liveborn baby with no fetal malformations or chromosomal anomalies. After exclusions our IVF population comprised women, randomized to a dating scan at 12—14 weeks and to a dating scan at 15—20 weeks Figure 1. The early and late scan groups were similar with regard to age mean age Characteristics of pregnancies conceived after in-vitro fertilization including details of exclusions.
In a second stage we analyzed the effects of using the formulae with the best performance in our IVF population for dating in a larger population of pregnancies conceived spontaneously. This population comprised women included in the NUPP Study between September and May fulfilling the following inclusion criteria: Of these women, were examined at 12—14 weeks and at 15—20 weeks. Mean age was The dating scans were scheduled to take place at 12—14 weeks early scan group or at 15—20 weeks late scan group according to the day of oocyte retrieval in IVF pregnancies and according to the LMP in spontaneously conceived pregnancies.
The examinations were source by specially trained midwives with 1—25 mean, 11 years' experience of routine ultrasound examinations at 15—22 weeks.
Before the study started all the midwives had received a certificate of competence in the theory and practice of the 11—week scan from The Fetal Medicine Foundation, London, UK. All examinations were performed transabdominally using any Accuracy Of Ultrasound Dating At 20 Weeks the following ultrasound systems: Fetal anatomy was examined in both groups. The BPD was measured from Accuracy Of Ultrasound Dating At 20 Weeks outer to the inner edge of the parietal bone in a transverse plane which aligns the cavum septi pellucidi and third ventricle with the thalami 13 The near field femur was measured in a straight line from one end of the diaphysis to the other 15 At the early scan FL was not always measured.
For all parameters the mean of three replicate measurements was used. In this paper, gestational age was used synonymously with menstrual age. Gestational age according to oocyte retrieval was regarded as the true gestational age.
The hash symbol denotes the formula number where a reference contains multiple formulae. BPD, biparietal diameter; FL, femur length. When testing the formulae in the larger pregnant population, the estimated day of delivery was at completed gestational days. Measurement error was defined as the difference in days between the gestational age at the dating scan calculated on the basis of ultrasound fetometry and the true gestational age according to oocyte retrieval.
The mean measurement error was compared between the early and late scan group using Student's two-sample t -test and an F -test. A t click against zero was used to analyze if the mean measurement error was statistically significant. The mean of the measurement errors reflects the systematic measurement error i.
The statistical significance of differences in proportions was determined using the Chi-square test or McNemar's test, where appropriate.
The statistical significance of differences in gestational age at delivery was calculated using Student's two-sample test. The distribution of BPD at examination is shown in Figure 2. The measurement errors for the formulae tested and the statistical significance click differences in measurement error between the early and the late dating group are shown in Table 2.
Two formulae resulted in substantial overestimation of gestational age in both groups Hadlock et al. For six formulae, including one of the formulae that overestimated gestational age in both groups, the measurement error differed significantly between the 12—14 weeks and the 15—20 weeks groups, the measurement error being significantly larger in the early scan group for five of the six formulae. The formulae used for clinical management underestimated gestational age by a mean of 3 days when dating was carried out at 12—14 weeks and by a mean slightly less than 1 day when dating was performed at 15—20 weeks.
The SD of the measurement error was approximately 2 days in the early scan group and 3 days in the late scan group. This formula was used clinically at dating scans at 15—20 weeks. Pregnancy duration in the IVF pregnancies is Accuracy Of Ultrasound Dating At 20 Weeks in Table 3 and pre- and post-term rates in Table 4.
There was no difference in mean pregnancy duration at delivery between the early and the late scan group irrespective of whether gestational age was calculated on the basis of oocyte retrieval or on the basis of the dating formulae with the best performance Mul et al. Among the women with IVF pregnancy and spontaneous start of labor, 14 5.
According to ultrasound dating using the two dating formulae with the best performance Selbing and Kjessler 18Mul et al. A comparative analysis of second-trimester ultrasound dating formulas in pregnancies conceived with artificial reproductive techniques. Two formulae were associated with a substantial overestimation of gestational age Hadlock et al.
According to ultrasound dating using the article source dating formulae with the best performance Selbing and Kjessler 18Mul et al.
When we applied the BPD formula that we used clinically Persson and Weldner 1 8 to the 12—14 weeks scan group the post-term rate was much lower 0. Table 5 shows pregnancy duration according to ultrasound fetometry in spontaneously conceived pregnancies.
Using two dating formulae that showed very small systematic and random errors Selbing and Kjessler 17Mul et al.
Our results show that dating formulae originally designed to estimate gestational age in the middle of the second trimester are not necessarily applicable earlier in gestation.
Other BPD formulae were good either at early or at late dating but not at both Persson and Weldner 1 8Hadlock et al.
Ultrasound Examination | Establishing the Gestational Age of the Pregnancy | Ultrasound Care
Both formulae of Persson and Weldner, which are widely used for second-trimester dating in Scandinavia, performed well when dating was carried out at 15—20 please click for source, but substantially underestimated gestational age when dating was performed at 12—14 weeks. An ideal dating procedure is associated with no systematic error and a small random error. To achieve this we need a formula that performs well throughout our dating interval.
Moreover, the ultrasound examiners must take precise measurements, and the technique must be the same as that used when the formula was designed. In the present study the systematic error of some formulae was very similar in the early and late scan groups, whereas that of other formulae differed substantially between the two groups. This suggests that the differences in systematic error between the early and late scan groups are explained by differences in performance between formulae and not by differences in measurement technique.
Random error can be explained by biological variations in fetal size and by the precision of the measurements. In the present study the random error was very similar for all formulae tested. It was on average 1 day smaller at early dating than at late dating.
Smaller random errors at early dating scans than at late dating scans were also found by others 12 It probably reflects smaller biological variation in fetal size at earlier gestation, even though a difference in measurement technique between early and late scans cannot be excluded.
One of the best formulae in our study was that of Selbing and Kjessler. Their formula was designed on the basis of measurements of BPD taken at 9—22 weeks in women in whom gestational age according to the LMP had been confirmed by a CRL measurement Mul and colleagues designed dating formulae that were based on measurements taken at 14—24 weeks in 64 IVF pregnancies Despite the formulae of Mul and coworkers being designed on the basis of measurements taken later in gestation and in only 64 pregnancies, we confirmed the accuracy of their formulae both in our early and late dating group.
The formulae by Persson and Weldner were designed on the basis of 67 measurements taken longitudinally between 11 and 24 weeks in 14 women with reliable ovulation date according to basal body temperature charts. Mul and coworkers tested several established dating formulae in their 64 IVF pregnancies Performing the scans at 14—24 weeks, they found an overestimation of gestational age by 1 day for the BPD formula of Selbing and Kjessler, an underestimation by 0.
These figures are in accordance with the results in our late dating group, with the exception that the Accuracy Of Ultrasound Dating At 20 Weeks of Selbing and Kjessler performed better in our hands.
Possibly, the Accuracy Of Ultrasound Dating At 20 Weeks is to be explained by a difference in gestational age at dating. Mul and coworkers performed their dating at 14—24 weeks, whereas almost all women in our late group were scanned before 20 weeks.
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Our results in the late dating group are also in accordance with those of Chervenak and coworkers, who tested 38 previously published dating formulae, including seven of the formulae tested in our study, in singleton IVF pregnancies They calculated true gestational age from the day after oocyte retrieval.
In both studies cited 2021the dating scans were carried out in the second trimester. Thus, both in our study and in those of Geirsson and Have and Wennerholm and coworkers, the formulae of Persson and Weldner underestimated gestational age when dating was performed in the second trimester.