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Crown rump length dating calculator

The DLA and the DoDx provided the lower and upper limits for the timing of death interval for each stillborn fetus. Individual cases were then reviewed by the SCRN clinical site investigator if the estimated gestational age at the DoDx differed by more than 2 weeks from the clinical GA recorded by the site. When this review identified transcription errors in medical charting or chart abstraction, the database was corrected and the algorithm re-applied.

For discrepancies that remained, the EDD could be set by the clinical site investigator, overriding the EDD by algorithm if deemed valid based on clinical documentation. EDDs re-assigned by case review were considered reliable for the purpose of estimating GA at death. The algorithm estimated the GA at fetal death and the date of death by incorporating several factors: These cases were considered to have the most precise information regarding the date of death, the estimate of which we took as the date of diagnosis identified by the algorithm. Instead, GA at death was estimated using foot length row B , or using clinical GA when foot length information was not available row C.

Arrows show the direction of the computation of either the GA at Death estimate or the Date of Death estimate; where no arrow is shown, the two estimates were derived separately. Percentages are based on the singleton stillbirths. See Appendix B for formulas for calculating the estimates. For the remaining women, estimation of GA at fetal death proceeded in a hierarchical fashion depending on the length of the timing of death interval and which clinical dating criteria applied.

When the EDD was reliable and foot length available row G , GA by foot length was used as the GA at death if it fell within the GA range associated with the timing of death interval; if it did not, the gestational age at the end of the timing of death interval closest to GA by foot length was used.

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If the EDD was reliable but the foot length was not available row H , the date of diagnosis was taken as the most reasonable estimate of the date of death, and the reliable EDD was used to calculate the GA at date of diagnosis as the estimated GA at death. We identified a well-dated subset of the stillbirth cases with both clinically reliable gestational dating criteria and a short timing of death interval, and who had a foot length measurement recorded.

These cases met the following criteria: By the rules of the algorithm, GA by foot length was not needed to estimate GA at death in this subset. Thus, the GA at death estimated by the algorithm was compared to the GA by foot length in order to assess the validity of using foot length alone in the algorithm to estimate GA at death figure 2 , rows B, E, I.

Summary statistics were used to describe the results. Statistical significance for comparisons of proportions between independent groups e. The SCRN identified eligible women with stillbirths for participation in the study. These singleton pregnancies are the subject of this analysis. Of these, 27 4. In 41 cases 6. Ultrasound results were used to revise the EDD in 54 cases 8.

Including the 41 cases in which there was no documentation of a living fetus at any point, there was no objective documentation that the fetus was alive within four weeks before the stillbirth diagnosis in About one fourth Numbers at the base of each bar show the percentages represented by bar height. Figure 2 shows the number of cases for each method used to estimate the GA at death. The frequency and cumulative frequency distributions of the algorithm-assigned GA at death and the clinical GA for these singleton stillbirths are shown in Figure 4.

The cumulative distributions indicate that the percentiles of the estimated GA are smaller than those of the clinical GA estimate up to 38 weeks gestation. The left axis shows the number of stillbirths with each gestational age for the frequency curves. The right axis shows the total number of stillbirths with gestational age at a given week or earlier for the cumulative distribution curves.

The final algorithm-assigned GA at fetal death was 1 or more weeks less than the gestational age at the algorithm-derived date of diagnosis of fetal death DoDx for Recorded foot length was available for of the stillborn fetuses In cases The well-dated subset with available foot length included The difference between the GA at death calculated by the algorithm and the GA calculated by foot length alone is shown in Table 4.

The remaining 47 cases differed by at least three weeks range 3—8 weeks. The algorithm that is described to estimate GA at death in cases of stillbirth incorporates readily available clinical data and simple examination of the infant after delivery. Optimal determination of the GA at fetal death is important for the accuracy of vital statistics, for identifying epidemiologic patterns and risk factors for stillbirth at various stages of gestation, and for correctly identifying growth abnormalities.

In our study, precise assignment of GA at death was possible in just under half of our cases Given the geographic and racial diversity of our catchment areas, this is likely representative of general clinical practice in the United States. Use of fetal foot length provided important and valid information with which GA at death could be estimated in cases with unreliable dating criteria, and we recommend that foot length be measured and recorded in all stillbirth cases. Similarly, other investigators have validated the correlation between fetal foot length and gestational age, whether measured prenatally by ultrasound 14 — 16 , or in postmortem examinations 4 , This is an important finding for two reasons.

First, more than half the cases of stillbirth in this population-based study lacked precision of one or both of the key pieces of information needed to pinpoint the GA at death: Second, fetal foot length can be measured easily at the time of delivery of the stillborn infant, and its conversion to GA requires no specialized expertise or equipment. Thus, even when families decline a comprehensive postmortem examination, this critical information can be ascertained.

This finding has implications for vital statistics reporting, as well as for determining the contribution of abnormal fetal growth to the etiology of stillbirth. Over- or underestimation of GA at death renders interpretation of birth weight percentiles inaccurate, potentially distorting the role of fetal growth restriction or accelerated growth in the pathogenesis of fetal death. Therefore, the contribution of fetal growth restriction to stillbirth might be less than previously reported.

Indeed, spontaneous labor occurred in eight cases after fetuses had been retained for 39—90 days after absence of fetal heart sounds.

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Use of the algorithm to estimate GA at death is likely to be less accurate for women with little prenatal care prior to stillbirth. These factors may affect reliability of dating criteria as well as estimates of the TOD interval. Where precise dating and timing of death are not possible, reliance on foot length to estimate GA at death may also contribute to under- or overestimation of GA in some cases, with consequences for determining fetal growth.

Reporting of fetal death is fraught with the potential for miscommunication and misinterpretation of clinical data regarding gestational age and timing of death. Healthcare providers and hospital personnel who are responsible for providing this information generally do not have access to guidelines written in plain language or training in accurate collection of data and completion of reporting forms. Relying on individual interpretation of proper procedures for completing standardized reporting forms can result in incomplete or erroneous data. Moreover, an improved estimate of the gestational age at fetal death would be a desirable addition to vital statistics reporting.

The algorithm described here can be easily applied in day-to-day clinical practice. First, every effort should be made to corroborate or revise historical pregnancy dating criteria e. Second, the date of the most recent objective evidence of fetal life should be documented and compared to the date of diagnosis of the stillbirth to determine the range of dates during which the stillbirth occurred.

Presence or absence of maceration can be assessed by visual examination at the time of delivery. Exceptions may include cases with known aneuploidy or significant fetal anomalies, as well as those where delayed fetal growth had been identified by ultrasound while the fetus was alive. Foot length, while the best available fetal measure for gestational age determination, is affected by lack of or excessive fetal growth Corroborating pathologic data with the known clinical scenario of each stillbirth is important.

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For example, several stillborn fetuses in our well-dated subset with the largest discrepancy between foot length and known gestational age at time of death were found to have severe IUGR by sonogram preceding fetal death. There is no gold standard for estimating the gestational age of fetal death. Estimation must employ common-sense application of currently available knowledge and tools.

Using our algorithm, imprecise timing of fetal death or unreliable dating criteria prevented precise determination of the gestational age of fetal death for more than half the cases of stillbirth.

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Nonetheless, our results suggest that the accuracy and uniformity of the information collected can be improved through the use of this algorithm. Rowland Hogue, Barbara J. National Center for Biotechnology Information , U. Author manuscript; available in PMC Mar 1. Author information Copyright and License information Disclaimer. The publisher's final edited version of this article is available at Paediatr Perinat Epidemiol.


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See other articles in PMC that cite the published article. Abstract Background Accurate assignment of gestational age at time of fetal death is important for research and clinical practice. Step 1—Estimating the due date The estimated due date EDD was assigned using the last menstrual period LMP date derived from chart abstraction and the earliest dated obstetric ultrasound where the baby was alive, if available. If both a dated ultrasound report, where the fetus was alive and a LMP date were available, the clinical reliability of the LMP date was considered.

Open in a separate window. To better match expected determination of agreement in a clinical setting, 0. Combining Lmp and Ultrasound Data to Determine Estimated Due Date This figure depicts the first step in the algorithm which is to determine the best estimated due date using clinical history and imaging findings. Step 3—Estimating GA at fetal death The algorithm estimated the GA at fetal death and the date of death by incorporating several factors: Reliability of foot length We identified a well-dated subset of the stillbirth cases with both clinically reliable gestational dating criteria and a short timing of death interval, and who had a foot length measurement recorded.

Statistical Analysis Summary statistics were used to describe the results. Table 1 provides guidelines for estimating the due date based on ultrasonography and the LMP in pregnancy, and provides single-point cutoffs and ranges based on available evidence and expert opinion. No part of this publication may be reproduced, stored in a retrieval system, posted on the Internet, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.

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Methods for estimating the due date. American College of Obstetricians and Gynecologists. Women's Health Care Physicians. Recommendations The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine make the following recommendations regarding the method for estimating gestational age and due date: As soon as data from the last menstrual period LMP , the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.

Introduction An accurately assigned EDD early in prenatal care is among the most important results of evaluation and history taking. Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as the biparietal diameter and head circumference measured in transverse section of the head at the level of the thalami and cavum septi pellucidi; the cerebellar hemispheres should not be visible in this scanning plane the femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis the abdominal circumference measured in symmetrical, transverse round section at the skin line, with visualization of the vertebrae and in a plane with visualization of the stomach, umbilical vein, and portal sinus 8 Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role.

Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. Fetal Imaging Workshop Invited Participants. A comparison of recalled date of last menstrual period with prospectively recorded dates. J Womens Health Larchmt ; Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol ; Last menstrual period versus ultrasound for pregnancy dating.

Int J Gynaecol Obstet ; First trimester ultrasound screening is effective in reducing postterm labor induction rates: Ultrasound for fetal assessment in early pregnancy.

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Cochrane Database of Systematic Reviews , Issue 7. Predicting delivery date by ultrasound and last menstrual period in early gestation.


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  5. New charts for ultrasound dating of pregnancy and assessment of fetal growth: Ultrasound Obstet Gynecol ; First- and second-trimester ultrasound assessment of gestational age. First- vs second-trimester ultrasound: Br J Obstet Gynaecol ; Gestational age in pregnancies conceived after in vitro fertilization: Ultrasound dating at 12—14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies. Accuracy of gestational age estimation by means of fetal crown—rump length measurement.

    Estimation of gestational age by transvaginal sonographic measurement of greatest embryonic length in dated human embryos. Ultrasound Obstet Gynecol ;4: Underestimation of gestational age by conventional crown—rump length dating curves. New crown—rump length curve based on over pregnancies. Standardization of sonar cephalometry and gestational age. Sonographic prediction of gestational age: Conceptional age, menstrual age, and ultrasound age: Computer assisted analysis of fetal age in the third trimester using multiple fetal growth parameters.