Gestational dating ultrasound

Ultrasound for gestation dating diagnosis code

Ultrasound for gestation dating diagnosis code

Gestational age, synonymous with menstrual age, is defined in weeks beginning from the first day of the last menstrual period LMP prior to conception. Accurate determination of gestational age is fundamental to obstetric care and is important in a variety of situations. For example, antenatal test interpretation may be dependent on gestational age. Specifically, the level of α-fetoprotein in both amniotic fluid and maternal serum is related to gestational gestational dating ultrasound and when dates are inaccurate test results will be incorrect and misleading.

Similarly, the magnitude of increased optical density above baseline at 450 nm delta OD 450 by amniotic fluid spectrophotometric measurement is used to predict the severity of fetal hemolytic disease in pregnancies complicated by rhesus isoimmunization.

Again, inaccurate assessment of gestational age will lead to errors in assessing the severity of fetal sensitization by the delta OD 450.

Fetal growth assessment, either clinically or by ultrasound evaluation, also relies on accurate assessment of gestational age. Fetal growth retardation or macrosomia may be gestational dating ultrasound or incorrectly diagnosed owing to errors in gestational age assignment. Interpretation of antenatal biophysical testing non-stress tests and biophysical profiles may be subject to variation with gestational age as well.

Fetal heart rate reactivity and fetal breathing develop with advancing gestational age; therefore, the absence of these biophysical parameters may be interpreted as abnormal for fetuses in whom the gestational age has been overestimated. Obstetric management is also dependent on gestational age. Proper decisions gestational dating ultrasound presumed preterm labor or postdate pregnancies are only possible when gestational age is accurately estimated.

Likewise, timing of repeat cesarean section requires accurate assessment of dates. In the past gestational age was established by a combination of the historical information and the physical gestational dating ultrasound.

Other factors include assessment of uterine size by bimanual examination in the first trimester, initial detection of fetal heart tones by Doppler 10—12 weeks or auscultation 19—21 weeksand uterine fundal height measurement. However, both the history and the findings on physical examination are fraught with error, even in the best of circumstances. Hertz and co-workers reported that menstrual history was considered reliable in only 18% of women.

In another report, even among women with known LMP, neonatal age assessment differed markedly from that assigned by certain menstrual dates in 15%.

Physical examination also tends to be inaccurate, especially with advancing gestational age. Bimanual examination in the first trimester may be accurate within ±2 weeks; however, fundal height measurement, which is more commonly used to assess gestational age, is only accurate within ±4 to 6 weeks. Clearly, the inaccuracies of history and physical examination may limit their usefulness in assessment of gestational age.

Methods that assess the time of ovulation or conception can accurately establish gestational age. Ovulation induction with agents such as clomiphene citrate and Pergonal, also accurately predicts gestational age. In vitro fertilization, with known date of conception, is likely the most accurate means of predicting gestational age ±1 day.

However, in most pregnancies, the date of ovulation or conception cannot be as accurately predicted as outlined above and gestational age gestational dating ultrasound be established by other methods. Measurements of a wide variety of parameters have been devised to establish gestational dating ultrasound age. Ultrasound assessment of gestational age is feasible in a majority of pregnancies and may be used to establish gestational age with gestational dating ultrasound accuracy than physical examination.

In the first trimester, gestational sac mean diameter and crown-rump length measurements have become the primary means of evaluating gestational age. Those parameters most commonly measured include biparietal diameter,, head circumference,abdominal circumference, and femur length.

First-Trimester Assessment In the first trimester, the gestational sac mean diameter and crown-rump length are used to establish fetal age.

Both parameters are useful because each measures a different aspect of the first-trimester pregnancy and may be used at different times during the first trimester.

GESTATIONAL SAC MEAN DIAMETER. The gestational sac is the first identifiable structure routinely imaged in the first trimester. It is identified by transabdominal ultrasound as early as 5 weeks' gestation and may be seen as early as 4 weeks' gestation by transvaginal ultrasound. The sac is measured inside the hyperechoic rim, including only the echo-free space Fig. The gestational sac is imaged first in the longitudinal plane, obtaining long axis and anteroposterior measurements perpendicular to each other.

Then, in the transverse plane at the level of the anteroposterior measurement, the width measurement is obtained. The three measurements are averaged to obtain the gestational sac mean diameter. The accuracy of gestational sac measurement as a predictor of gestational age has been evaluated in only one report and was found to be approximately ±1 week. Gestational Sac Mean Diameter Measurements Relative to Gestational Age Gestational Sac Gestational Age Gestational Sac Gestational Age Mean Diameter mm weeks Mean Diameter mm weeks 10 5.

Am J Obstet Gynecol 103:789, 1969. Reprinted with permission of CV Mosby, St. Longitudinal image of a gestational sac. The longitudinal diameter is measured between the small crosses 1 and the anteroposterior diameter is measured between the larger crosses 2.

Transverse image gestational dating ultrasound at the level of the anteroposterior diameter. The transverse diameter is measured between the crosses. The crown-rump length CRL is a measurement of the embryo, usually identified at 6 to 7 weeks' gestation. Gestational dating ultrasound length may be used to accurately date pregnancy between 7 and 13 weeks' gestation. The technique involves measurement of the fetal length from the tip of the cephalic pole to the tip of the caudal pole.

The fetus should be at rest and assuming its natural curvature. At 5 to 6 weeks' gestation, distinct landmarks cannot always be identified but heart motion usually can be detected centrally. As the pregnancy continues, the head can be easily identified from the rest of the body. After 12 weeks' gestation excessive curvature of the fetus may lead to erroneous shortening of CRL measurement; therefore, other measurements, such as the biparietal diameter, should be used to estimate gestational age.

Ultrasound image of a gestational dating ultrasound at 10 weeks' gestation. The crown-rump length is measured along the longest axis of the fetus between the arrows The correlation between sonographic CRL values and dates was first reported by Robinson and Fleming, who obtained CRLs in pregnancies of women with certain menstrual histories.

Drumm and associates performed a similar study; however, their patients fulfilled more stringent dating criteria. These early studies suggested that gestational age assessment by CRL was extremely accurate, approaching ±3 to 4 days. Subsequent studies have suggested that the CRL is somewhat less accurate; however, the accuracy is still within ±5 to 7 days.

Crown-Rump Length Measurements Relative to Gestational Age in Three Studies MacGregor et Robinson and Drumm et Gestational dating ultrasound alGestational Age FlemingGestational Age alGestational Age Length cm Weeks + Days Weeks + Days Weeks + Days 1. Obstet Gynecol 70:344, 1987. Reprinted with permission of American College of Obstetricians and Gynecologists Variations in the measurement of CRL can be attributed to differences in fetal growth patterns. Such differences are related to factors similar to those that influence birth weight curves, including maternal age and parity, prepregnancy maternal weight, geographic location, and population characteristics.

These include incorporation of the yolk gestational dating ultrasound or lower limbs in the CRL measurement, excessive curling or extension of the fetus, and tangential section of the trunk. Despite gestational dating ultrasound potential sources of error, CRL measurement is an accurate and useful method of assessing gestational age in the first trimester. Second- and Third-Trimester Assessment BIPARIETAL DIAMETER. The biparietal gestational dating ultrasound BPD is one of the most commonly measured parameters in the fetus.

Campbell was the first investigator to link fetal BPD to gestational age; however, since this original report, numerous publications on this subject have appeared in the literature. The BPD is imaged in the transaxial plane of the fetal head at a level depicting thalami gestational dating ultrasound the midline, equidistant from the temporoparietal bones and usually the cavum septum pellucidum anteriorly Fig.

Transaxial image of the fetal head for biparietal diameter and head circumference measurements. Ultrasound image with biparietal diameter measurement between the solid arrows, outer edge to gestational dating ultrasound edge and fronto-occipital diameter measurement between the open arrows. The gestational dating ultrasound circumference may be calculated using these diameters or measured directly. Diagram of the transaxial ultrasound image of the fetal head at the level of the thalami large arrowsmidline falx curved arrowand cavum septi pellucidi open arrow.

Gestational age assignment is based on the mean BPD; however, a single BPD encompasses a range of ages in which most fetuses of that size are most likely to fall. The accuracy of fetal age assessment based on BPD is dependent on gestational age. After 26 weeks' gestation, the accuracy of BPD measurement progressively decreases and is ±3 weeks near term. A number of factors may contribute to variation or inaccuracy in the BPD measurement.

Biologic variation, for example, may occur because of differences in maternal age, parity, prepregnancy weight, geographic location, and specific population characteristics.

Technical factors including interobserver error, different techniques of measurements, and single versus multiple measurements may likewise influence the accuracy of BPD in assessing gestational age. Furthermore, BPD measurement is most accurate in assessing gestational age when the head shape is appropriately ovoid. If the head is unusually rounded brachycephalic or unusually elongated dolicocephalicBPD measurements would overestimate or underestimate gestational age, respectively.

To determine whether head shape is appropriate, Hadlock and co-workers compared the BPD and the frontooccipital diameter. The ratio of these diameters is called the cephalic index CIwith a mean value of 0.

Biparietal Diameter Measurements Relative to Gestational Age Menstrual Menstrual BPD cm Age weeks BPD cm Age weeks 2. Obstet Gynecol 52:402, 1978. Reprinted with permission of American College of Obstetricians and Gynecologists HEAD CIRCUMFERENCE. The head circumference HC measurement may be used to estimate gestational age in a similar manner to BPD measurement.

Although tracing of the outer perimeter of the head gestational dating ultrasound trackball on the ultrasonic equipment or by digitizer is the most reliable means of measuring HC, the following formula using biparietal gestational dating ultrasound fronto-occipital diameters may be used to calculate HC with a maximum error of 6%:TABLE 5.

Head Circumference Measurements Relative to Gestational Age Gestational dating ultrasound Menstrual Head Menstrual Circumference Age Circumference Age cm weeks cm weeks 8. The accuracy of gestational age estimation by HC measurement is comparable with that of BPD measurement. However, in fetuses with abnormal head shape, either brachycephaly or dolicocephaly, HC may be a more accurate predictor of fetal age than BPD. Measurement of the fetal abdominal circumference AC is obtained in the transaxial view of the fetal abdomen.

The AC is measured at the level of the fetal liver, using the umbilical portion of the left portal vein as a landmark Fig. The fetal stomach is at the same level, which is slightly caudad to the gestational dating ultrasound heart and cephalad to the kidneys. The AC measurement is taken from the outermost aspects of gestational dating ultrasound fetal soft tissues. Measurement of the AC is performed in the same manner as that of the HC, that is, by 1 tracing the outer perimeter of the AC by the trackball on the ultrasonic equipment or by digitizer or 2 the same equation as for HC using transverse and anteroposterior diameters of the fetal abdomen.

The AC may be used to estimate gestational age but is less accurate than head measurements BPD or HC. Similar to head measurements, the accuracy of AC in estimating gestational age is greatest in the second trimester, with decreasing accuracy near term. Biologic variation and technical factors may contribute to the inaccuracy of AC measurements in a manner similar to that previously described for bi-parietal diameters.

Of particular note, the abdominal circumference is the growth parameter most commonly affected in pregnancies complicated by abnormal fetal growth patterns. A macrosomic fetus will have increased AC relative to gestational age, and an asymmetrically growth-retarded fetus will have diminished AC measurements.

Variation in AC measurements in macrosomic and growth-retarded fetuses is due to differences in liver size and width of subcutaneous tissue in these two types of abnormal growth patterns. Thus, estimation of gestational age by AC will lead to inaccuracies in fetuses displaying either of these growth patterns.

Abdominal Circumference Measurements Relative to Gestational Age Abdominal Menstrual Abdominal Menstrual Circumference Age Circumference Age cm weeks cm weeks 10.

Br J Obstet Gynaecol 84:165, 1977. Reprinted with permission of Blackwell Scientific Publications, Oxford, England. Transaxial image of the upper fetal abdomen. Ultrasound image with anteroposterior solid arrows and transverse open arrows diameter measurements. The abdominal circumference may be calculated using these diameters or measured directly. Diagram of the transaxial ultrasound image gestational dating ultrasound the fetal abdomen at the level of the abdominal circumference measurement with fetal spine curved arrowthe umbilical portion of the left portal vein solid arrowand fetal stomach open arrow FEMUR LENGTH.

All the fetal long bones can be adequately examined and measured by ultrasound; however, the femur is the largest of the long bones, least moveable, and easiest to image. The femur may be adequately visualized from 14 weeks' gestation until delivery. The femoral neck and both proximal and distal epiphyseal cartilages are excluded from the measurement.

Femur length FL measurements may be used to accurately predict gestational age between 14 weeks' gestation and term. Most observers consider the accuracy of the FL and BPD measurements to be similar in the third trimester. Although there is controversy regarding the accuracy of the FL prior to 26 weeks' gestation,the accuracy of gestational age prediction based on FL is greatest in the second trimester and least near term.

Femur Length Measurements Relative to Gestational Age Femur Menstrual Femur Menstrual Length Age Length Age cm weeks cm weeks 1. Linear array image of the fetal femur. The femur length is measured between the arrows. Biologic variation may lead to inaccuracies of FL measurements in a manner similar to that of the other fetal growth parameters.

In addition, several technical factors are potential sources of error in the measurement of the femur. Linear-array ultrasound imaging provides more accurate measurements of FL. In addition, FL measurements obtained in the axial plane parallel to the ultrasonic beam have less mean absolute error than those obtained in the lateral plane, perpendicular to the ultrasonic beam 1. Tangential section of the femur, failing to visualize the entire length of the shaft, leads to underestimation of FL and, therefore, of gestational age.

Artifactual bowing of the femur may also occur on ultrasound imaging and lead to a shortened FL measurement. The distal femoral epiphysis becomes echogenic in the third trimester and is separated from the distal end of the diaphysis, the osseous portion of the shaft. Inclusion of the distal epiphysis will falsely overestimate FL. The accuracy of a single parameter is dependent on the gestational age at the time of ultrasound examination. Several methods have been employed to improve the accuracy of gestational age assessment compared with the use of a single parameter.

Two of these methods, growth-adjusted sonographic age and averaging multiple parametersare discussed. Several principles are important to remember when assessing gestational age by ultrasound: TABLE 9.

Growth-Adjusted Sonographic Age Gestational age estimation using a single biparietal diameter is accurate within a margin of ±10 to 11 days in the second trimester. Gestational age can be more accurately predicted by obtaining paired BPD measurements the first from 20 to 26 weeks' gestation and the second from 31 to 33 weeks' gestation and assigning gestational age by a method developed by Sabbagha and co-workers known as growth-adjusted sonographic age GASA.

In approximately 90% of fetuses, BPD growth from 20 to 33 weeks' gestation tends to progress within narrow percentile ranks. Paired BPD measurements obtained at different gestational ages allows categorization of the specific cephalic growth pattern. The first measurement should be obtained between 20 and 26 weeks' gestation, and the second measurement gestational dating ultrasound be obtained between 30 and 33 weeks' gestation. The first BPD measurement will not distinguish the fetus with large, average, or small BPD growth, and, therefore, the fetus is assigned a mean gestational age based on an assumed average BPD growth pattern.

The second BPD measurement identifies the specific type of growth pattern. For example, in the fetus with average growth the second BPD measurement will fall between the 10th and 90th percentiles, confirming the gestational age assignment from the first BPD measurement. In contrast, BPD growth in the small-for-gestational age fetus will follow a slow growth pattern and the second BPD measurement will be less than or equal to the 10th percentile for the gestational age assigned by the first BPD.

Since the first BPD measurement failed to recognize the small growth pattern and, therefore, underestimated gestational age, the second measurement allows the gestational age assessment to be adjusted based on the BPD growth pattern. Such a fetus with a slowed growth pattern would have the gestational age advanced by 1 week at the time of the second BPD measurement.

Similarly, dates in the large-for-gestational age fetus may be adjusted by GASA at the time of the second BPD measurement, decreasing gestational age assignment by 1 week if the BPD measurement is greater than or equal to the 90th percentile Fig. Use of GASA has been reported to increase the accuracy of gestational age estimation by BPD measurement to within ±3 to 5 days.

Obstet Gynecol in press. Reprinted with permission of American College of Obstetricians and Gynecologists. Fetal growth patterns from second trimester BPD of 5. The first BPD of 5. A second BPD measurement 10 weeks gestational dating ultrasound will identify the fetus as large 90 th percentileaverage between 10 th and 90 th percentilesor small 10 th percentile and lead to a closer assessment of fetal age. Sabbagha RE, Barton BA, Barton FB et al: Sonar biparietal diameter: II.

Predictive of three fetal growth patterns leading to a closer assessment of gestational dating ultrasound age and neonatal weight.

Am J Obstet Gynecol 126:485, 1976. Reprinted with permission of C. The method of GASA has not been used when the first BPD measurement is obtained prior to 20 weeks' gestation; therefore, it is best to confine the use of GASA to pregnancies in which serial ultrasound studies are contemplated and the first measurement is obtained between 20 and 26 weeks' gestation.

Smazal and associates evaluated the method of GASA and suggested that the accuracy was indeed ±5 days. However, in this report, the accuracy of a single BPD was also approximately ±5 days.

Multiple Fetal Growth Parameters Hadlock and co-workerscombined several measurements in an effort to increase the accuracy of gestational age assessment. The rationale for employing multiple parameters for fetal dating is that when two or more parameters predict the same end point, the probability of correctly predicting that end point is increased.

The BPD, HC, AC, and FL measurements were obtained and the mean gestational ages of combinations of these parameters were averaged to obtain a mean gestational age.

The use of multiple parameters improved the accuracy of gestational age assessment compared with any single parameter. If the gestational age estimates derived from all of the parameters are similar, assignment of gestational age from the average of all the parameters will improve accuracy. However, if gestational age estimates of the various parameters are quite different, averaging multiple parameters will decrease the accuracy of the best predictor s. Averaging of fetal growth parameters should be avoided when certain conditions are suspected, such as fetal macrosomia, intrauterine growth retardation both symmetric and asymmetricand congenital anomalies skeletal dysplasias, hydrocephalus, and others.

Reprinted with permission of Radiological Society of North America, Oak Brook, IL. Multiple Gestations The detection of multiple gestations is important since multiple gestations gestational dating ultrasound at greater risk gestational dating ultrasound many complications, particularly fetal growth retardation.

Fetal biometric data are available for twin gestations,; however, triplet and quadruplet pregnancies have not been adequately studied owing to their infrequent occurrence. In general, ultrasound-derived fetal dating tables obtained for singleton pregnancies can be used accurately for twin pregnancies until approximately 30 weeks' gestation. Grumbach and co-workers have suggested that the femur continues to grow normally throughout pregnancy in twin gestations, while the head BPD and HC and abdominal AC growth gestational dating ultrasound decrease in the last 10 weeks of pregnancy.

Although further studies are required to confirm these findings, this study suggests that FL measurement may be a more reliable parameter to use for gestational age assessment in twin gestations during the third trimester. Gestational age estimations in twin pregnancies prior to 30 weeks' gestation should be performed in a similar manner to that for singleton pregnancies. SUMMARY Gestational dating ultrasound simple, but uniform approach to the evaluation of gestational age should be performed in all fetuses.

The ultrasound assessment of fetal age is based on the earliest ultrasound study, provided gestational dating ultrasound measurement is technically adequate. Early in gestation fetal measurements have the least variability and, therefore, are most likely to predict fetal age. In the first trimester, the CRL measurement is used to estimate gestational age, whereas in the second and third trimesters fetal head BPD and HCbody ACand extremity FL measurements are used to assess gestational age.

If CRL and menstrual dates are within the normal range of error of the measurement ±7 daysthe menstrual dates are used to establish fetal age. If menstrual dates are unknown, or the difference between menstrual dates and the mean gestational age predicted by single or multiple parameters is greater than the range of error of these measurements, gestational dating ultrasound age should be established using the best ultrasound predictors either single or multiple parameters or GASA method.

Menstrual dates should be used to establish fetal age if the mean gestational age predicted by multiple parameters is within the range of error of these measurements ±2—3 weeks.

In the pregnancy with unknown menstrual dates or a discrepancy between menstrual dates and mean gestational age predicted by multiple parameters of more than 3 weeks, fetal age should be estimated by gestational dating ultrasound multiple parameters method. However, the potential error of this method in the third trimester of pregnancy may not be acceptable. Obstetric management must appreciate this potential for error. For example, a patient presenting in spontaneous labor at 33 ± 3 weeks' gestation should be managed as if the pregnancy may be as little as 30 weeks' gestation, rather than as advanced at 36 weeks' gestation.

Similarly, the patient presenting for prenatal care at 39 ± 3 weeks' gestation, should be gestational dating ultrasound for the potential of postdates pregnancy. Use of the multiple parameters method of gestational dating ultrasound gestational age is valid when the gestational age estimates of the various ultrasound parameters are similar.

If the gestational age estimates of one or several parameters is greater than 2 weeks different than the estimates of the other parameters, either the abnormal ultrasound parameters should be excluded or a different method should be used to estimate gestational age. When the various ultrasound parameters predict different gestational ages the fetus should be further evaluated to explain these differences. For example, an abnormally small FL measurement may suggest short-limb defects, a large BPD may be secondary to hydrocephalus, and gestational dating ultrasound abnormally small or large AC measurement may suggest asymmetric intrauterine growth retardation or macrosomia, respectively.

In the instance of an abnormal cephalic index, the HC should be used to estimate gestational age, rather than the BPD measurement. In conclusion, gestational dating ultrasound of gestational age is fundamental to obstetric care and should be a carefully thought-out process. Assessment should depend on history and physical examination, as well gestational dating ultrasound ultrasound evaluation.

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How reliable is ultrasound due date dating?

If you cant remember the date of your last menstrual period date, an early ultrasound can give you a fairly reliable due date. Ultrasound dating is also helpful if your menstrual cycles are irregular.

FIRST ULTRASOUND!! 8 WEEKS PREGNANT 👶🏻

Do ultrasounds change from early to late pregnancy?

Ultrasounds in Later Pregnancy. Earlier ultrasounds are more accurate in terms of predicting the due date, so thats why doctors will usually use the dates and measurements from the first ultrasound of the pregnancy as a reference. As the pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases.

What is an ultrasound in early pregnancy?

Ultrasound in early pregnancy (before 12 weeks) –Dating Scan Ultrasound in early pregnancy Ultrasound:  ‘Is a scan that uses sound waves to create a

What is an early ultrasound date?

Ultrasound dating is also helpful if your menstrual cycles are irregular. If an early ultrasound gives you a due date that is more than 1.2 weeks away from what was expected, there is a good chance that everything is still fine.

FIRST ULTRASOUND!! 8 WEEKS PREGNANT 👶🏻

Can due date be predicted with ultrasound?

If the date is not known, using LMP to establish the date can overestimate the duration of pregnancy. Thus, the due date predicted with the help of ultrasound is different from the one based on LMP. The ultrasound assessment is comparatively accurate in most cases, especially when the scans are done between six to ten weeks.

How accurate is an ultrasound at 20 weeks?

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. Early ultrasound due dates have a margin of error of roughly 1.2 weeks, so doctors will usually keep the original due date...

Are earlier ultrasounds more accurate in predicting pregnancy?

Earlier ultrasounds are more accurate in terms of predicting the due date, so thats why doctors will usually use the dates and measurements from the first ultrasound of the pregnancy as a reference.

What is an early ultrasound date?

Ultrasound dating is also helpful if your menstrual cycles are irregular. If an early ultrasound gives you a due date that is more than 1.2 weeks away from what was expected, there is a good chance that everything is still fine.

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