To receive news and publication updates for BioMed Research International, enter your email address in the box below. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Clear guidance on fetal growth assessment is important because of the strong links between growth restriction or macrosomia and adverse perinatal outcome in order to reduce associated morbidity and mortality. Fetal growth curves are extensively adopted to track fetal sizes from the early phases of pregnancy up to delivery. In the literature, a large variety of reference charts are reported but they are mostly up to five decades old. Furthermore, they do not address several variables and factors e.
Measurements of the CRL are more accurate the earlier in the first trimester that ultrasonography is performed 11, 15— The measurement used for dating should be the mean of three discrete CRL measurements when possible and should be obtained in a true midsagittal plane, with the genital tubercle and fetal spine longitudinally in view and the maximum length from cranium to caudal rump measured as a straight line 8, Mean sac diameter measurements are not recommended for estimating the due date.
Dating changes for smaller discrepancies are appropriate based on how early in the first trimester the ultrasound examination was performed and clinical assessment of the reliability of the LMP date Table 1. For instance, the EDD for a pregnancy that resulted from in vitro fertilization should be assigned using the age of the embryo and the date of transfer. For example, for a day-5 embryo, the EDD would be days from the embryo replacement date.
New charts for ultrasound dating of pregnancy and assessment of fetal growth
Likewise, the EDD for a day-3 embryo would be days from the embryo replacement date. Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation.
With rare exception, if a first-trimester ultrasound examination was performed, especially one consistent with LMP dating, gestational age should not be adjusted based on a second-trimester ultrasound examination.
Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as.
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Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role. Date changes for smaller discrepancies 10—14 days are appropriate based on how early in this second-trimester range the ultrasound examination was performed and on clinician assessment of LMP reliability.
Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close surveillance, including repeat ultrasonography, to ensure appropriate interval growth.
The best available data support adjusting the EDD of a pregnancy if the first ultrasonography in the pregnancy is performed in the third trimester and suggests a discrepancy in gestational dating of more than 21 days. As soon as data from the 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.
For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the LMP alone, should be used as the measure for gestational age. The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine recognize the advantages of a single dating paradigm being used within and between institutions that provide obstetric care. 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. 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.
The HC was measured fitting a computer-generated ellipse to include the outer edges of the calvarial margins of the fetal skull.
The abdominal circumference AC was measured fitting a computer-generated ellipse through a transverse section of the fetal abdomen at the level of the stomach and bifurcation of the main portal vein into its right and left branches. The femur length FL was measured in a longitudinal scan where the whole femural diaphysis was seen almost parallel to the transducer and measured from the greater trochanter to the lateral condyle.
In the third trimester, particular care was taken not to include the epiphysis. Each interval of gestational age was centred on a week, so that from 13 weeks and 4 days up to 14 weeks and 3 days has been considered as 14th week.
Statistical analysis has been performed using appropriate packages of R Software http: The normality of measurements at each week of gestation was assessed using the Shapiro-Wilk test [ 21 ], which is one of the most powerful tests to use for the normality assessment, especially for small samples. It tests the null hypothesis that a given sample came from a normally distributed population. In order to obtain normal ranges for fetal measurements, a multistep procedure based on regression model has been used, according to the recommended methodology for this type of data [ 22 , 23 ].
Assuming that, at each gestational age, the measurement of interest has a Gaussian distribution with a mean and a standard deviation SD and that, in general, both vary smoothly with gestational age, a centile curve has been calculated using the well-known formula: The mean has been estimated by the fitted values from an appropriate polynomial regression curve of the measurement of interest on gestational age.
Several curve-fitting and smoothing techniques have been tested for the mean estimation of the different biometric parameters and the goodness of fit for each regression model has been carefully assessed. The polynomial model that better satisfies the experimental data is the cubic one, since it better fulfils the fractional polynomial and the logarithmic transformations.
These residuals are the differences between the measurements and the estimated curve for the mean with the sign removed and multiplied by a corrective constant equal to.
Generally, if the scaled absolute residuals appear to show no trend with gestational age, the SD is estimated as the standard deviation of the unscaled residuals measurements minus the estimated mean curve. If there is a trend, then polynomial regression analysis is needed to estimate an appropriate curve in the same way of the mean. For BPD, HC, and AC biometric parameters, the residuals were regressed on gestational ages by using a linear model in the form of While, considering the FL parameter, the quadratic regression seems to better fulfil the linear one.
The adopted equation is Finally, these predictive mean and SD equations allow calculating any required centile, replacing the value in the centile formula. Data analysis showed that neither the use of fractional polynomials the greatest power of the polynomials being 3 nor the logarithmic transformation improved the fitting of the curves. Therefore, the data were kept in their original scale.
To choose the best fitting model, we have taken into consideration primarily the index which is the linear determination index: Other factors we have considered include the validity and the effectiveness of the model.
There will be an improvement in fit as higher-order terms are added, but because these terms are not theoretically justified, the improvement will be sample-specific.
Unless the sample is very small, the fits of higher-order polynomials are unlikely to be very different from those of a quadratic over the main part of the data range. Consider that, for example, the for the quadratic specification of BPD parameter is 0.
Further, the cubic and quartic curves both exhibit implausible strange twists at the extremities Figures 1 and 2. The scatter of absolute residuals from the regression for estimation of the standard deviation of femur length as a function of gestational age is shown in Figure 3.
The corresponding regression equations, with the respective index for the mean and the standard deviation, are illustrated in Table 1.How to Calculate Your Due Date in Pregnancy - Pregnancy Due Date Calculator
In each table, it is also indicated that the sample number, the mean, and the standard deviation are related to each gestational week. In order to validate the system, authors have performed an initial technical test with a growth curve simulator able to respect the mean and the standard deviation that characterize the Gaussian distribution for a specific patient age. The generated data allowed authors to prove the correctness of the elaboration of the fetal growth curves model.
After this preliminary analysis, authors have performed a test on the field considering about US pictures related to Italian women undergoing ultrasound examination between the 11th and 41th weeks of gestation at Vito Fazzi Hospital, Lecce, between November and September The obtained curves were then compared with those developed by Giorlandino et al. The AC and HC biometric parameters seem to follow more or less the same Italian and European trend according to the gestational age.
In fact, no significant differences were observed in the values measured during the different growth stages. This variability may be better presented by means of scatterplot of Salentinian samples overlapped with the centile curves to verify the amount and the density of the samples that are outside the considered range. Considering the Italian reference centile curves depicted in Figure 6 , which represent, respectively, the 5th, 10th, 25th, 50th, 75th, 90th, and 95th, the Salentinian samples are always above the upper limit, especially in the last weeks of gestation.
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