Reference values Archives - Revista Brasileira de Ginecologia e Obstetrícia
Summary
Rev Bras Ginecol Obstet. 2013;35(1):33-38
DOI 10.1590/S0100-72032013000100007
PURPOSE: To create longitudinal reference intervals for pulsatility index (PI) of the umbilical (UA), middle cerebral (MCA), uterine (UtA) arteries and ductus venosus (DV) in a Brazilian cohort. METHODS: A longitudinal observational study performed from February 2010 to May 2012. Low risk pregnancies were scanned fortnightly from 18 to 40 weeks for the measurements of PI of the UA, MCA, DV and UtA. Linear mixed models were used for the elaboration of longitudinal reference intervals (5th, 50th and 95th percentiles) of these measurements. PI obtained for the placental and abdominal portions of the umbilical artery were compared by the t-test for independent samples. Two-sided p values of less than 0.05 were considered statistically significant. RESULTS: A total of 164 patients underwent 1,242 scans. There was significant decrease in PI values of all vessels studied with gestational age (GA). From the 18th to the 40th week of pregnancy, the median PI values of UA (abdominal and placental ends of the cord), MCA, DV and the mean PI of the UtA ranged from 1.19 to 0.74, 1.33 to 0.78, 1.56 to 1.39, 0.58 to 0.41, and 0.98 to 0.66, respectively. The following equations were obtained for the prediction of the medians: PI-UA=1.5602786 - (0.020623 x GA); Logarithm of the PI-MCA=0.8149111 - (0.004168 x GA) - [0.02543 x (GA - 28.7756)²]; Logarithm of the PI-DV=-0.26691- (0.015414 x GA); PI-UtA = 1.2362403 - (0.014392 x GA). There was a significant difference between the PI-UA obtained at the abdominal and placental ends of the umbilical cord (p<0.001). CONCLUSIONS: Longitudinal reference intervals for the main gestational Doppler parameters were obtained in a Brazilian cohort. These intervals could be more adequate for the follow-up of maternal-fetal hemodynamic modifications in normal and abnormal pregnancies, a fact that still requires further validation.
Summary
Rev Bras Ginecol Obstet. 2013;35(1):33-38
DOI 10.1590/S0100-72032013000100007
PURPOSE: To create longitudinal reference intervals for pulsatility index (PI) of the umbilical (UA), middle cerebral (MCA), uterine (UtA) arteries and ductus venosus (DV) in a Brazilian cohort. METHODS: A longitudinal observational study performed from February 2010 to May 2012. Low risk pregnancies were scanned fortnightly from 18 to 40 weeks for the measurements of PI of the UA, MCA, DV and UtA. Linear mixed models were used for the elaboration of longitudinal reference intervals (5th, 50th and 95th percentiles) of these measurements. PI obtained for the placental and abdominal portions of the umbilical artery were compared by the t-test for independent samples. Two-sided p values of less than 0.05 were considered statistically significant. RESULTS: A total of 164 patients underwent 1,242 scans. There was significant decrease in PI values of all vessels studied with gestational age (GA). From the 18th to the 40th week of pregnancy, the median PI values of UA (abdominal and placental ends of the cord), MCA, DV and the mean PI of the UtA ranged from 1.19 to 0.74, 1.33 to 0.78, 1.56 to 1.39, 0.58 to 0.41, and 0.98 to 0.66, respectively. The following equations were obtained for the prediction of the medians: PI-UA=1.5602786 - (0.020623 x GA); Logarithm of the PI-MCA=0.8149111 - (0.004168 x GA) - [0.02543 x (GA - 28.7756)²]; Logarithm of the PI-DV=-0.26691- (0.015414 x GA); PI-UtA = 1.2362403 - (0.014392 x GA). There was a significant difference between the PI-UA obtained at the abdominal and placental ends of the umbilical cord (p<0.001). CONCLUSIONS: Longitudinal reference intervals for the main gestational Doppler parameters were obtained in a Brazilian cohort. These intervals could be more adequate for the follow-up of maternal-fetal hemodynamic modifications in normal and abnormal pregnancies, a fact that still requires further validation.
Summary
Rev Bras Ginecol Obstet. 2012;34(10):466-472
DOI 10.1590/S0100-72032012001000006
PURPOSES: To elaborate models for the estimation of fetal weight and longitudinal reference intervals of estimated fetal weight (EFW) using a sample of the Brazilian population. METHODS: Prospective observational study. Two groups of patients were evaluated: Group EFW (estimation of fetal weight): to elaborate (EFW-El) and validate (EFW-Val) a model for the prediction of fetal weight; Group LRI (longitudinal reference intervals): To elaborate (LRI-El) and validate (LRF-Val) conditional (longitudinal) percentiles of EFW. Polynomial regression analysis was applied to the data from subgroup EFW-El to elaborate a model for the estimation of fetal weight. The performance of this model was compared to those of previously published formulas. Linear mixed models were used for the elaboration of longitudinal reference intervals of EFW using data from subgroup LRI-El. Data obtained from subgroup LRI-Val were used to validate these intervals. RESULTS: Group EFW consisted of 458 patients (EFW-El: 367; EFW-Val: 91) and Group LRI consisted of 315 patients (LRI-El: 265; LRI-Val: 50). The model obtained for EFW was: EFW=-8.277+2.146xBPDxACxFL-2.449xFLxBPD². The performances of other models were significantly worse than those obtained with our formula. Equations for the prediction of conditional percentiles of EFW were derived from the longitudinal observation of patients of subgroup LRI-El and validated with data from subgroup LRI-Val. CONCLUSIONS: We described a method for customization of longitudinal reference intervals of EFW obtained using formulas generated from a sample of the Brazilian population.
Summary
Rev Bras Ginecol Obstet. 2012;34(10):466-472
DOI 10.1590/S0100-72032012001000006
PURPOSES: To elaborate models for the estimation of fetal weight and longitudinal reference intervals of estimated fetal weight (EFW) using a sample of the Brazilian population. METHODS: Prospective observational study. Two groups of patients were evaluated: Group EFW (estimation of fetal weight): to elaborate (EFW-El) and validate (EFW-Val) a model for the prediction of fetal weight; Group LRI (longitudinal reference intervals): To elaborate (LRI-El) and validate (LRF-Val) conditional (longitudinal) percentiles of EFW. Polynomial regression analysis was applied to the data from subgroup EFW-El to elaborate a model for the estimation of fetal weight. The performance of this model was compared to those of previously published formulas. Linear mixed models were used for the elaboration of longitudinal reference intervals of EFW using data from subgroup LRI-El. Data obtained from subgroup LRI-Val were used to validate these intervals. RESULTS: Group EFW consisted of 458 patients (EFW-El: 367; EFW-Val: 91) and Group LRI consisted of 315 patients (LRI-El: 265; LRI-Val: 50). The model obtained for EFW was: EFW=-8.277+2.146xBPDxACxFL-2.449xFLxBPD². The performances of other models were significantly worse than those obtained with our formula. Equations for the prediction of conditional percentiles of EFW were derived from the longitudinal observation of patients of subgroup LRI-El and validated with data from subgroup LRI-Val. CONCLUSIONS: We described a method for customization of longitudinal reference intervals of EFW obtained using formulas generated from a sample of the Brazilian population.
Summary
Rev Bras Ginecol Obstet. 2011;33(4):164-169
DOI 10.1590/S0100-72032011000400003
PURPOSE: to assess the validity of several fetal weight charts, commonly used in Portugal, to classify its population. METHODS: observational retrospective study. Singleton birth data was analyzed, from a two- year period (May 2008 to April 2010), from pregnancies with an ultrasound in the same institution, between the 8th and 14th gestational week. Upon data validation, percentiles for each completed gestational week were created, smoothed by a quadratic function, analyzed and compared to the tables more commonly utilized, in the institution and country, by using Z-scores, percentile comparison, sample 10th percentile detection sensibility and birthweight means comparison. RESULTS: a total of 5,378 newborns (NB) were born in the period; 2,195 (42%) NB were included, born from the 24th to 42nd gestational week, allowing statistical analysis from the 34th to the 41st week. There were differences in the mean birthweight for each gestational age, between references and with the sample, as well as between sexes. The 10th percentile from some references has shown differences ranging from -288g at 37 weeks (-11% in Lubchenco et al. data), with and +133g at 34 weeks (+7,6% with Carrascosa et al. data) compared to the values found with the sample. Differences were also found concerning the sensitivity of the identification of a sample birthweight below the 10th percentile, which was between 14.1 and 100%, depending on the reference used. DISCUSSION: the limitation of these kinds of reference values must be remembered and minimized, with the adoption of regionally or nationally produced references, contemplating other variables, such as sex, with precisely known gestation duration and with validation of the utilized references in loco.
Summary
Rev Bras Ginecol Obstet. 2011;33(4):164-169
DOI 10.1590/S0100-72032011000400003
PURPOSE: to assess the validity of several fetal weight charts, commonly used in Portugal, to classify its population. METHODS: observational retrospective study. Singleton birth data was analyzed, from a two- year period (May 2008 to April 2010), from pregnancies with an ultrasound in the same institution, between the 8th and 14th gestational week. Upon data validation, percentiles for each completed gestational week were created, smoothed by a quadratic function, analyzed and compared to the tables more commonly utilized, in the institution and country, by using Z-scores, percentile comparison, sample 10th percentile detection sensibility and birthweight means comparison. RESULTS: a total of 5,378 newborns (NB) were born in the period; 2,195 (42%) NB were included, born from the 24th to 42nd gestational week, allowing statistical analysis from the 34th to the 41st week. There were differences in the mean birthweight for each gestational age, between references and with the sample, as well as between sexes. The 10th percentile from some references has shown differences ranging from -288g at 37 weeks (-11% in Lubchenco et al. data), with and +133g at 34 weeks (+7,6% with Carrascosa et al. data) compared to the values found with the sample. Differences were also found concerning the sensitivity of the identification of a sample birthweight below the 10th percentile, which was between 14.1 and 100%, depending on the reference used. DISCUSSION: the limitation of these kinds of reference values must be remembered and minimized, with the adoption of regionally or nationally produced references, contemplating other variables, such as sex, with precisely known gestation duration and with validation of the utilized references in loco.
Summary
Rev Bras Ginecol Obstet. 2011;33(3):111-117
DOI 10.1590/S0100-72032011000300002
PURPOSE: to assess the distance of the fetal cerebral fissures from the inner edge of the skull by three-dimensional ultrasonography (3DUS). METHODS: this cross-sectional study included 80 women with normal pregnancies between 21st and 34th weeks. The distances between the Sylvian, parieto-occiptal, hippocampus and calcarine fissures and the internal surface of the fetal skull were measured. For the evaluation of the distance of the first three fissures, an axial three-dimensional scan was obtained (at the level of the lateral ventricles). To obtain the calcarine fissure measurement, a coronal scan was used (at the level of the occipital lobes). First degree regressions were performed to assess the correlation between fissure measurements and gestational age, using the determination coefficient (R²) for adjustment. The 5th, 50th and 95th percentiles were calculated for each fissure measurement. Pearson's correlation coefficient (r) was used to assess the correlation between fissure measurements and the biparietal diameter (BPD) and head circumference (HC). RESULTS: all fissure measurements were linearly correlated with gestational age (Sylvian: R²=0.5; parieto-occiptal: R²= 0.7; hippocampus: R²= 0.3 and calcarine: R²= 0.3). Mean fissure measurement ranged from 7.0 to 14.0 mm, 15.9 to 28.7 mm, 15.4 to 25.4 mm and 15.7 to 24.8 mm for the Sylvian, parieto-occiptal, hippocampus and calcarine fissures, respectively. The Sylvian and parieto-occiptal fissure measurements had the highest correlations with the BPD (r=0.8 and 0.7, respectively) and HC (r=0.7 and 0.8, respectively). CONCLUSION: the distance from the fetal cerebral fissures to the inner edge of the skull measured by 3DUS was positively correlated with gestational age.
Summary
Rev Bras Ginecol Obstet. 2011;33(3):111-117
DOI 10.1590/S0100-72032011000300002
PURPOSE: to assess the distance of the fetal cerebral fissures from the inner edge of the skull by three-dimensional ultrasonography (3DUS). METHODS: this cross-sectional study included 80 women with normal pregnancies between 21st and 34th weeks. The distances between the Sylvian, parieto-occiptal, hippocampus and calcarine fissures and the internal surface of the fetal skull were measured. For the evaluation of the distance of the first three fissures, an axial three-dimensional scan was obtained (at the level of the lateral ventricles). To obtain the calcarine fissure measurement, a coronal scan was used (at the level of the occipital lobes). First degree regressions were performed to assess the correlation between fissure measurements and gestational age, using the determination coefficient (R²) for adjustment. The 5th, 50th and 95th percentiles were calculated for each fissure measurement. Pearson's correlation coefficient (r) was used to assess the correlation between fissure measurements and the biparietal diameter (BPD) and head circumference (HC). RESULTS: all fissure measurements were linearly correlated with gestational age (Sylvian: R²=0.5; parieto-occiptal: R²= 0.7; hippocampus: R²= 0.3 and calcarine: R²= 0.3). Mean fissure measurement ranged from 7.0 to 14.0 mm, 15.9 to 28.7 mm, 15.4 to 25.4 mm and 15.7 to 24.8 mm for the Sylvian, parieto-occiptal, hippocampus and calcarine fissures, respectively. The Sylvian and parieto-occiptal fissure measurements had the highest correlations with the BPD (r=0.8 and 0.7, respectively) and HC (r=0.7 and 0.8, respectively). CONCLUSION: the distance from the fetal cerebral fissures to the inner edge of the skull measured by 3DUS was positively correlated with gestational age.
Summary
Rev Bras Ginecol Obstet. 2010;32(12):573-578
DOI 10.1590/S0100-72032010001200002
PURPOSE: to establish reference values for the length and area of the fetal corpus callosum between the 20th and 33rd weeks of gestation using three-dimensional ultrasound (3DUS). METHODS: this cross-sectional study involved 70 normal pregnancies with gestational age between 20 and 33 weeks. An Accuvix XQ instrument with a convex volumetric transducer (3 to 5 MHz) was used. To assess the corpus callosum, a transfrontal plane was obtained using the metopic suture as an acoustic window. Length was obtained by measuring the distance between the proximal and distal extremities of the corpus callosum. Area was obtained by manual tracing of the external corpus callosum surface. The means, medians, standard deviations, and maximum and minimum values were calculated for the corpus callosum length and area. Scatter graphs were created to analyze the correlation between corpus callosum length and area and gestational age and biparietal diameter, the quality adjustments was verified according to the determination coefficient (R²). The intraclass correlation coefficient (ICC) was used to assess the intraobserver variability. RESULTS: mean corpus callosum length increased from 21.7 (18.6 - 25.2 mm) to 38.7 mm (32.6 - 43.3 mm) between 20 and 33 weeks of pregnancy, respectively. Mean corpus callosum area increased from 55.2 (41.0 - 80.0 mm²) to 142.2 mm² (114.0 - 160.0 mm²), between 20 to 33 weeks of pregnancy, respectively. There was a strong correlation between corpus callosum length and area and gestational age (R² = 0.7 and 0.7, respectively) and biparietal diameter (R² = 0.7 and 0.6, respectively). Intraobserver variability was appropriate, with an ICC of 0.9 and 0.9 for length and area, respectively. CONCLUSIONS: reference values for corpus callosum length and area were established for fetuses between 20 and 33 weeks gestation. Intraobserver variability was appropriate.
Summary
Rev Bras Ginecol Obstet. 2010;32(12):573-578
DOI 10.1590/S0100-72032010001200002
PURPOSE: to establish reference values for the length and area of the fetal corpus callosum between the 20th and 33rd weeks of gestation using three-dimensional ultrasound (3DUS). METHODS: this cross-sectional study involved 70 normal pregnancies with gestational age between 20 and 33 weeks. An Accuvix XQ instrument with a convex volumetric transducer (3 to 5 MHz) was used. To assess the corpus callosum, a transfrontal plane was obtained using the metopic suture as an acoustic window. Length was obtained by measuring the distance between the proximal and distal extremities of the corpus callosum. Area was obtained by manual tracing of the external corpus callosum surface. The means, medians, standard deviations, and maximum and minimum values were calculated for the corpus callosum length and area. Scatter graphs were created to analyze the correlation between corpus callosum length and area and gestational age and biparietal diameter, the quality adjustments was verified according to the determination coefficient (R²). The intraclass correlation coefficient (ICC) was used to assess the intraobserver variability. RESULTS: mean corpus callosum length increased from 21.7 (18.6 - 25.2 mm) to 38.7 mm (32.6 - 43.3 mm) between 20 and 33 weeks of pregnancy, respectively. Mean corpus callosum area increased from 55.2 (41.0 - 80.0 mm²) to 142.2 mm² (114.0 - 160.0 mm²), between 20 to 33 weeks of pregnancy, respectively. There was a strong correlation between corpus callosum length and area and gestational age (R² = 0.7 and 0.7, respectively) and biparietal diameter (R² = 0.7 and 0.6, respectively). Intraobserver variability was appropriate, with an ICC of 0.9 and 0.9 for length and area, respectively. CONCLUSIONS: reference values for corpus callosum length and area were established for fetuses between 20 and 33 weeks gestation. Intraobserver variability was appropriate.
Summary
Rev Bras Ginecol Obstet. 2008;30(10):499-503
DOI 10.1590/S0100-72032008001000004
PURPOSE: to evaluate the embryo's volume (EV) between the seventh and the tenth gestational week, through tridimensional ultrasonography. METHODS: a transversal study with 63 normal pregnant women between the seventh and the tenth gestational week. The ultrasonographical exams have been performed with a volumetric abdominal transducer. Virtual Organ Computer-aided Analysis (VOCAL) has been used to calculate EV, with a rotation angle of 12º and a delimitation of 15 sequential slides. The average, median, standard deviation and maximum and minimum values have been calculated for the EV in all the gestational ages. A dispersion graphic has been drawn to assess the correlation between EV and the craniogluteal length (CGL), the adjustment being done by the determination coefficient (R²). To determine EV's reference intervals as a function of the CGL, the following formula was used: percentile=EV+K versus SD, with K=1.96. RESULTS: CGL has varied from 9.0 to 39.7 mm, with an average of 23.9 mm (±7.9 mm), while EV has varied from 0.1 to 7.6 cm³, with an average of 2.7 cm³ (±3.2 cm³). EV was highly correlated to CGL, the best adjustment being obtained with quadratic regression (EV=0.2-0.055 versus CGL+0.005 versus CGL²; R²=0.8). The average EV has varied from 0.1 (-0.3 to 0.5 cm³) to 6.7 cm³ (3.8 to 9.7 cm³) within the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval, while CGL, only 4.4 times. CONCLUSIONS: EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth week of gestation.
Summary
Rev Bras Ginecol Obstet. 2008;30(10):499-503
DOI 10.1590/S0100-72032008001000004
PURPOSE: to evaluate the embryo's volume (EV) between the seventh and the tenth gestational week, through tridimensional ultrasonography. METHODS: a transversal study with 63 normal pregnant women between the seventh and the tenth gestational week. The ultrasonographical exams have been performed with a volumetric abdominal transducer. Virtual Organ Computer-aided Analysis (VOCAL) has been used to calculate EV, with a rotation angle of 12º and a delimitation of 15 sequential slides. The average, median, standard deviation and maximum and minimum values have been calculated for the EV in all the gestational ages. A dispersion graphic has been drawn to assess the correlation between EV and the craniogluteal length (CGL), the adjustment being done by the determination coefficient (R²). To determine EV's reference intervals as a function of the CGL, the following formula was used: percentile=EV+K versus SD, with K=1.96. RESULTS: CGL has varied from 9.0 to 39.7 mm, with an average of 23.9 mm (±7.9 mm), while EV has varied from 0.1 to 7.6 cm³, with an average of 2.7 cm³ (±3.2 cm³). EV was highly correlated to CGL, the best adjustment being obtained with quadratic regression (EV=0.2-0.055 versus CGL+0.005 versus CGL²; R²=0.8). The average EV has varied from 0.1 (-0.3 to 0.5 cm³) to 6.7 cm³ (3.8 to 9.7 cm³) within the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval, while CGL, only 4.4 times. CONCLUSIONS: EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth week of gestation.
Summary
Rev Bras Ginecol Obstet. 2006;28(3):151-157
DOI 10.1590/S0100-72032006000300003
PURPOSE: the absence of fetal nasal bone is correlated with trisomy 21. Although a hypoplastic nasal bone is also correlated with trisomy 21, there is no clear definition of this term in the literature. Our objective was to establish the reference values for fetal nasal bone size throughout gestation in a local population in Brazil. METHODS: it is a cross-sectional study on 902 fetuses at 10 to 39 weeks of gestation. After having excluded fetal malformations and maternal diseases which are known to interfere with fetal growth, 625 fetuses were selected. We obtained a mid-sagittal view of the fetal profile by holding the ultrasound bean at an angle of 45º or 135º. The nasal bone size mean was calculated by using polynomial regression. The Anderson-Darling test proved the normal distribution of the measurements (p>0.05). RESULTS: of the 625 fetuses, 88.3% were from single gestations and 11.7% from multiple ones. There was a direct correlation between fetal nasal bone size and gestational age. The variability of nasal bone size became larger as gestational age increased. Minimal length of 1.0 and 4.7 mm in the first and second trimesters, respectively, were found. CONCLUSIONS: there is a direct correlation between fetal nasal bone size and gestational age. This correlation is valid either for a single gestation or a multiple one. These measurements of the fetal nasal bone will allow us to use them as a screening test for cromosomal abnormalities. This is a useful study if we consider the large miscegenation of the Brazilian population. However, further systematic and standardized approach to study the fetal nasal bone is needed to establish its real value in fetuses once classified as at high or low risk for aneuploidies.
Summary
Rev Bras Ginecol Obstet. 2006;28(3):151-157
DOI 10.1590/S0100-72032006000300003
PURPOSE: the absence of fetal nasal bone is correlated with trisomy 21. Although a hypoplastic nasal bone is also correlated with trisomy 21, there is no clear definition of this term in the literature. Our objective was to establish the reference values for fetal nasal bone size throughout gestation in a local population in Brazil. METHODS: it is a cross-sectional study on 902 fetuses at 10 to 39 weeks of gestation. After having excluded fetal malformations and maternal diseases which are known to interfere with fetal growth, 625 fetuses were selected. We obtained a mid-sagittal view of the fetal profile by holding the ultrasound bean at an angle of 45º or 135º. The nasal bone size mean was calculated by using polynomial regression. The Anderson-Darling test proved the normal distribution of the measurements (p>0.05). RESULTS: of the 625 fetuses, 88.3% were from single gestations and 11.7% from multiple ones. There was a direct correlation between fetal nasal bone size and gestational age. The variability of nasal bone size became larger as gestational age increased. Minimal length of 1.0 and 4.7 mm in the first and second trimesters, respectively, were found. CONCLUSIONS: there is a direct correlation between fetal nasal bone size and gestational age. This correlation is valid either for a single gestation or a multiple one. These measurements of the fetal nasal bone will allow us to use them as a screening test for cromosomal abnormalities. This is a useful study if we consider the large miscegenation of the Brazilian population. However, further systematic and standardized approach to study the fetal nasal bone is needed to establish its real value in fetuses once classified as at high or low risk for aneuploidies.
