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The pattern of discordant fetal growth according to chorionicity
SMFM Abstracts S231
Volume 189, Number 6 Am J Obstet Gynecol 631
MAGNETIC RESONANCE LUNG VOLUMES IN FETUSES WITH SUSPECTED GENITOURINARY ABNORMALITIES M. ZARETSKY1, R. RAMUS1, D. MCINTIRE1, K. MAGEE1, D.M. TWICKLER2, 1University of Texas Southwestern Medical Center, OB/GYN, Dallas, TX 2University of Texas Southwestern Medical Center, Radiology, Dallas, TX OBJECTIVES: To determine magnetic resonance (MR) total lung volumes (TLV) in fetuses with suspected genitourinary (GU) abnormalities and assess their correlation with lethal pulmonary hypoplasia. STUDY DESIGN: Fetuses with suspected GU abnormalities underwent blinded retrospective calculation of TLV by outlining regions of interest on consecutive axial MR slices, with slice thickness varying between 4 mm and 7 mm from a superfast MR protocol. Lethal and non-lethal groups were assigned based on neonatal outcomes. A TLV/gestational age (GA) ratio was determined for each fetus. Distribution of the TLV/GA ratios for both groups was compared using the Wilcoxon rank sum test, and the slopes of the TLV by GA were compared with analysis of covariance. RESULTS: Of 45 MR studies in the GU database, there were 21 lethal and 24 non-lethal outcomes. GA at time of TLV calculation ranged from 17 to 38 weeks. There is a significant difference between the TLV/GA ratios of the lethal and non-lethal groups (P = .0001). The slopes of the lethal and non-lethal groups are significantly different (P = .005). However, it is not until 26 weeks that there is separation of the 95% confidence intervals. The median values for the TLV/ GA ratio for lethal and non-lethal GU groups are 0.51 and 1.48, respectively.
633
THE PATTERN OF DISCORDANT FETAL GROWTH ACCORDING TO CHORIONICITY STEPHANIE KLAM1, LARISSA TAKSER1, DENYSE RINFRET1, LINE LEDUC1, 1Hopital Ste-Justine, Maternal-Fetal-Medicine, Montreal, Quebec, Canada OBJECTIVE: To evaluate the effect of chorionicity on the pattern of discordant fetal growth in a large cohort of monochorionic (MC) and dichorionic (DC) twin pairs. STUDY DESIGN: A prospective cohort encompassing all cases of prenatally diagnosed twin gestations followed through to delivery from 1997 to 2002. Serial ultrasound examinations were performed at 2- to 4-week intervals. Chorionicity was determined by standard sonographic criteria in early pregnancy. The estimated fetal weight (EFW) was obtained from Arbuckle tables using abdominal circumference and femur length measurements. Discordance was determined by dividing the difference between the EFWs of the twins by the EFW of the larger twin (3100%). The direction and rate of change of discordance as a continuous variable was estimated for both MC and DC twin pairs using SAS MIXED procedure for repeated measures. A variance-covariance structure was modeled prior to fixed effect estimating. The interaction between gestational age and chorionicity was also tested. RESULTS: 503 consecutive twin pairs were studied, excluding all cases of twin-twin transfusion and monoamniotic twin pregnancies. Analysis was based on 1839 ultrasound exams performed after 19 weeks’ gestation. Actual twin birth weight discordance of 25% or greater was present in 19% (24/125) of MC and 11.5% (43/378) of DC twins. Although the pattern of discordance was the same for both MC and DC twin pairs, the gestational age at onset was earlier in MC twins. Fetal weight discrepancy increased throughout gestation in both MC and DC twins (0.1% per week, P = 0.02); however, a significant difference (P < 0.0001) was observed for intercept value between MC and DC twins (the linear equation for MC twins was estimated at 10% ± 0.1% per week versus 4% ± 0.1% per week in DC twins). The interaction between gestational age and chorionicity was not significant. CONCLUSION: Discordance in MC twins tends to occur earlier in gestation and remains increased at a 6% faster rate throughout gestation, as compared to DC twins.
634
MR EVALUATION OF SUSPECTED ACUTE APPENDICITIS IN PREGNANCY AIMEE D. EYVAZZADEH1, IVAN PEDROSA2, JODI ABBOTT1, NEIL M. ROFSKY2, DEBORAH LEVINE2, 1Beth Israel Deaconess Medical Center, Department of Obstetrics and Gynecology, Boston, MA 2Beth Israel Deaconess Medical Center, Department of Radiology, Boston, MA OBJECTIVE: To evaluate the diagnostic value of MR imaging in pregnant patients with clinical suspicion of acute appendicitis. STUDY DESIGN: MR imaging was performed in 25 pregnant patients (mean maternal age 28 y.o., range 19-39; mean gestational age 18 weeks, range 436 weeks) with clinical suspicion of acute appendicitis. 23 patients had abdominal ultrasound (US) examinations. MR imaging was performed one hour after administration of oral contrast. Three radiologists retrospectively reviewed all MR examinations and results were given by consensus. MR images were reviewed for the presence of an enlarged appendix (more than 6 mm in diameter), fluid-filled appendix, peri-appendiceal inflammatory changes, phlegmon, or abscess. The presence of additional abnormal findings in the abdomen/pelvis was also tabulated. RESULTS: MR sensitivity and specificity for the diagnosis of acute appendicitis was 100%. One patient had acute appendicitis on MR and US examinations. Twenty-four patients had no acute appendicitis based on imaging studies and clinical follow-up. The normal appendix was visualized in 2 (9%) patients with US and 22 (91.7%) patients with MR imaging (P < 0.01). The average diameter of the normal appendix was 5.3 mm ± 0.9 mm. Alternative MR findings related to presented symptoms included uterine fibroids with cystic degeneration (n = 3), moderate right-sided hydronephrosis (n = 8), subchorionic hemorrhage (n = 7), enlarged right ovary secondary to torsion (n = 1), enlarged right venous varices (n = 2), and air within the urinary bladder due to enterococcus infection (n = 1). CONCLUSION: MR imaging visualizes the normal appendix in a high percentage of pregnant patients with suspected acute appendicitis. MR is valuable for the diagnosis of acute appendicitis in patients with a non-diagnostic US examination and can provide alternative diagnoses in a substantial number of pregnant patients.
CONCLUSION: There is a significant difference between TLV/GA ratios in the lethal and non-lethal GU abnormality groups. Prior to 26 weeks, however, there is no recognizable difference between lethal and non-lethal TLV.
632
ABDOMINAL CIRCUMFERENCE RATIO: A USEFUL PREDICTOR OF TWIN BIRTH WEIGHT DISCORDANCE STEPHANIE KLAM1, DENYSE RINFRET1, LINE LEDUC1, 1Hopital Ste-Justine, Maternal-Fetal-Medicine, Montreal, Quebec, Canada OBJECTIVES: To assess the accuracy of sonographic prediction of twin birth weight discordance using the abdominal circumference (AC) ratio. Additionally, to determine whether the efficacy of this method is dependent on chorionicity. STUDY DESIGN: A prospective cohort encompassing all cases of prenatally diagnosed twin gestations followed through to delivery from 1997 to 2002. Serial ultrasound examinations were performed every 2-4 weeks (range: 11.1 to 38.4 weeks’ gestation). The AC ratio was obtained by dividing the AC of the smaller twin by the AC of the larger twin. Twin birthweight discordance was calculated by dividing the difference between the weight of the twins by the weight of the larger twin, expressed as a percentage. The sensitivity, specificity, and predictive values of the AC ratio were assessed for the prediction of growth discordance in monochorionic (MC) and dichorionic (DC) twin pregnancies. RESULTS: 503 consecutive twin deliveries were studied, excluding all cases of twin-twin transfusion and monoamniotic twin pregnancies. 2224 ultrasound examinations were performed on 378 DC and 125 MC twin pairs (average 4.4 ± 1.4 exams per pregnancy). The AC ratio could be measured consistently throughout gestation in 100% of twin pairs. 19.2% (24/125) of MC and 11.5% (43/378) of DC twin pairs exhibited discordant growth, defined as a birthweight disparity of 25% or greater. Sonographic prediction of birthweight discordance using AC ratio < 0.93 had an overall sensitivity of 61%, specificity of 84%, PPV of 40%, and NPV of 93%. CONCLUSION: The AC ratio is a simple and reliable measurement that can be obtained throughout gestation with comparable efficacy to other thirdtrimester growth parameters for predicting fetal growth discordance. Furthermore, the reliability in estimating inter-twin birthweight discordance in MC twins is superior.
MC DC
#U/S Exams
Sensitiv.
Specific.
PPV
NPV
636 1588
80% 48%
73% 88%
45% 35%
93% 92%
Volume 189, Number 6 Am J Obstet Gynecol 631
MAGNETIC RESONANCE LUNG VOLUMES IN FETUSES WITH SUSPECTED GENITOURINARY ABNORMALITIES M. ZARETSKY1, R. RAMUS1, D. MCINTIRE1, K. MAGEE1, D.M. TWICKLER2, 1University of Texas Southwestern Medical Center, OB/GYN, Dallas, TX 2University of Texas Southwestern Medical Center, Radiology, Dallas, TX OBJECTIVES: To determine magnetic resonance (MR) total lung volumes (TLV) in fetuses with suspected genitourinary (GU) abnormalities and assess their correlation with lethal pulmonary hypoplasia. STUDY DESIGN: Fetuses with suspected GU abnormalities underwent blinded retrospective calculation of TLV by outlining regions of interest on consecutive axial MR slices, with slice thickness varying between 4 mm and 7 mm from a superfast MR protocol. Lethal and non-lethal groups were assigned based on neonatal outcomes. A TLV/gestational age (GA) ratio was determined for each fetus. Distribution of the TLV/GA ratios for both groups was compared using the Wilcoxon rank sum test, and the slopes of the TLV by GA were compared with analysis of covariance. RESULTS: Of 45 MR studies in the GU database, there were 21 lethal and 24 non-lethal outcomes. GA at time of TLV calculation ranged from 17 to 38 weeks. There is a significant difference between the TLV/GA ratios of the lethal and non-lethal groups (P = .0001). The slopes of the lethal and non-lethal groups are significantly different (P = .005). However, it is not until 26 weeks that there is separation of the 95% confidence intervals. The median values for the TLV/ GA ratio for lethal and non-lethal GU groups are 0.51 and 1.48, respectively.
633
THE PATTERN OF DISCORDANT FETAL GROWTH ACCORDING TO CHORIONICITY STEPHANIE KLAM1, LARISSA TAKSER1, DENYSE RINFRET1, LINE LEDUC1, 1Hopital Ste-Justine, Maternal-Fetal-Medicine, Montreal, Quebec, Canada OBJECTIVE: To evaluate the effect of chorionicity on the pattern of discordant fetal growth in a large cohort of monochorionic (MC) and dichorionic (DC) twin pairs. STUDY DESIGN: A prospective cohort encompassing all cases of prenatally diagnosed twin gestations followed through to delivery from 1997 to 2002. Serial ultrasound examinations were performed at 2- to 4-week intervals. Chorionicity was determined by standard sonographic criteria in early pregnancy. The estimated fetal weight (EFW) was obtained from Arbuckle tables using abdominal circumference and femur length measurements. Discordance was determined by dividing the difference between the EFWs of the twins by the EFW of the larger twin (3100%). The direction and rate of change of discordance as a continuous variable was estimated for both MC and DC twin pairs using SAS MIXED procedure for repeated measures. A variance-covariance structure was modeled prior to fixed effect estimating. The interaction between gestational age and chorionicity was also tested. RESULTS: 503 consecutive twin pairs were studied, excluding all cases of twin-twin transfusion and monoamniotic twin pregnancies. Analysis was based on 1839 ultrasound exams performed after 19 weeks’ gestation. Actual twin birth weight discordance of 25% or greater was present in 19% (24/125) of MC and 11.5% (43/378) of DC twins. Although the pattern of discordance was the same for both MC and DC twin pairs, the gestational age at onset was earlier in MC twins. Fetal weight discrepancy increased throughout gestation in both MC and DC twins (0.1% per week, P = 0.02); however, a significant difference (P < 0.0001) was observed for intercept value between MC and DC twins (the linear equation for MC twins was estimated at 10% ± 0.1% per week versus 4% ± 0.1% per week in DC twins). The interaction between gestational age and chorionicity was not significant. CONCLUSION: Discordance in MC twins tends to occur earlier in gestation and remains increased at a 6% faster rate throughout gestation, as compared to DC twins.
634
MR EVALUATION OF SUSPECTED ACUTE APPENDICITIS IN PREGNANCY AIMEE D. EYVAZZADEH1, IVAN PEDROSA2, JODI ABBOTT1, NEIL M. ROFSKY2, DEBORAH LEVINE2, 1Beth Israel Deaconess Medical Center, Department of Obstetrics and Gynecology, Boston, MA 2Beth Israel Deaconess Medical Center, Department of Radiology, Boston, MA OBJECTIVE: To evaluate the diagnostic value of MR imaging in pregnant patients with clinical suspicion of acute appendicitis. STUDY DESIGN: MR imaging was performed in 25 pregnant patients (mean maternal age 28 y.o., range 19-39; mean gestational age 18 weeks, range 436 weeks) with clinical suspicion of acute appendicitis. 23 patients had abdominal ultrasound (US) examinations. MR imaging was performed one hour after administration of oral contrast. Three radiologists retrospectively reviewed all MR examinations and results were given by consensus. MR images were reviewed for the presence of an enlarged appendix (more than 6 mm in diameter), fluid-filled appendix, peri-appendiceal inflammatory changes, phlegmon, or abscess. The presence of additional abnormal findings in the abdomen/pelvis was also tabulated. RESULTS: MR sensitivity and specificity for the diagnosis of acute appendicitis was 100%. One patient had acute appendicitis on MR and US examinations. Twenty-four patients had no acute appendicitis based on imaging studies and clinical follow-up. The normal appendix was visualized in 2 (9%) patients with US and 22 (91.7%) patients with MR imaging (P < 0.01). The average diameter of the normal appendix was 5.3 mm ± 0.9 mm. Alternative MR findings related to presented symptoms included uterine fibroids with cystic degeneration (n = 3), moderate right-sided hydronephrosis (n = 8), subchorionic hemorrhage (n = 7), enlarged right ovary secondary to torsion (n = 1), enlarged right venous varices (n = 2), and air within the urinary bladder due to enterococcus infection (n = 1). CONCLUSION: MR imaging visualizes the normal appendix in a high percentage of pregnant patients with suspected acute appendicitis. MR is valuable for the diagnosis of acute appendicitis in patients with a non-diagnostic US examination and can provide alternative diagnoses in a substantial number of pregnant patients.
CONCLUSION: There is a significant difference between TLV/GA ratios in the lethal and non-lethal GU abnormality groups. Prior to 26 weeks, however, there is no recognizable difference between lethal and non-lethal TLV.
632
ABDOMINAL CIRCUMFERENCE RATIO: A USEFUL PREDICTOR OF TWIN BIRTH WEIGHT DISCORDANCE STEPHANIE KLAM1, DENYSE RINFRET1, LINE LEDUC1, 1Hopital Ste-Justine, Maternal-Fetal-Medicine, Montreal, Quebec, Canada OBJECTIVES: To assess the accuracy of sonographic prediction of twin birth weight discordance using the abdominal circumference (AC) ratio. Additionally, to determine whether the efficacy of this method is dependent on chorionicity. STUDY DESIGN: A prospective cohort encompassing all cases of prenatally diagnosed twin gestations followed through to delivery from 1997 to 2002. Serial ultrasound examinations were performed every 2-4 weeks (range: 11.1 to 38.4 weeks’ gestation). The AC ratio was obtained by dividing the AC of the smaller twin by the AC of the larger twin. Twin birthweight discordance was calculated by dividing the difference between the weight of the twins by the weight of the larger twin, expressed as a percentage. The sensitivity, specificity, and predictive values of the AC ratio were assessed for the prediction of growth discordance in monochorionic (MC) and dichorionic (DC) twin pregnancies. RESULTS: 503 consecutive twin deliveries were studied, excluding all cases of twin-twin transfusion and monoamniotic twin pregnancies. 2224 ultrasound examinations were performed on 378 DC and 125 MC twin pairs (average 4.4 ± 1.4 exams per pregnancy). The AC ratio could be measured consistently throughout gestation in 100% of twin pairs. 19.2% (24/125) of MC and 11.5% (43/378) of DC twin pairs exhibited discordant growth, defined as a birthweight disparity of 25% or greater. Sonographic prediction of birthweight discordance using AC ratio < 0.93 had an overall sensitivity of 61%, specificity of 84%, PPV of 40%, and NPV of 93%. CONCLUSION: The AC ratio is a simple and reliable measurement that can be obtained throughout gestation with comparable efficacy to other thirdtrimester growth parameters for predicting fetal growth discordance. Furthermore, the reliability in estimating inter-twin birthweight discordance in MC twins is superior.
MC DC
#U/S Exams
Sensitiv.
Specific.
PPV
NPV
636 1588
80% 48%
73% 88%
45% 35%
93% 92%