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Cervical lenght as a predictor of preterm delivery in a high risk population
Volume 176, N u m b e r 1, Part 2 A m J Obstet Gynecol
241
SPO Abstracts
U T E R I N E FUNDAL P R E S S U R E - - E N H A N C E D TRANSVAGINAL S O N O GRAPHIC IMAGING OF EARLY SECOND-TRIMESTER FETAL ANATOMY. A. Reichler~, DM. Sherer, M E Divon. Dept. of OB/GYN, Albert Einstein College of Medicine, Bronx, NY. OBJECTIVE: To assess the advantage of applying uterine fundal pressure (FP) to enhance depiction of transvaginal sonographic (TVS) imaging of early second trimester fetal anatomy. M E T H O D S : One hundred consecutive patients with singleton fetuses underwent routine TVS assessment of fetal anatomy between 13 and 17 weeks' gestation. If the entire fetal anatomy including cardiac outflow n-acts was not depicted, FP was applied with the operator's non-scanning hand in a bimanual thshion, to facilitate TVS imaging of fetal structm'es not previously visualized. When visualization was incmnplete with TVS or TVS + FP, a transabdominal scan (TAS) was performed. Observed fetal anatomical structures with and without FP were compared. Confimnding variables assessed included: fetal presentation, patient weight, gestational age, and previous abdominal surgery. Each patient served as her own control. Statistical analysis included Fisher's exact test, X2, and log-likelihood ratio where appropriate with p < 0.05 considered significant. RESULTS: Uterine Ihndal pressure enhanced TVS imaging of fetal anatomy in 91% of the patients, and in 51% of all cases a complete anatonfical survey was obtained. In 20% of all patients a TAS approach was required to complete the sonographic examination. Fetal anatontical scanning was incomplete despite TVS + FP supplemented with TAS in 29% of the cases. Percentages of patients in whom visualization of the various fetal anatomical organs were successfully depicted by the TVS + FP compared to TVS, are noted in the table:
4 ch tracts TVS 28% TVS + FP 74% P value *
10% 62% *
trunk trunk hands 27% 25% 83% 78% 87% 89% * * N8
41% 83% *
31% 86% *
S77
243
I N C O M P E T E N T CERVIX: C H A N G E S W I T H MATERNAL P O S T U R E . G. Wong, .[ Ludmi~; D. Levine', Dept. of Radiology and Ob/Gyn, Berth Israel Hospital, Harvard Medical School, Boston, MA OBJECTIVE: To study the effect of an upright maternal position on the cervix using transt~ginal sonography in patients at risk for incompetent cervix, and to evaluate whether maternal posture can be employed as a functional challenge to predict patients at risk for preterm delivery. STUDY DESIGN: Forty-three patients at risk for incompetent cervix nnderwent transvaginal sonography between 17 to 33 weeks gestations both in the supine position and in an upright position (after standing for 15 minutes). A control population of 24 low risk patients was similarly studied. Pregnancy outcome was evaluated. RESULTS: No change in the cervix was noted in 24 low risk patients after 15 minutes of standing. Mean age of delivery was 39.6 weeks. Of the 43 high risk patients, 15 of 17 who had >33% change in cervical length in the upright position delivered prematurely compared to 2 of 26 patients who had less a than 33% change, with mean gestational age at delivery of 30.2 weeks and 36.7 weeks, respectively" (P < 0.001). The sensitivity and specificiD, of the finding of a >33% posmral change in the cervix to predict premature birth was 88.2% and 92.3%, respectively. When the finding of either a cervical length of <2 cm was combined with a postural change the sensitivity for prediction of preterm delivery was 100%. C O N C L U S I O N S : Changes in maternal posture have no effect on the normal cervix, but can sm~e as a functional test to detect patients at risk for incompetent cepdx and premature deliveW.
244
CAREFUL U L T R A S O U N D FETAL MEASUREMENTS FAIL T O DEMONSTRATE "INTRINSIC" BIOLOGICAL VARIABILITY 1N T H E T H I R D TRIMESTER, ALLOWING A C C U R A T E ESTIMATION OF GESTATIONAL AGE. E. Gurewitscl!,j. Birnholz ~, S. Chasenx, D. Skupski, F. Chervenak. New York Hosp/Cornell Med Ctr, Div. Maternal Fetal Med, New York, NY and Diagnostic Ultrasound Consultants, Oak Brook, IL. OBJECTIVE: A deterioration in accuracy of gestafional dating from standard ultrasound nmasurements has been ascribed m intrinsic biological variability among fetuses as pregnancy progresses. We sought to determine the degree of biologic variability ibund anlong third trimester fetuses when a careful standard of nmasurement is employed. M E T H O D S : Ultrasound measurements of femur length (FL), biparietal diameter (BPD) and occipito-frontal diameter (OFD) were acquired fbr a consecutive series of 2128 clinically normal fetuses in a suburban, predonainantly white, ntiddle class patient population with known date of conception or concordance of ultrasound and menstrual dating prior to 24 weeks' gestation. All Fie measurements were obtained with a 5 MHz, 82 mm linear probe with the femur oriented parallel to the array. BPD and OFD were obtained with the same probe or with a 3.5 MHz sector probe for larger long or short axis nmasurements. A 7 MHz endovaginal probe was used for cranial measurements taken earlier in development. Three or more magnified, hard copy images were cluster averaged to obtain the final measurements and plotted as a function of gestational age. RESULTS: The best-fi t cmwes for FL and shape-corrected BPD measurenmnts yielded the following relationships to gestational age: GA 16.221238 + 26.334746 exp (FL/99.51697) R2 = .997; and GA 18.44199 + 26.173672 exp ( B P D c / l l 9 81981) R2 = .994 There was essentially no data spread for FL through 35 weeks' gestation or for shape-corrected BPD between 15 and 31 weeks' gestation. C O N C L U S I O N : When careful standards are employed, third trimester ultrasound tetal measurements fail to demonstrate "intrinsic" biological variability and can be reliably used for estimation of gestational age in the tfiird trimester.
limbs feet limbs spine 50% 65% 65% 88% 97% 87% * * *
58% 86% *
TVS = transvaginal sonography, FP fundal pressure, * = p < 0.05, NS = not significant, upper trunk includes: stomach, diaphragm, lower trunk includes: bladder, kidneys, and alMominal wall mnbilical cord insertion. Completion of the fetal anatomical survey with TV8 + FP was not related to fetal presentation (P - 0.13) or maternal weight (P = 0.09), yet was related to gestational age (P < 0.02) and previous abdominal surgery (P = 0.02). C O N C L U S I O N : The results of this prospective stud); suggest that FP during early second-trimester TVS evaluation of the fetal anatomy, significantly facilitates high resolution visualization of fetal structures othmavise located beyond the effective range of the transvaginal transducer.
242
CERVICAL L E N G T H AS A P R E D I C T O R OF PRETERM DELIVERY IN A H I G H RISK P O P U L A T I O N . K. Clohelr L. Chan, E.A. Reece. Dept of Ob/Gyn, Tenlple University School of Medicine, Philadelphia, PA. OBJECllVE: The risk of pretetwn delivery (PTD) is increased in the population of noYmal women who are found to have a short cervix by Wanstraginalsonoglvtphy (TVS) during pregnancy (NEJM 1996;334:567-72). This slndy assesses the ~'alue of cervical length (CL) in the prediction of PTD in high risk pregnancies. M E T H O D S : ~Te prospectively performed TVS on pregnant women with risk 1actors for preterm deliveW. CL was nreasured prior to 24 weeks; between 24 and 28 weeks and beyond 28 weeks of gestation. Risk for PTD associated with mean CL at above gestational ages (GA) was determined. We further exantined whether the relative risk for PTD was affected by the absolute mean CL (<20 ram, <25 mm, <30 him, and <40 ram) with CA. PTD was defined as delivery prior to 34-6/7 weeks GA; and term delivery is defined as birth after 35 weeks in this study in view of the low risk for cmnplieations of prematurity. Data were analysed with ANOVA and Chi square analysis. RESULTS: 127 TVS were per~hrmed on 52 patients. 39 women with preexisting risk factors (previous PTD, cerclage, cone biopsy, uterine anomalies, etc.) for preterm deliverv and 13 women who presented with preterm labor symptoms were studied. PTD occured in 14 women (26.9%) and 38 patients (73.1%) delivered at term. CL (Mean -+ S.D.) is reported below: Table 1
<24 weeks
24-28 weeks
2.81 -+ 1.43 3.47 + 0.98
2.06 • 1.53" 3.22 -+ 0.83
<28 weeks [ >28 weeks m
Preternl delivery Term delivery
2.54 + 1.44" 3.36 + 0.91
3.28 +- 0.93 3.29 "2--1.05
The absolute mean CL of <20 toni, <25 mill, <30 mm, and <40 mm did not predict risk for PTD except in the gronp of patients with CL of <25 mm prior to 24 weeks GA (p = 0.042). The Relative risk (RR) of PTD for each CL are listed: Table 2
Rig PTD
<20 mm
<25 mm
I
<30 ram
<40 mm
3.16 2.00 2.63 0.57
0.89 1.71 1.24 2.62
1
<24 weeks 24-28 weeks <28 weeks >28 weeks
2.08 4.34 2.63 1,70
4.31 3.20 3.61 0.77
C O N C L U S I O N : In patients wittl risk factors for preterin delivery, cervical sonography at less than 28 weeks gestation is useful to identify patients who are at increased risk for preterm delivery. Patients with a cervical length less than 25 mm prior to 24 weeks gestation may benefit from stringent management and surveillance.
241
SPO Abstracts
U T E R I N E FUNDAL P R E S S U R E - - E N H A N C E D TRANSVAGINAL S O N O GRAPHIC IMAGING OF EARLY SECOND-TRIMESTER FETAL ANATOMY. A. Reichler~, DM. Sherer, M E Divon. Dept. of OB/GYN, Albert Einstein College of Medicine, Bronx, NY. OBJECTIVE: To assess the advantage of applying uterine fundal pressure (FP) to enhance depiction of transvaginal sonographic (TVS) imaging of early second trimester fetal anatomy. M E T H O D S : One hundred consecutive patients with singleton fetuses underwent routine TVS assessment of fetal anatomy between 13 and 17 weeks' gestation. If the entire fetal anatomy including cardiac outflow n-acts was not depicted, FP was applied with the operator's non-scanning hand in a bimanual thshion, to facilitate TVS imaging of fetal structm'es not previously visualized. When visualization was incmnplete with TVS or TVS + FP, a transabdominal scan (TAS) was performed. Observed fetal anatomical structures with and without FP were compared. Confimnding variables assessed included: fetal presentation, patient weight, gestational age, and previous abdominal surgery. Each patient served as her own control. Statistical analysis included Fisher's exact test, X2, and log-likelihood ratio where appropriate with p < 0.05 considered significant. RESULTS: Uterine Ihndal pressure enhanced TVS imaging of fetal anatomy in 91% of the patients, and in 51% of all cases a complete anatonfical survey was obtained. In 20% of all patients a TAS approach was required to complete the sonographic examination. Fetal anatontical scanning was incomplete despite TVS + FP supplemented with TAS in 29% of the cases. Percentages of patients in whom visualization of the various fetal anatomical organs were successfully depicted by the TVS + FP compared to TVS, are noted in the table:
4 ch tracts TVS 28% TVS + FP 74% P value *
10% 62% *
trunk trunk hands 27% 25% 83% 78% 87% 89% * * N8
41% 83% *
31% 86% *
S77
243
I N C O M P E T E N T CERVIX: C H A N G E S W I T H MATERNAL P O S T U R E . G. Wong, .[ Ludmi~; D. Levine', Dept. of Radiology and Ob/Gyn, Berth Israel Hospital, Harvard Medical School, Boston, MA OBJECTIVE: To study the effect of an upright maternal position on the cervix using transt~ginal sonography in patients at risk for incompetent cervix, and to evaluate whether maternal posture can be employed as a functional challenge to predict patients at risk for preterm delivery. STUDY DESIGN: Forty-three patients at risk for incompetent cervix nnderwent transvaginal sonography between 17 to 33 weeks gestations both in the supine position and in an upright position (after standing for 15 minutes). A control population of 24 low risk patients was similarly studied. Pregnancy outcome was evaluated. RESULTS: No change in the cervix was noted in 24 low risk patients after 15 minutes of standing. Mean age of delivery was 39.6 weeks. Of the 43 high risk patients, 15 of 17 who had >33% change in cervical length in the upright position delivered prematurely compared to 2 of 26 patients who had less a than 33% change, with mean gestational age at delivery of 30.2 weeks and 36.7 weeks, respectively" (P < 0.001). The sensitivity and specificiD, of the finding of a >33% posmral change in the cervix to predict premature birth was 88.2% and 92.3%, respectively. When the finding of either a cervical length of <2 cm was combined with a postural change the sensitivity for prediction of preterm delivery was 100%. C O N C L U S I O N S : Changes in maternal posture have no effect on the normal cervix, but can sm~e as a functional test to detect patients at risk for incompetent cepdx and premature deliveW.
244
CAREFUL U L T R A S O U N D FETAL MEASUREMENTS FAIL T O DEMONSTRATE "INTRINSIC" BIOLOGICAL VARIABILITY 1N T H E T H I R D TRIMESTER, ALLOWING A C C U R A T E ESTIMATION OF GESTATIONAL AGE. E. Gurewitscl!,j. Birnholz ~, S. Chasenx, D. Skupski, F. Chervenak. New York Hosp/Cornell Med Ctr, Div. Maternal Fetal Med, New York, NY and Diagnostic Ultrasound Consultants, Oak Brook, IL. OBJECTIVE: A deterioration in accuracy of gestafional dating from standard ultrasound nmasurements has been ascribed m intrinsic biological variability among fetuses as pregnancy progresses. We sought to determine the degree of biologic variability ibund anlong third trimester fetuses when a careful standard of nmasurement is employed. M E T H O D S : Ultrasound measurements of femur length (FL), biparietal diameter (BPD) and occipito-frontal diameter (OFD) were acquired fbr a consecutive series of 2128 clinically normal fetuses in a suburban, predonainantly white, ntiddle class patient population with known date of conception or concordance of ultrasound and menstrual dating prior to 24 weeks' gestation. All Fie measurements were obtained with a 5 MHz, 82 mm linear probe with the femur oriented parallel to the array. BPD and OFD were obtained with the same probe or with a 3.5 MHz sector probe for larger long or short axis nmasurements. A 7 MHz endovaginal probe was used for cranial measurements taken earlier in development. Three or more magnified, hard copy images were cluster averaged to obtain the final measurements and plotted as a function of gestational age. RESULTS: The best-fi t cmwes for FL and shape-corrected BPD measurenmnts yielded the following relationships to gestational age: GA 16.221238 + 26.334746 exp (FL/99.51697) R2 = .997; and GA 18.44199 + 26.173672 exp ( B P D c / l l 9 81981) R2 = .994 There was essentially no data spread for FL through 35 weeks' gestation or for shape-corrected BPD between 15 and 31 weeks' gestation. C O N C L U S I O N : When careful standards are employed, third trimester ultrasound tetal measurements fail to demonstrate "intrinsic" biological variability and can be reliably used for estimation of gestational age in the tfiird trimester.
limbs feet limbs spine 50% 65% 65% 88% 97% 87% * * *
58% 86% *
TVS = transvaginal sonography, FP fundal pressure, * = p < 0.05, NS = not significant, upper trunk includes: stomach, diaphragm, lower trunk includes: bladder, kidneys, and alMominal wall mnbilical cord insertion. Completion of the fetal anatomical survey with TV8 + FP was not related to fetal presentation (P - 0.13) or maternal weight (P = 0.09), yet was related to gestational age (P < 0.02) and previous abdominal surgery (P = 0.02). C O N C L U S I O N : The results of this prospective stud); suggest that FP during early second-trimester TVS evaluation of the fetal anatomy, significantly facilitates high resolution visualization of fetal structures othmavise located beyond the effective range of the transvaginal transducer.
242
CERVICAL L E N G T H AS A P R E D I C T O R OF PRETERM DELIVERY IN A H I G H RISK P O P U L A T I O N . K. Clohelr L. Chan, E.A. Reece. Dept of Ob/Gyn, Tenlple University School of Medicine, Philadelphia, PA. OBJECllVE: The risk of pretetwn delivery (PTD) is increased in the population of noYmal women who are found to have a short cervix by Wanstraginalsonoglvtphy (TVS) during pregnancy (NEJM 1996;334:567-72). This slndy assesses the ~'alue of cervical length (CL) in the prediction of PTD in high risk pregnancies. M E T H O D S : ~Te prospectively performed TVS on pregnant women with risk 1actors for preterm deliveW. CL was nreasured prior to 24 weeks; between 24 and 28 weeks and beyond 28 weeks of gestation. Risk for PTD associated with mean CL at above gestational ages (GA) was determined. We further exantined whether the relative risk for PTD was affected by the absolute mean CL (<20 ram, <25 mm, <30 him, and <40 ram) with CA. PTD was defined as delivery prior to 34-6/7 weeks GA; and term delivery is defined as birth after 35 weeks in this study in view of the low risk for cmnplieations of prematurity. Data were analysed with ANOVA and Chi square analysis. RESULTS: 127 TVS were per~hrmed on 52 patients. 39 women with preexisting risk factors (previous PTD, cerclage, cone biopsy, uterine anomalies, etc.) for preterm deliverv and 13 women who presented with preterm labor symptoms were studied. PTD occured in 14 women (26.9%) and 38 patients (73.1%) delivered at term. CL (Mean -+ S.D.) is reported below: Table 1
<24 weeks
24-28 weeks
2.81 -+ 1.43 3.47 + 0.98
2.06 • 1.53" 3.22 -+ 0.83
<28 weeks [ >28 weeks m
Preternl delivery Term delivery
2.54 + 1.44" 3.36 + 0.91
3.28 +- 0.93 3.29 "2--1.05
The absolute mean CL of <20 toni, <25 mill, <30 mm, and <40 mm did not predict risk for PTD except in the gronp of patients with CL of <25 mm prior to 24 weeks GA (p = 0.042). The Relative risk (RR) of PTD for each CL are listed: Table 2
Rig PTD
<20 mm
<25 mm
I
<30 ram
<40 mm
3.16 2.00 2.63 0.57
0.89 1.71 1.24 2.62
1
<24 weeks 24-28 weeks <28 weeks >28 weeks
2.08 4.34 2.63 1,70
4.31 3.20 3.61 0.77
C O N C L U S I O N : In patients wittl risk factors for preterin delivery, cervical sonography at less than 28 weeks gestation is useful to identify patients who are at increased risk for preterm delivery. Patients with a cervical length less than 25 mm prior to 24 weeks gestation may benefit from stringent management and surveillance.