Poster Session I Ultrasound, Fetus, Genetics www.AJOG.org

Demographic and outcome data from a universalcervical length screening program

CL cervical length; TVU transvaginal ultrasound; sPTB spontaneous preterm

birth.

*1 woman had CL¼26mm, repeat CL ¼ 11mm.

136

A prospective study of fetal lung maturity tests in twinsbased on birth order and weightDonna Lambers1, Stepanida Freeman1, Michaela Eschenbacher2,Mounira Habli11Trihealth-Good Samaritan Hospital, Obstetrics and Gynecology, Cincinnati,OH, 2Trihealth-Good Samaritan Hospital, Hatton Institute for Research,Cincinnati, OH

OBJECTIVE: To evaluate fetal lung maturity (FLM) tests in twins basedon birth order, birth weight and gender. Our hypothesis is that thesevariables are poor predictors of FLM coorelation within twin pairs.STUDY DESIGN: Prospective cohort of twins was conducted(ClinicalTrials.gov:NCT01385267). During cesarean delivery, amni-otic fluid from each sac of the twins was aspirated, and analyzed forFLM with FLM index and lamellar body count (LBC). Establishedcutoff values for each test were used to classify each infant as mature

S82 American Journal of Obstetrics & Gynecology Supplement to JANUARY 2

or not mature. Pregnancy, delivery and newborn data wereabstracted from the medical records.RESULTS: 49 patients with 98 acceptable amniotic fluid samples wereincluded. Median gestational age at delivery was 36.4 weeks(IQR¼3.3). The only difference in baseline characteristics wasbirthweight of twin A > twin B (2490g v 2356g, p¼0.046). A ROCcurve analysis of FLM tests in twin pregnancy was similar tosingleton maturity threshold values (FLM index > 55mg/g andLBC>29 uL). There was good correlation for the numeric maturityvalues between twins A and B for both tests (FLM index r¼0.73;LBC r¼0.58). There were 17 twin pairs with discordant lungmaturity classifications for both FLM index and LBC. The positivepredictive value (PPV) for twin B predicting twin A’s maturity was83% for FLM index and 62% for LBC. The PPV for the larger twinpredicting the smaller twin’s maturity was 60% for FLM index and83% for LBC. The PPV of male being mature and predicting thefemale co-twin to be mature was 58% for FLM index and 56% forLBC (Table). There was no difference in composite respiratorymorbidity based on birth order, birth weight, or gender. Six infantsclassified as mature by FLM index (4) or LBC (4) experienced res-piratory morbidity.CONCLUSION: For nonindicated/elective delivery of twins, amnio-centesis for FLM should be performed on both amniotic sacs, sincebirth order, birth weight and gender are poor predictors of FLMcorrelation within twin pairs.

Validity of using birth order, birth weight, andgender as predictors of lung maturity

137 Can the gestation-adjusted projection (GAP) method be

used in obese to super morbidly obese women to predict birthweight?Homa Ahmadzia1, Emily Patel1, Huizi Lian2, Samantha Thomas2,Terrence Allen3, Chad Grotegut1, Brita Boyd11Duke University Medical Center, Obstetrics and Gynecology, Durham, NC,2Duke University Medical Center, Biostatistics, Durham, NC, 3DukeUniversity Medical Center, Anesthesiology, Durham, NC

OBJECTIVE: The gestation-adjusted projection (GAP) method usesthird trimester ultrasound fetal weight to predict birth weight (BW).Our study sought to determine if the accuracy of the GAP methoddiffered between obese, morbidly obese and super morbidly obesewomen in predicting BW.STUDY DESIGN: We conducted a retrospective cohort study of allsingleton pregnancies that had a fetal growth assessment between34+0 and 36+6 weeks. A ‘reference’ BMI group (BMI 30-35) wascompared to subcategories of women with a BMI � 40. The absolutegram and percent differences predicted by the GAP method andactual BW were calculated and compared. Chi-square tests andanalysis of variance were used to determine significance.

014

www.AJOG.org Ultrasound, Fetus, Genetics Poster Session I

RESULTS: A total of 429 pregnant women were included, with 208women in the ‘reference’ group. Among women with a BMI � 40,the mean BMI was 51.4 � 8.4 (SD) kg/m2. The GAP method pre-dicted birth weight by � 15% in 86.1% (95% CI 81.6, 90.5) of thesubjects in the ‘reference’ group, which was comparable to the othersubcategories, Table 1.The mean absolute gram and percent differ-ences were not significantly different between the categories, Table 1.In fetuses with an actual BW greater than 4000 grams, the GAPmethod was comparable in predicting BW within � 15% (p¼0.19)among all BMI categories. When tested independently in a logisticregression model, diabetes (p¼0.07), suspected fetal macrosomia/growth restriction (p¼0.25/0.43), race (p¼0.76), chronic hyperten-sion (p¼0.56) oligohydramnios (p¼0.49) and detected anomalieson ultrasound (p¼0.56) did not significantly alter the percentageof predicted BW that fell within � 15% among women with aBMI > 40.CONCLUSION: The GAP method may be used in morbid/supermorbidly obese women with the same degree of accuracy comparedto obese women. Given the limited utility of clinical estimated fetalweights in the morbid/super morbidly obese population, the GAPmethod may be an acceptable alternative to help guide deliveryplanning recommendations.

Using the gestation-adjusted prediction method topredict birth weight in obese to super morbidlyobese women

138 Prediction of birth weight by early versus late third

trimester ultrasound in morbidly obese womenHoma Ahmadzia1, Huizi Lian2, Sarah Moustafa1, Ann Dude1,Jennifer Gilner1, Samantha Thomas2, Terrence Allen3,Chad Grotegut1, Brita Boyd11Duke University Medical Center, Obstetrics and Gynecology, Durham, NC,2Duke University Medical Center, Biostatistics, Durham, NC, 3DukeUniversity Medical Center, Anesthesiology, Durham, NC

OBJECTIVE: To compare the accuracy of predicted birth weight by thegestation-adjusted projection (GAP) method in morbidly obesewomen using early versus late third trimester ultrasound.STUDY DESIGN:We conducted a retrospective cohort study from 2007to 2012 of all singleton pregnancies with a BMI of greater than 40 atthe time of delivery who had both a fetal growth assessment between30+0 and 35+0 weeks (EARLY) and greater than 35+0 weeks(LATE). The absolute gram and percent differences predicted by theGAP method and actual birth weight (BW) were calculated andcompared between the two time periods using paired t tests.RESULTS: A total of 235 obese women were included in this study.The mean (� standard deviation) age was 29.1 � 6.1 years and themean BMI was 50.7 � 7.8 kg/m2. The GAP method predicted actualBW by� 15% in 85.5% cases (95% CI 81.0, 90.0) during the EARLYperiod and in 89.8% cases (95% CI 85.9, 93.7) during the LATEperiod (p¼0.10). The mean absolute difference was 262 � 262grams in EARLY period and 251 � 191 grams in LATE period(p¼0.50). The mean absolute percent difference was also compa-rable in the two periods (EARLY 7.9 � 6.7%, LATE 7.4 � 5.6%;p¼0.33), Figure 1. These findings did not significantly change when

Supplem

examining mean absolute percent differences for fetuses at risk onultrasound for growth restriction (11.1 � 9.0%, 7.2 � 4.5%;p¼0.11) or macrosomia (6.6 � 6.2%, 9.0 � 5.0%; p¼0.08). In fe-tuses with actual BW greater than 4000 grams, the GAP methodequally predicted BW by � 15% in 86.7% of women in both periods(95% CI 82.3, 91.0; p¼1.0).CONCLUSION: Prediction of birth weight using the GAP method inobese women does not appear to be influenced by timing of thirdtrimester ultrasound. The accuracy of the method is not significantlychanged in cases of suspected growth restriction or macrosomia. In apopulation where clinical estimated fetal weight is difficult, the GAPmethod may aid in delivery planning.

139

Estimation of the rate of growth in fetuses with anabnormal cerebroplacental ratio, compared to those withsuspected fetal growth restriction without evidence ofcentralization of blood flowJodi Regan1, Heather Masters1, Carri Warshak11University of Cincinnati College of Medicine, Maternal Fetal Medicine,Cincinnati, OH

OBJECTIVE: Evaluate the rate of growth as measured by serial ultra-sound in fetuses with suspected growth restriction (FGR) in threestudy groups: (1) normal umbilical Doppler evaluation (UA), (2)abnormal UA, but normal cerebroplacental ratio (CPR), and (3)abnormal UA and abnormal CPR.STUDY DESIGN: A retrospective cohort of fetuses with suspected FGRwas identified. We defined FGR as an estimated fetal weight less thanthe 10th percentile and/or an abdominal circumference less than the5th percentile. We reviewed UA and middle cerebral Doppler pul-satility indices, and calculated the CPR (CPR¼MCA PI/ UA PI). Theprimary outcome was the rate of growth in gm/day as estimated bycalculated fetal biometry from serial ultrasound evaluations. Analysisof the mean rate of growth in each study group was performed usingANOVA. In addition, linear regression analysis comparing the CPRto the rate of growth was performed.RESULTS: We identified 227 patients who were diagnosed with FGR.After considering exclusion criteria, 167 patients were included inthis analysis: 111, 25 and 31 in Group 1,2 and 3 respectively. The rateof growth in Group 3 was significantly lower than Groups 1 and 2:8.3 gm/ day versus 19.0 and 17.6 gm/day respectively (p<0.01).Linear regression analysis revealed a strong correlation between therate of growth and the CPR, with a correlation coefficient of 0.82and r squared value of 0.67.

ent to JANUARY 2014 American Journal of Obstetrics & Gynecology S83