182

350 SPO Abstracts

THE USE OF SECOND TRIMESTER FETAL GROWTH CURVES IN PREDICTING INTRAUTERINE GROWTH RETARDATION IN CASES OF UNEXPLAINED MATERNAL SERUM ALPHA FETOPROTEIN ELEVATIONS. ~ A. Vintzileos, J. Rodis, M. McMahon.x Univ. of Connecticut Hea~h Center, Farmington, CT. OBJECTIVE: To assass the abi~y of second trimester fetal growth curves to predict intrauterine growth retardation (IUGR) in cases of unexplained elevated maternal serum alpha fetoprotein (MSAFP). STUDY DESIGN: A retrospective analysis was performed on singleton pregnancies with a single second trimester elevated MSAFP <! 2.0 mu~iples of the median (MOM). Patients wereeligible ff a targeted u~rasound evaluation ($24 weeks) was in agreement with dates with no detectable fetoplacental anomaly. Estimated fetal weight (EFW) was calculated using Hadlock's formulas (BPDlAC and FUAC). The EFW obtained on the in~ial second trimester scan was stratlied into percentiles (%ile) using second trimester growth curves established at our institution. Delw8lY data were obtained from the delivering physician. IUGR was defined as a birthweight <lOth %iIe. RESULTS: Of 337 patients enrolled, deivery data were avaiable on 303 infants. 35 nonanomalous, IUGR infants were delivered between 23 and 42 weeks gestation. The sens~iv~y (SENS), specffic~ (SPEC), pos~iveand negative predictive values (PPV,NPV) were determined for second trimester growth curves using EFW cut-offs of <10th and <50th %ie and MSAFP elevations <!2.0 and <!2.5 MOM.

~.O '-«)M (n=303) ~.5 MOM (I1=t36) < 10th %ile < 50th %ile < 10th %ile < 50fI %ile

EFW BPOIAC FUAC BPOIAC FUAC BPOIAC FUAC BPOIAC FUAC SENS 17.1 17.1 771 77.1 19.1 19.1 71.4 76.2 SPEC 97.8 98.5 63.1 60.8 99.1 100.0 60.9 61.7 PPV SO.O 60.0 21.4 20.5 60.0 100.0 25.0 26.7 N PV 90.0 90.1 95.5 95.3 87.0 87.1 92.1 93.4

(prevalence oflUGR 11.5%) (prevalence of IUGR 15.4%)

CONCLUSION: Second trimester growth curves can assist the clinician in discriminating between pregnancies at high risk fOf subsequent IUGR (PPV of EFW <10th %ile, so. 1000/0) and in roeed of seriallJlS fOf growth, and those at low risk fOf MurelUGR (NPV of EFW <50th %ite, 93-95%) not requiring such intervention.

183 NIIIOCEITESIS All) TAR6£TED II.TR.UOII06RAPHY II THE EYALlUITlDI Of REYATED IMTEItIIAL SEIIII AFP (IISAFP). ~,J. Maher, M. DuBard, C. Br ... fleld, J . Owen, l. Boots', and P. Cosper'. Dept . of Obstetrics/Gynecology , Laboratory of Medical Genetics, University of Alabama at Birmingham, Birmingham, AL. OBJECTIVE: To examl ne the trend I n the use of targeted sonography subsequent to amniocentesis to identify neural tube and abdomi na 1 wall defects I n the presence of an elevated MSAFP. STUDT DE51611: A total of 701 women were referred from 1986-1990 for evaluation of an elevated I4SAFP (>2 140M) . Prenatal detection of fetal an"",,,lies by ultrasound exam or amniocentesis was detemined . Pregnancy outcomes were confirmed In 528 patients either by contacting the referring physicians' office or the patient directly. RESULTS: There were 668 singleton and 33 twin pregnancies. All underwent a targeted ultrasound examination and were offered amniocentesis . Overall, 334 (49 . 9%) singleton pregnancies, underwent an amniocentesis while 6 (16 . 7%) twin pregnancies underwent amniocentesis . In singleton pregnancies , the rate of amniocentesis decreased from 82 . 2% in 1986 to 25 . 5% in 1990 (p<.OOI) . lInder this management protocol, 33 neural tube defects and 5 abdominal wall defects were identified prenatally by ultrasound. No additional structural anomalies were identified by amniocentesis. One aneupl 01 d pregnancy was di agnosed, 46,XX/47XX,+20, which subsequently del ivered a normal baby at term. No undiagnosed neural tube or abdomi na 1 wall defect was reported to us by referring physiCians or by any patient. CDlCLUSIDl: The use of amniocentesis in the evaluation of an elevated MSAFP fell about 3-fold from 1986-1990 without missing any abdominal wall or neural tube defect. This decrease in amniocentesis rate Is most likely explained by increased confidence In the targeted ultrasound examination to rule out the presence of a fetal neural tube or abdomi na 1 wall defect.

184

January 1993 Am J Obstet Gynecol

AMNIOTIC FLUID VOLUME: A MAJOR DETERMINANT OF FETAL VISUALIZATION. HM Wolfe, MP Dombrowski, IE Zaoot, Me Treadwell, RJ Sokol, Dept. of OBIGYN, Hutzel Hosp., Wayne State Univ., D<troit MI.

OBJECTIVE: Amniotic fluid volume (AFV) abnonnalities are associated with fctal structural and chromosomal anomalies, making thorough evaluation of fctal anatomy ...... tial . Our goal wall to delineate the effect of AFV on fctal visualization.

STUDY DESIGN: We examined 2911 pregnancies at > 14 weeks. AFV wall grouped by amniotic fluid index and/or visual appearance as nonnal, polyhydramnios (poly), increased (incr), oligohydramnios (oligo) or decreased (decr) . Multivariate analysis for organ visualization and overall visualization was perfonned.

RESULTS: As a quasi-oontinuous variable, Al'V was significantly associated (p < 0 .02) with overall visualization, second only to maternal weight in d<tennining visualization, having a greater impact than gestational age. With oligo and decr AFV, overall visualization decreased by 24 and 8 %; extremities and umbilical cord were most affected with minimal change for kidneys. Incr fluid and poly improved visualization mainly for fetal heart.

PERCENT VISUALIZATION

Heart Kidneys Stomach Bladder ExtremitiES Umbilical Cord OVERALL

Oligo Deer Nonnal 42 SS 5S 91 92 95 89 99 89 93 98 99 14 54 81 27 68 80 66 81 87

lnu 76 98

100 99 86 95 93

Poly 86

100 100 100 87

100 9S

CONCLUSIONS: The full range of AFV has a major, linear impact on fetal visualization . This effect, however, is highly organ specific. When considering amnioinfusion, the clinician shoutd critically evaluate the likelihood of imprOVed visualization for structures of interest.

185 OPTIMAL GESTATIONAl AGES FOR THE VISUALIZATION OF ANATOMIC STRUCTURES IN THE NORMAL FETUS. Kirk JS, Comstock CH, Lee W. Division of Fetal Imaging, Dept. OB·GYN, William Beaumont Hosp~aI, Royal Oak, MI. OBJECTIVE: The hypothesis Is that there are optimal gestational ages when different structures can be visualized In the normal fetus. STUDY DESIGN: All transabdominal scans performed at 10 to 41 weeks In our un~ from 12/10/90 to 6/27/92 were analyzed. Equipment Included the Acuson 128, Acuson 128 XP/l0, Aloka 650, and Philips Platinum systems. Only patients w~h normal fetuses who delivered at our hosp~al were Included. If muHlple scans were performed during a pregnancy, one scan was chosen randomly to include In the study. The study consisted of 3,772 scans. The percentage of scans in which Individual anatomic structures were visualized was determined for each week of gestation. RESULTS: Below are the gestational ages when anatomic structures could be visualized in >90% of scans. structure - weeks structure ~ cerebral ventricles 15-41 cisterna magna 15-30 spine 16-28 face 2O~ heart, 4 chambers 17-31 heart, 5 chambers 20-23 stomach 13-41 ventral wall 14-28 kidneys 15-41 bladder 1441 extrem~ies 14-26 cord vessels 17-29 CONCUJSIONS: The optimal time when the highest percentage of all structures could be visualized was 19-28 weeks. Our resuHs show improved visualization as compared to an earlier study performed throughout gestation (JUM 7:197-201, 1988) and provides additional intormation regarding the cisterna magna, face, and 5 chamber view of the heart. By establishing standards in our un~, we have a basis of comparison for ourselves and for the evaluation of equipment. The informatiOn also provides referring physicians with guidelines for ordering prenatal scans in a timely manner.