Volume 158 Number 2

suring cardiac output or in complicated cardiac disease in which accurate diagnosis can be completed only by pulsed Doppler echocardiography examination.

REFERENCES

l. Huhta JC, Strasburger JF, Carpenter RJ, Reiter A, Abi­nader E. Pulsed Doppler fetal echocardiography. J Clin Ultrasound 1985;13:247.

2. Kleinman CS, Donnerstein RL. Ultrasonic assessment of cardiac function in the intact human fetus. J Am Coli Cardiol 1985;5:84S.

3. Maulik D, Nanda NC, Saini VD. Fetal Doppler echocar­diography. Methods and characterization of normal and abnormal hemodynamics. Am J Cardiol 1984;53:572.

4. Queenan JT, in discussion, Maulik D, Nanda NC, Mood­ley S, Saini VD, Thiede HA. Application of Doppler echo­cardiography in the assessment of fetal cardiac disease. AMJ 0BSTET GYNECOL 1985;151:951.

5. Silverman NH, Golbus MS. Echocardiographic tech­niques for assessing normal and abnormal fetal cardiac anatomy. J Am Coli Cardiol 1985;5:205.

6. Allan LD, Crawford DC, Handerson RH, Tynan MJ. Spectrum of congenital heart disease detected echocar­diographically in prenatal life. Br Heart J 1985;54:523.

7. Waldimiroff JW, Vosters R, McGhie JS. Normal cardiac ventricular geometry and function during the last trimes­ter of pregnancy and early neonatal period. Br J Obstet Gynecol 1982;89:839.

Fetal Doppler echocardiography

8. Devore GR, Donnerstein RL, Kleinman CS, Platt LD, HobbinsJC. Fetal echocardiography-1: normal anatomy as determined by real time directed M-mode ultrasound. AMJ 0BSTET GYNECOL 1982;144:249.

9. Allen LD, Crawford DC, Handerson RH, Tynan MJ. Echocardiographic and anatomical correlations in fetal congenital heart disease. Br Heart J 1984;52:542.

10. Waldimiroff JW, McGhie JS. Ultrasonic assessment of car­diovascular geometry and function in the human fetus. Br J Obstet Gynecol 1981;83:870.

11. Devore GR. The prenatal diagnosis of congenital heart disease-a practical approach for the fetal sonographer. J Clin Ultrasound 1985;13:229.

12. Jeanty P, Romero R, Hobbins JC. Fetal pericardia) fluid: a normal finding of the second half of pregnancy. AM J 0BSTET GYNECOL 1984;149:529.

13. Yagel S, Hurwitz A. Pericardia) effusion in the second trimester-a normal finding [Letter]. AM J 0BSTET Gv­NECOL 1985; 152:721.

14. Cuntheroth WG, Kawabori I, Baum D. Tetralogy ofFal­lot. In: Adams FH, Emmanouilides GC, eds. Heart disease in infants, children and adolescents. Baltimore: Williams & Wilkins, 1983:215-28.

15. Emmanouilides GC, Baylen BC. Congenital absence of the pulmonary valve. In: Adams FH, Emmanouilides GC, eds. Heart disease in infants, children and adolescents. Baltimore: Williams & Wilkins, 1983:228-34.

Pulmonary hypoplasia testing in clinical obstetrics

Carl Nimrod, MB, Stuart Nicholson, MD, Dawn Davies, RDMS, Joyce Harder, MD, Gail Dodd, RN, and Reg Sauve, MD

Calgary, Alberta, Canada

An ultrasound-based diagnostic test for predicting pulmonary hypoplasia antenatally by measurements of

fetal chest circumference was applied prospectively to 45 patients at risk for developing this disorder. The

outcome for the newborn infant and the autopsy findings were correlated with the antenatal prediction. The

results of this test demonstrated a sensitivity and a specificity of 88% and 96%, respectively. The

application of this test to clinical practice is recommended. (AM J OBSTET GvNECOL 1988;158:277-80.)

Key words: Pulmonary hypoplasia, chest circumference, ultrasound prediction

Fetal pulmonary hypoplasia is commonly associated with chronic amniotic fluid leakage' and fetal renal dis­ease! The extent of fetal pulmonary hypoplasia de-

From the Departments of Obstetrics, Pediatrics, and Diagnostic Radiology, Faculty of Medicine, University of Calgary Medical School.

Presented at the Forty-third Annual Meeting of The Society of Ob­stetricians and Gynaecologists of Canada, Ottawa, Ontario, Can­ada, June 24-27, 1987.

Reprint requests: Dr. Carl Nimrod, c/o Division of Maternal-Fetal Medicine, University of Calgary, Foothills Hospital, 1403-29th St. N.W., Calgary, Alberta, Canada T2N 2T9.

pends on the degree of oligohydramnios, its duration, and the gestational age and stage of lung development when the oligohydramnios occurred. 3 A spectrum of hypoplasia can therefore be expected, but it is useful clinically to consider the hypoplasia as either lethal or nonlethal.

If this prediction is made antenatally, adequate coun­seling of the mother and appropriate management can take place. A normogram for chest circumferences with advancing gestation has been developed! This nor­mogram was anticipated to be a useful tool for the ante­natal prediction of pulmonary hypoplasia. This study

277

278 Nimrod et al.

Table I. Amniotic flow volume

Ultrasound Oligohydramnios type (No.)

1 16 14 2 2 6 3 3 3 23 10 6

Table II. Summary of Cases I to 6

Mean birth weight (gm)

0 1293 ± 618 0 1582 ± 921 7 1837 ± 843

Gestational age (wk)

30.9 ± 3.3 31.2 ± 5.0 31.9 ± 3.6

February 1988 Am J Obstet Gynecol

Mortality rate (%)

87.5 16.6 13.0

Total duration Duration of Gestational Birth weight Duration of assisted of oxygen Ventilated pressure hospitalization

Case No. age (wk) (gm) ventilation (days)

32 1740 32

2 24 630 59

3 28 970 9

4 39 3260

5 33 1240 2

6 33 1650 0

also prospectively assessed the antenatal prediction of lethal and nonlethal pulmonary hypoplasia in a patient population at risk for developing the disease, which was determined by ultrasound technique.

Material and methods

Patients recruited for the study were attending the Ultrasound Department of Foothills Hospital, a tertiary referral center for high-risk obstetric patients in south­ern Alberta. The inclusion criteria allowed for the re­cruitment of patients with premature rupture of the membranes before 30 weeks' gestation, the appearance of oligohydramnios before 34 weeks' gestation, pleural effusion, or any other condition potentially restricting lung growth. All patients underwent a comprehensive fetal scan, and several other parameters were recorded in detail. ·

Serial quantitation of the amount of amniotic fluid and classification into normal, reduced, or oligohy­dramnios was based on a semiquantitative method of overall assessment of fluid volume followed by mea­surement of the depth of the largest pocket. Measure­ment of <20 mm was considered as indicative of the

(days) (inspired/ expired) (days) Complications

39

102

25

2

0

32/8 45 Pneumothorax, respiratory dis-tress syndrome

24/5 113 Atelectasis, acido-sis, airway ob-struction, em-physema, bron-chopulmonary dysplasia

20/5 77 Atelectasis, em-physema, pneumothorax

Died I hr Pulmonary hypo-plasia, Meckel-Gruber syndrome

18/4 70 Mild respira-tory distress syndrome

0 10 Mild respira-tory distress syndrome

presence of oligohydramnios, and measurements be­tween 20 and 30 mm were classified as reduced fluid volume.

The cephalic index was determined by the method of Hadlock et aP to assess whether dolichocephaly was present. It was felt that this deformation may have a strong correlation with decreases in amniotic fluid.

Chest circumference measurements were made ac­cording to the method of Nimrod et aP This mea­surement, involving a cross section of the fetal chest at right angles to the fetal spine at the atrioventricular valves and demonstrating all chambers of the heart, was taken during episodes of absent fetal breathing. .Hard copies were made, and circumference measure­ments were made off-line with an IBM PC Microsonics package. All measurements were made by one observer. The coefficient of variation previously established for this technique by two observations on each patient was found to be <2% in 15 patients over a 20-week range of gestational age.

Patients were reviewed by ultrasound biweekly if they had not been delivered. For the purposes of the anal­ysis, only the final chest measurement was used. This

Volume 158 Number 2

e

35.0

33.0

31.0

..g 29.0 w ~ 27.0 w ffi 25.0 u.. ::E a 23.0 a: 0 1-(/) w J: 0

Pulmonary hypoplasia testing 279

50th

5th

0

0 0

24.0 26.0 28.0 30.0 32.0 34.0 36.0 38.0 40.0 42.0

WEEKS OF GESTATION

Fig. 1. Chest circumference normogram showing gestational age distribution of fetuses in the bor­derline type (type I) (solid circles) and below the fifth percentile type 2 (open circles). One fetus without pulmonary hypoplasia is shown (boxed open circles).

chest circumference information was not made avail­able to the clinician for management. The chest mea­surements were classified into three types for analysis: (I) patients who had chest circumference measure­ments below the fifth percentile for the gestational age, (2) patients who were at the fifth percentile, and (3) patients who were in the normal range of chest measurement.

Autopsies were done on all newborn infants that died. All babies who were admitted to the neonatal intensive care unit and who required prolonged hos­pitalization were evaluated retrospectively by one of us to assess the nature of respiratory morbidity. The eval­uator did not know the antenatal categorization of the patient. Pulmonary hypoplasia was defined as lung weight below 2 SD for gestational age with lung weight/body weight ratios below 2 SD.

Outcomes of patients, including the mode of deliv­ery, were correlated with the antenatal prediction.

Results Forty-five patients were enrolled in the study over an

IS-month period. Thirty-seven of these patients (82%) had preterm premature rupture of the membranes, and the remainder included two fetuses with pleural effusions and six with renal disease.

Table I indicates that, on the basis of the ultrasound criteria, there were I6 type I patients, six type 2 pa­tients, and 23 type 3 patients. The mean birth weights and gestational ages ar~ also included.

The frequency of oiigohydramnios in the patient population under study is also shown in Table I. The

presence of oligohydramnios was not restricted to fe­tuses thought to have pulmonary hypoplasia, but this condition was, however, seen more commonly in this type.

Fifteen of I6 type I patients (94%) predicted to de­velop pulmonary hypoplasia by our technique were confirmed as having the disease, and all except one had a lethal form of the disease. The patient with nonlethal pulmonary hypoplasia was delivered at 32 weeks' ges­tation and was discharged from the hospital after 62 days on a regimen of oxygen because of broncho­pulmonary dysplasia. The borderline measurements (type 2) provided a range of respiratory morbidities. Table II summarizes the findings in this group of pa­tients. The patients were delivered at different gesta­tional ages. However, this group comprised one case of lethal pulmonary hypoplasia, two cases of pneumo­thorax, and one case of bronchopulmonary dysplasia. The distribution of types I and 2 fetuses on the chest circumference normogram is shown in Fig. I.

Six of 23 infants with normal chest measurements had significant pulmonary complications. Three infants with birth weights of 550, 950 and I740 gm, respec­tively, had bronchopulmonary dysplasia. The smallest infant, clinically the most ill, was dischargeq from the hospital after II9 days on a home oxygen administra­tion program. The remaining three infants all had le­thal pulmonary hypoplasia. One fetus had autopsy findings of fetal hydantoin syndrome and the two others showed massive bilateral pleural effusions rec­ognized antenatally. The sensitivity, specificity, and pos­itive and negative predictive values of chest circumfer-

280 Nimrod et al.

ence measurements below the fifth percentile were 88%, 96%, 94%, and 93%, respectively. Cases in which pleural effusions were diagnosed antenatally were ex­cluded from these calculations.

In addition, the cephalic index was obtained in 10 of 16 infants below the fifth percentile. In only two of these infants was the measurement below I SD. This finding suggests that pulmonary hypoplasia secondary to decreases in amniotic fluid has a poor correlation with dolichocephaly.

Comment The antenatal prediction of pulmonary hypoplasia

has long eluded practicing obstetricians. The focus of many investigators has been on the development Qf animal models for research into the etiologic factors involved.6"8 In recent years, as ultrasound application has become widespread in clinical obstetrics, conscious comparison of the chest size of a fetus with that of the overllll fetal size has led us to establish initially a normo­gram for chest dimensions. • The normogram was used in this study to test the predictive value of" such a test on fetuses· at risk for developing pulmonary hy­poplasia. Th~ results of this prospective study demonstrate

that pulmonary hypoplasia can be predicted antenatally with confidence by fetal chest circumference measure­ments. In a~dition, we found that oligohydramnios and dolichocephaly are not useful antenatal markers of the development of pulmonary hypoplasia.

Our neonatal approach to clinical assessment was similar to that of Bhutani et aJ.9 We used criteria that were clinically based and correlated with significant re­spiratory morbidity. Fortunately, a large proportion of the surviving fetuses with significant respiratory mor­bidity was part of our neonatal follow-up program, and comprehensive information regarding their outcome could be obtained. It would seem from our data that fetuses whose measurements were around the fifth per­centile were truly in an intermediate position in ttteir outc~mes in terms of developing pneumothorax, pul­monary hypoplasia, and bronchopulmonary dysplasia requiring the ad~inistration of oxygen at home.

In this clinical study we did not use deoxyribonucleic acid studies10 to confirm the existence of pulmonary hypoplasia. However, we feel that the diagnosis was adequately established by the autopsy findings of lung

February 1988 Am J Obstet Gynecol

weight and lung weight/body weight ratios and by the histologic findings. VV,e recognize that pneumonia and pulmonary edema can interfere with this diagnosis by increasing the lung weight. Howev~r, additional water retention would not create false-positive find­ings, but rather false-negative findings, and therefore strengthen the credibility of our results.

In our previous report,' we highlighted the inability of our technique to assess pulmonary hypoplasia in association with bilateral pleural effusion. Therefore we felt that the cases of pleural effusion should be excluded from the calculation of sensitivity and speci­ficity in this study. In addition, if the fetal thorax was normal and the chest circumference was in the normal range, only one of 21 fetuses at risk died of pulmonary hypoplasia.

In summary, we have been able to demonstrate the clinical usefulness of chest circumference measure­ments determined by ultrasound to predict the exis­tence of pulmonary hypoplasia prospectively in patients with prolonged amniotic fluid leakage under 34 weeks' gestation.

REFERENCES l. Perlman M, Williams j, Hirsch M. Neonatal pulmonary

hypoplasia after prolonged leakage of amniotic fluid. Arch Dis Child 1976;51 :349.

2. Hislop A, Hey E, Reid L. The lung in congenital bilateral renal agenesis and dysplasia. Arch Dis Child 1979;54:32.

3. Nimrod C, Valena-Gittings F, Machin G, et al. The effect of very prolonged membrane rupture on fetal develop­ment. AM j 0BSTET GYNECOL 1984; 148:540.

4. Nimrod C, Davies D, Iwanicki S, et al. Ultrasound pre­diction of pulmonary hypoplasia. Obstet Gynecol 1986; 68:495.

5. Hadlock FP, Deter RL, Carpenter RJ, et al. Estimating fetal age: effect of head shape on BPD. AJR 1981;137:83.

6. Moessinger AC, FewellJE, Stark Rl, eta!. Lung hypoplasia and breathing movements following oligohydramnios in fetal lambs. In: Jones C, Nathanielsz P, eds. The physio­logical development of the fetus and newborn. London: Academic Press, 1985:293.

7. Wigglesworth J, Desai R. Effects on lung growth of cer­vical cord section in rabbit fetus. Early Hum Dev 1979; 3:51.

8. Moessinger AC. Fetal lung growth in experimental utero­abdominal pregnancy. Obstet Gynecol 1986;68:675.

9. Bhutani VR, Abbasi S, Weiner S. Neonatal pulmonary manifestations due to prolonged amniotic leak. Am J Per­inatal 1986;3:225.

10. Wiggleswonh J, Desai R. Use of DNA estimation for growth assessment in normal and hypoplastic fetal lungs. Arch Dis Child 1981;56:601. ·