HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by JAZAYERI, A. Articles by SPELLACY, W. N. Search for Related Content PubMed PubMed Citation Articles by JAZAYERI, A. Articles by SPELLACY, W. N.

Macrosomia Prediction Using Ultrasound Fetal Abdominal Circumference of 35 Centimeters or More

From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Louisiana State University Medical Center, Shreveport, Louisiana, and Department of Obstetrics and Gynecology, College of Medicine, University of South Florida, Tampa, Florida.

Address reprint requests to: William N. Spellacy, MD, Suite 514, 4 Columbia Drive, Tampa, FL 33606

	Abstract

Top Abstract Methods Results Discussion References

 
Objective: To determine if birth weights greater than 4000 g can be predicted by ultrasound measurements of abdominal circumferences.

Methods: In 1996, 254 newborns delivered at Tampa General Hospital weighed at least 4000 g, 84 of whom had ultrasound examinations within 2 weeks of delivery. Those were compared with 84 neonates with recent ultrasounds who weighed less than 4000 g. Data were abstracted retrospectively from maternal medical records.

Results: The best linear predictor of birth weight was ultrasound measurement of abdominal circumference (AC), which had a correlation coefficient of 0.95. An AC measurement of 35 cm or more predicted 93% of macrosomic infants. Among 177 macrosomic infants born vaginally, 23 (13%) had shoulder dystocia. In that group, induction of labor was associated with a greater than three-fold increase in risk of shoulder dystocia (odds ratio [OR] 3.4, 95% confidence interval [CI] 1.4, 8.2; P < .01). Labor augmentation was not associated with increased risk of shoulder dystocia.

Conclusion: Abdominal circumference measurements were useful in screening for suspected macrosomia. An AC measurement of 35 cm or more identified more than 90% of macrosomic infants who were at risk for shoulder dystocia. Induction of labor in macrosomic patients increased the risk of shoulder dystocia.

Shoulder dystocia, one of the worst obstetric emergencies, occurs in 0.15–1.7% of vaginal deliveries. About half of shoulder dystocias happen to macrosomic infants (birth weights of 4000 g or more), yet frequency of macrosomia is less than 10%.¹ Thus, macrosomia is a very significant risk factor for shoulder dystocia. Studies showed that postdate pregnancies² and pregnancies in obese³ or diabetic women⁴ more commonly produce macrosomic infants, but few focused on single measurements that might alert obstetricians of macrosomia in individual patients.^5–7 Shoulder dystocia cannot always be predicted accurately, but predicting macrosomia identifies the population at the highest risk for shoulder dystocia, which enables obstetric care providers to evaluate pelvic bone size, especially pubic arch and outlet, to review procedures needed to manage shoulder dystocia, and to be certain that trained assistants will be available during delivery, if needed.

Those observations led investigators to search for antenatal predictors of shoulder dystocia. Cohen and associates⁸ reported recently that in diabetic pregnancies, ultrasound measurements of biparietal diameters subtracted from abdominal diameters of 2.5 cm or more predicted all cases of shoulder dystocia. The current study was designed to evaluate ultrasound measurements made close to delivery of infants weighing 4000 g or more to find an accurate and simple predictor of macrosomia.

	Methods

Top Abstract Methods Results Discussion References

 
The delivery log at Tampa General Hospital for 1996 was searched for women who delivered macrosomic infants, whose medical records were reviewed to abstract clinical and laboratory data. There were 3245 deliveries during the year, and 254 (7.8%) infants were macrosomic. Among those, 177 women delivered vaginally, 23 (13%) of whom had deliveries complicated by shoulder dystocia. Eighty-four women had ultrasound measurements within 2 weeks of delivery. Those were compared with 84 women who delivered infants less than 4000 g who had ultrasound measurements within 2 weeks of delivery. Diagnoses of diabetes were on the basis of ACOG criteria.⁹

Regression analysis was used to examine linear relationships between neonatal weight and ultrasound-estimated fetal weight, abdominal circumference (AC), biparietal diameter (BPD), and femur length (FL). Odds ratios (ORs) were calculated, and significance was tested using ² analysis. Logistic regression analysis was used to determine significant predictors of shoulder dystocia. Stepwise multiple regression was used to determine the best independent predictor of birth weight. Ordinal data were compared using ² and median tests. Continuous variables were compared using independent t test. Data were stored in the SPSS (Statistical Package for Social Sciences; SPSS, Inc., Chicago, IL), and all analyses were done with that system. P < .05 was significant.

	Results

Top Abstract Methods Results Discussion References

 
Population characteristics are listed in Table 1. Maternal weight and neonatal gestational age were significantly higher in the macrosomic group. Stepwise multiple regression analysis using birth weight as the dependent variable, and AC, BPD, and FL as independent variables, showed AC alone to be the best predictor of birth weight in macrosomic infants (r = 0.95, P < .001, Figure 1). An AC of at least 35 cm identified about 18% of infants born and 93% with birth weights of at least 4000 g. There were 23 shoulder dystocias among macrosomic infants. Abdominal diameters minus BPD measurements greater than 2.5 were not predictive of shoulder dystocia in diabetic or nondiabetic women. Table 2 shows predictability and reliability of a 35-cm AC for detecting macrosomia.

View larger version (15K): [in this window] [in a new window]   Figure 1. Linear relationship between ultrasound abdominal circumference and birth weight. An abdominal circumference of 35 cm or more identified more than 90% of macrosomic fetuses.

	Discussion

Top Abstract Methods Results Discussion References

 
Shoulder dystocia remains a serious obstetric emergency, and although not always predictable, it is clear that large fetuses are at greatest risk for it and more severe damage. Although macrosomia occurs in less than 10% of all pregnancies, half of shoulder dystocias occur in that group; therefore, detecting macrosomia before birth is important. Many studies examined antenatal prediction of birth weights using ultrasound measurements. Most of those studies agreed that neither birth weight nor shoulder dystocia can be predicted accurately, but infants with macrosomia, where the risk of shoulder dystocia is high, might be identifiable. Campbell and Wilkin¹⁰ emphasized the importance of ultrasound AC measurements in determining fetal size in 1975. A recent study by Smith et al¹¹ suggested that AC measurement is a better predictor of birth weight than fetal weight estimated by a combination of BPD, FL, and AC. We found similar results, except in this study, abdominal diameter minus BPD risk proposed by Cohen et al⁸ was not predictive of shoulder dystocia. That difference might be due to differences in the two populations and might indicate that the proposed measurements by Cohen are not always predictive of shoulder dystocia in different diabetic pregnancies.

One limitation of the present study is its retrospective design. Frequencies reported here are based on the assumption that the sample is representative of the entire population of live births. Our findings agree with those of Smith et al,¹¹ who found similar distributions of ultrasound measurements in more than 3500 live births. In that population, AC measurements of 35 cm occurred in 22%, identifying more than 90% of newborns with birth weights of at least 4000 g. In our study, all women with macrosomic neonates and shoulder dystocia had ultrasound measurements of AC greater than 35 cm.

Further analysis of macrosomic pregnancies and labor courses found an association between induction of labor and shoulder dystocia, independent of birth weight. McFarland et al¹² also reported a significantly higher rate of induction in women whose fetuses had shoulder dystocia. However, when they analyzed their data in the neonates with weights greater than 4000 g, that difference did not reach significance. Weeks et al,¹³ in pregnancies with suspected macrosomia, reported higher rates of induction and cesareans in the induction group. They did not test the influence of induction on frequency of shoulder dystocia. There are several possible explanations for the association between induction and shoulder dystocia compared with spontaneous labor, with or without augmentation, including differences in rates of labor progression, degrees of fetal and pelvic molding, and uterine power. Any of those factors alone or in combination could result in increased rates of shoulder dystocia, or it might be the result of bias. Obstetricians who induce labor in women with suspected macrosomic neonates might be more likely to initiate maneuvers, anticipating shoulder dystocia. Larger prospective studies are needed to better understand the association between induction and shoulder dystocia. Until then, on the basis of previous reports and present findings, labor induction in women with suspected macrosomia, for prevention of further growth and shoulder dystocia, should be questioned.

Identification of antenatal predictors of macrosomia and fetuses at high risk of shoulder dystocia will enable obstetricians to better prepare for it. The present results provided an AC measurement that can identify a relatively small portion of deliveries that are at high risk for macrosomia and shoulder dystocia. The accuracy of our retrospective study in this population of pregnant women needs to be tested in other populations to confirm its applicability. Because not all patients at risk for shoulder dystocia can be identified, all persons delivering infants must be trained in its appropriate management.

	Footnotes

 
PII S0029-7844(98)00520-1

Received May 27, 1998. Received in revised form September 21, 1998. Accepted October 8, 1998.

	References

Top Abstract Methods Results Discussion References

 
1. Cunningham FG, MacDonald PC, Gant NF, Leveno KL, Gilstrap LC III. Williams obstetrics. 19th ed. Norwalk, Connecticut: Appleton & Lange, 1993.

2. Arias F. Predictability of complications associated with prolongation of pregnancy. Obstet Gynecol 1987;70:101–6.[Abstract]

3. Di Cianni G, Benzi L, Bottone P, Volpe L, Orsini P, Murru S, et al. Neonatal outcome and obstetric complications in women with gestational diabetes: Effects of maternal body mass index. Int J Obes Relat Metab Disord 1996;20:445–9.[Medline]

4. Moore TR. Fetal growth in diabetic pregnancy. Clin Obstet Gynecol 1997;40:771–86.[Medline]

5. Spellacy WN, Miller S, Winegar A, Peterson PQ. Macrosomia—maternal characteristics and infant complications. Obstet Gynecol 1985;66:158–61.[Abstract]

6. Petrikovsky BM, Oleschuk C, Lesser M, Gelertner N, Gross B. Prediction of fetal macrosomia using sonographically measured abdominal subcutaneous tissue thickness. J Clin Ultrasound 1997; 25:378–82.[Medline]

7. Sood AK, Yancey M, Richards D. Prediction of fetal macrosomia using humeral soft tissue thickness. Obstet Gynecol 1995;85:937–40.[Abstract]

8. Cohen B, Penning S, Major C, Ansley D, Porto M, Garite T. Sonographic prediction of shoulder dystocia in infants of diabetic mothers. Obstet Gynecol 1996;88:10–3.[Abstract]

9. American College of Obstetricians and Gynecologists. Diabetes and pregnancy. ACOG technical bulletin no. 200. Washington DC: American College of Obstetricians and Gynecologists, 1994.

10. Campbell S, Wilkin D. Ultrasonic measurement of fetal abdomen circumference in the estimation of fetal weight. Br J Obstet Gynaecol 1975;82:689–97.[Medline]

11. Smith GCS, Smith MFS, McNay MB, Fleming JEE. The relation between fetal abdominal circumference and birthweight: Findings in 3512 pregnancies. Br J Obstet Gynaecol 1997;104:186–90.[Medline]

12. McFarland M, Hod M, Piper JM, Xenakis EMJ, Langer O. Are labor abnormalities more common in shoulder dystocia? Am J Obstet Gynecol 1995;173:1211–4.[Medline]

13. Weeks JW, Pitman T, Spinnato JA 2nd. Fetal macrosomia: Does antenatal prediction affect delivery route and birth outcome? Am J Obstet Gynecol 1995;173:1215–9.[Medline]

This article has been cited by other articles:

				D. L. Conway Obstetric Management in Gestational Diabetes Diabetes Care, July 1, 2007; 30(Supplement_2): S175 - S179. [Full Text] [PDF]

				T. L. Rasmussen The Use of Ultrasound to Identify Fetuses with Macrosoomia in Diabetic Pregnancies: A Review of Current Literature Journal of Diagnostic Medical Sonography, March 1, 2000; 16(2): 76 - 79. [Abstract] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by JAZAYERI, A. Articles by SPELLACY, W. N. Search for Related Content PubMed PubMed Citation Articles by JAZAYERI, A. Articles by SPELLACY, W. N.