Other than polyhydramnios and multiple fetuses, large masses in the uterus can lead the clinician to detect a uterus that is larger than anticipated by gestational age.
These masses include tumors such as molar pregnancies or partial moles with markedly enlarged and hydropic placentas or large chorioangiomas (Fig. 13–24). Tumors, such as large sacrococcygeal teratomas, will cause the uterus to enlarge because of both the tumor’s size and the associated polyhydramnios (Fig. 13–23). Fetuses with nonimmune hydrops are also subject to having enlarged Fetal tumors are rare, but can be a cause for an enlarged
uterus and excess amniotic fluid volume (Fig. 13–22, Fig.
13–23). These tumors include sacrococcygeal teratomas, intracranial teratomas, large fetal liver hemangiomas, re-nal hamartomas, and even placental tumors such as chorioangiomas.21–33 These can, in turn, lead to severe polyhydramnios associated with fetal hydrops and fetal
Figure 13–24 View of the uterus early in the second trimester show-ing no visible fetus. The uterus is filled with a solid mass with many small cystic spaces, typical of a complete mole.
Figure 13–25 The uterus is larger than dates because of a cystic mass (arrows) in the wall of the uterus, typical of a degenerating fibroid.
Figure 13–22 (A) Transverse view through the fetal head, showing large septated cystic hygromas of the nuchal region in a fetus with Turner’s syndrome. (B) Longitudinal view of the same fetus showing
the cystic hygromas as well as ascites and skin thickening consistent with lymphangiectasia.
A B
Figure 13–23 (A) Longitudinal view of the fetal body in the second trimester showing a large sacrococcygeal teratoma. The fetus is at risk for hydrops and polyhydramnios. (B) Same fetus seen using
three-dimensional surface reconstruction showing the fetus sitting on the large sacral tumor.
A B
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10. Benson CB, Coughlin BF, Doubilet PM. Amniotic fluid volume in large-for-gestational-age fetuses of nondiabetic mothers. J Ultra-sound Med 1991;10:149–151
11. Sohaey R, Nyberg DA, Sickler GK, Williams MA. Idiopathic polyhy-dramnios: association with fetal macrosomia. Radiology 1994;
190:393–396
12. Smith CV, Plambeck RD, Rayburn WF, Albaugh KJ. Relation of mild idiopathic polyhydramnios to perinatal outcome. Obstet Gynecol 1992;79:387–389
13. Pretorius DH, Drose JA, Dennis MA, Manchester DK, Manco-John-son ML. Tracheoesophageal fistula in utero: 22 cases. J Ultrasound Med 1987;6:509–513
14. Heydanus R, Spaargaren MC, Wladimiroff JW. Prenatal ultrasonic diagnosis of obstructive bowel disease: a retrospective analysis.
Prenat Diagn 1994;14:1035–1041
15. Hutchison AA, Drew JH, Yu VYH, et al. Nonimmunologic hydrops fetalis: a review of 61 cases. Obstet Gynecol 1982;
59:347–352
16. Chitkara U, Wilkins, Lynch L, Mehalek K, Berkowitz RL. The role of sonography in assessing severity of fetal anemia in Rh and Kell isoimmunized pregnancies. J Obstet Gynecol 1988;71:393–397 17. Mari G, Deter RL, Carpenter RL, et al. Noninvasive diagnosis by
Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. Collaborative Group for Doppler Assessment of the Blood Velocity in Anemic Fetuses. N Engl J Med 2000;342:
9–14
18. Goldstein RB, Filly RA. Prenatal diagnosis of anencephaly: spectrum of sonographic appearances and distinction from the amniotic band syndrome. AJR Am J Roentgenol 1988;151:547–550 19. Pretorius DH, Rumack CM, Manco-Johnson ML, et al. Specific
skele-tal dysplasias in utero: sonographic diagnosis. Radiology 1986;
195:237–242
20. Wong WS, Filly RA. Polyhydramnios associated with fetal limb ab-normalities. AJR Am J Roentgenol 1983;140:1001–1003
21. Brady K, Polzin WJ, Kopelman JN, Read JA. Risk of chromosomal abnormalities in patients with idiopathic polyhydramnios. Obstet Gynecol 1992;79:234–238
22. Jouppila P, Makarainen L, Rasanen J, Valkama M, Paavilainen T.
Aggressive direct treatment of a fetus with supraventricular tachy-cardia and hydrops fetalis. Ultrasound Obstet Gynecol 1993;3:
279–283
23. Hubinont C, Bernard P, Khalil N, et al. Fetal liver hemangioma and chorioangioma: two unusual cases of severe fetal anemia detected by ultrasonography and its perinatal management. Ultrasound Obstet Gynecol 1994;4:330–331
24. Williams FL, Williams RA. Placental teratoma: prenatal ultrasono-graphic diagnosis. J Ultrasound Med 1994;13:587–589
25. Sivit CJ, Hill MC, Larsen JW, Lande IM. Second-trimester polyhydramnios: evaluation with US. Radiology 1987;165:
467–469
26. Tonkin IL, Setzer ES, Ermocilla R. Placental chorioangioma: a rare cause of congestive heart failure and hydrops fetalis in the new-born. AJR Am J Roentgenol 1980;134:181–183
27. Treadwell MC, Sepulveda W, LeBlanc LL, Romero R. Prenatal diag-nosis of fetal cutaneous hemangioma: case report and review of the literature. J Ultrasound Med 1993;12:683–687
28. Kangarloo H, Diament MJ. Diagnostic oncology case study: cervical mass in a fetus associated with maternal hydramnios. AJR Am J Roentgenol 1983;140:507–509
29. Chervanak FA, Isaacson G, Blakemore KJ, et al. Fetal cystic hygroma: cause and natural history. N Engl J Med 1983;309:
822–825 placentas, which can contribute to the enlargement of the
uterus. Pelvic masses not associated with the pregnancy may also lead to the clinical finding of an enlarged uterus.
These include fibroid tumors, which can enlarge dramati-cally in the first part of pregnancy (Fig. 13–25). Also, ad-nexal masses such as ovarian cysts, dermoids, and other adnexal enlargements can result in the perception of an enlarged uterus by the clinician. Part of the evaluation of the pregnant uterus includes the assessment of the adnexa as well as the surrounding myometrium and cervix.
Summary
In conclusion, ultrasound is very successful at evaluating the pregnancy that is thought to be large for dates. In many cases, an explanation can be found (incorrect dates, multiple pregnancies, or a uterine fibroid). When polyhy-dramnios is detected, fetal biometry can be helpful to de-tect any growth acceleration leading to macrosomia, per-haps in a diabetic mother. A careful structural survey is necessary, however, when evaluating a fetus associated with polyhydramnios. When abnormalities are detected, it may be necessary to proceed with an amniocentesis or a percutaneous blood sampling for evaluation or treatment.
In most cases, a normal structural survey, even in associa-tion with significant polyhydramnios, results in a good outcome.
References
1. Benirschke K, Kim CK. Multiple pregnancy part one. N Engl J Med 1973;288:1276–1284
2. Blickstein I. Review: the twin–twin transfusion syndrome. Obstet Gynecol 1990;76:714–722
3. Bromley B, Frigoletto FD, Estroff JA, Benacerraf BR. The natural his-tory of oligohydramnios/polyhydramnios sequence in monochori-onic diamniotic twins. Ultrasound Obstet Gynecol 1992;2:317–
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4. Hecher K, Plath H, Bregenzer T, Hansmann M, Hackeloer BJ. Endo-scopic laser surgery versus serial amniocenteses in the treatment of severe twin–twin transfusion syndrome. Am J Obstet Gynecol 1999;180:717–724
5. Goldstein RB, Frilly RA. Sonographic estimation of amniotic fluid volume: subjective assessment versus pocket measurements. J Ul-trasound Med 1988;7:363–367
6. Phelan JP, Ahn MO, Smith CV, Rutherford SE, Anderson E. Amniotic fluid index measurements during pregnancy. J Repro Med 1987;
32:601–604
7. Barkin SZ, Pretorius DH, Beckett MK, et al. Severe polyhydram-nios: incidence of anomalies. AJR Am J Roentgenol 1987;
148:155–159
8. Damato N, Filly RA, Goldstein RB, et al. Frequency of fetal anom-alies in sonographically detected polyhydramnios. J Ultrasound Med 1993;12:11–15
9. Stoll CG, Alembik Y, Dott B. Study of 156 cases of polyhydramnios and congenital malformations in a series of 118,265 consecutive births. Am J Obstet Gynecol 1991;165:586–590
30. Perez-Aytes A, Sanchis N, Barbal A, et al. Short communication:
non-immunological hydrops fetalis and intrapericardial teratoma:
case report and review. Prenat Diagn 1995;15:859–863
31. Chervenak FA, Tortora M, Moya FR, Hobbins JC. Antenatal sono-graphic diagnosis of epignathus. J Ultrasound Med 1984;3:235–
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32. Benacerraf BR, Frigoletto FD. Prenatal sonographic diagnosis of iso-lated congenital cystic hygroma, unassociated with lymphedema or other morphologic abnormality. J Ultrasound Med 1987;6:63–66 33. Gross SJ, Benzi RJ, Sermer M, Skidmore MB, Wilson SR. Sacrococ-cygeal teratoma: prenatal diagnosis and management. Am J Obstet Gynecol 1987;156:393–396
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Accurate pregnancy dating is the most important step in prenatal management. Precise knowledge of gestational age is essential for the management of high-risk pregnan-cies and, in particular, fetal growth restriction. Although uterine size, as measured by the fundal height, provides a subjective assessment of the fetal size, ultrasound plays an integral and more precise role in confirming gestational age and has been shown to have an accuracy of 3 to 4 days when performed between 14 and 22 weeks of gestation.1 Several definitions exist in the literature for the diagno-sis of intrauterine growth restriction (IUGR). The definition that is most commonly used in clinical practice is an esti-mated fetal weight at less than the 10th percentile for ges-tational age. At this diagnostic threshold, ∼70% of fetuses will be small for gestational age (constitutionally small) and have no increase in perinatal morbidity or mortality.2 Using the fifth percentile as a cutoff for the diagnosis of IUGR may be more clinically applicable, given that perina-tal morbidity and morperina-tality have been shown to increase beyond this threshold.3Of all the ultrasound-derived bio-metric parameters, the abdominal circumference is the most sensitive indicator for growth restriction in the fetus.
An abdominal circumference of less than the 2.5th per-centile for gestational age carries a sensitivity of greater than 95% for the diagnosis of IUGR.4,5The growth profile of the abdominal circumference should therefore be moni-tored closely in fetuses at risk for growth abnormalities.
Furthermore, when estimating fetal weights by ultra-sound, the appropriate growth curves should be used.
Curves generated at high altitudes will underestimate IUGR by ∼50% for sea-level populations.6
When compared with appropriately grown fetuses matched for gestational age, IUGR fetuses have an in-creased risk of perinatal morbidity and mortality.7 Long-term follow-up studies have shown an increased incidence of physical handicap and neurodevelopmental delay in growth-restricted fetuses.8,9The presence of chronic meta-bolic acidemia in utero, rather than actual birth weight, appears to be the best predictor of long-term neurodevel-opmental delay.10 In pregnancies with growth-restricted fetuses, timing of the delivery is the most critical step in clinical management. Balancing the risk of prematurity with the risk of long-term neurodevelopmental delay is a serious challenge facing physicians involved in the care of these pregnancies.
Traditionally, the management of pregnancies with fe-tal growth restriction relied on cardiotocography for fefe-tal surveillance. During cardiotocography, the physician looks for heart rate variability as a sign of fetal well-being. Heart rate variability is the final result of the rhythmic, in-tegrated activity of autonomic neurons generated by or-ganized cardiorespiratory reflexes.11In growth-restricted fetuses, higher baseline rates, decreased long- and short-term variability, and delayed maturation of reactivity are seen in heart rate tracings.12,13These studies have relied on computer-generated analyses of fetal heart rate tracings in their evaluation. Unaided visual analyses of fetal heart rate records show limited reliability and reproducibility.14,15 Fur-thermore, the presence of overtly abnormal patterns of fetal heart rate tracings represents late signs of fetal dete-rioration.16,17 Relying on unaided visual analysis of car-diotocography as the only test of fetal surveillance in growth-restricted fetuses has come under criticism re-cently because it represents late signs of fetal deterioration and thus its sole use may not optimize long-term outcome of these pregnancies.
Doppler ultrasound has been shown to improve out-come in high-risk pregnancies.18The use of Doppler ultra-sound in the management of pregnancies with fetal growth restriction has received significant attention in the recent literature. Several cross-sectional and longitu-dinal studies have highlighted the fetal cardiovascular adaptation to hypoxemia and the progressive stages of such adaptation.19–24Findings from these studies and the use of Doppler ultrasound in the management of the growth-restricted fetus are discussed in the following section.