Validity of transabdominal sonography in the detection of a two-vessel umbilical cord.

OBJECTIVE: To determine the validity of transabdominal ultrasound in the detection of a two-vessel and a three-vessel umbilical cord. METHODS: The ultrasound and pathology databases were collated between January 1, 1999, and December 31, 2000. Only those cases with ultrasound and pathology information concerning the number of vessels in the umbilical cord were included for analysis (group 1). In addition, 27 cases with a two-vessel umbilical cord were included from the ultrasound database before January 1, 1999, for which pathologic information was also obtained (group 2). RESULTS: A total of 1295 ultrasound/pathology reports were entered from January 1, 1999, through December 31, 2000; 268 cases did not have complete information, leaving 1027 for analysis (group 1). The visualization rate of the number of vessels in the umbilical cord increased from 15 to 17 weeks' gestation (74.1-97.6%; P <.001). The visualization rate remained stable from 17.0 to 35.9 weeks' gestation, and then declined to 83.3% (P <.01). The sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of a two-vessel umbilical cord were 85%, 99.7%, 85%, and 99.7%, respectively. CONCLUSION: The detection rate of either a two-vessel or three-vessel umbilical cord is best achieved between 17 and 36 weeks' gestation. In the majority of two-vessel umbilical cords that were called three-vessel, an appropriate transverse image of the umbilical cord was not obtained.

Sonographic determination of first trimester twin chorionicity and amnionicity.

OBJECTIVE: To determine the reliability of first trimester sonography in the detection of twin chorionicity and amnionicity. MATERIALS AND METHODS: Sets of twins (179) were evaluated sonographically in the first trimester. Chorionicity was determined by identifying the number of gestational sacs. The presence or absence of an amnion about each embryo/fetus was also recorded. The placentas for each case were evaluated to determine chorionicity and amnionicity. RESULTS: Of the 179 twin pairs, 158 were dichorionic/diamniotic; 19 were monochorionic/diamniotic, and two pairs were monochorionic/monoamniotic. Chorionicity and amnionicity were correctly determined in each case. CONCLUSION: The chorionicity of twin pregnancies can be determined from the time that the gestational sacs are visualized within the uterus. Transvaginal sonography can reliably determine the amnionicity of monochorionic twin pregnancies after 7 weeks, menstrual age.

Transvaginal sonographic evaluation of first-trimester placenta previa.

Our objective was to determine the relationship between the placenta and the internal cervical os in the first trimester. This study included ultrasound examinations performed between 9 and 13 weeks' gestation over a 28-month period. The position of the lower edge of the placenta with respect to the internal cervical os was recorded for each transvaginal ultrasound examination. A total of 77 out of 1252 (6.2%) patients had a first-trimester placenta previa; four cases persisted until term. There were no false-negative diagnoses. Our conclusion is that approximately 6.2% of patients will have a placenta previa in the first trimester. Transvaginal sonography can exclude a diagnosis of placenta previa after 9 weeks' gestation. The likelihood that a placenta previa will persist until term increases if the placenta covers the internal cervical os by > or = 1.6 cm.

The sonographic assessment of twin growth discordancy.

OBJECTIVE: To determine: 1) the frequency with which standard fetal biometry (head circumference [HC], abdominal circumference [AC], and femur length [FL]) and the transverse cerebellar diameter can be measured in twin pregnancies; and 2) the efficacy of fetal biometry using these measures in the detection of twin growth discordancy. METHODS: The study population consisted of 203 twin pregnancies reviewed retrospectively. The frequency with which standard biometry and the transverse cerebellar diameter could be obtained was recorded. Forty-nine twin pairs who were delivered within 3 weeks of their last ultrasound examination were divided into three groups based on birth weight differences: 20% or more, 10-19%, and less than 10%. The sensitivity, specificity, and predictive values of the specific fetal biometric measurements and of the sonographic estimation of fetal weight were assessed for this subgroup for the prediction of twin discordancy. RESULTS: The FL could be measured consistently throughout gestation, but the ability to measure the AC decreased after 35 weeks' gestation. The frequency with which HC and transverse cerebellar diameter could be measured decreased with advancing gestation. The transverse cerebellar diameter could be measured only in 91 of 151 and 14 of 49 pregnancies at 31-35 and 36-40 weeks' gestation, respectively. An intra-pair AC difference of 20 mm or more had a sensitivity and a positive predictive value of 83% for the detection of twin discordancy, defined as at least a 20% difference in birth weight. Estimated fetal weight had a sensitivity and positive predictive value of 92.9 and 72%, respectively. In contrast, a difference of 4 mm or more in the intra-pair transverse cerebellar diameter had a sensitivity of 28% and a positive predictive value of 50% in detecting twin weight discordancy. CONCLUSIONS: Appropriate twin fetal biometry can be measured throughout gestation. Estimated fetal weight has a higher sensitivity but a lower positive predictive value than AC for predicting twin growth discordancy.

Antenatal diagnosis of a congenital nasolacrimal duct cyst by ultrasonography: a case report.

With proximal and distal obstruction to the lacrimal drainage system, mucus accumulates forming a cyst. In order to diagnose a nasolacrimal duct cyst antenatally, the sonographer must image the region adjacent to the orbits.

Sonographic documentation of uterine retroversion mimicking uterine sacculation.

Uterine retroversion during the first trimester is quite common. However, as the uterus increases in size, self-correction usually occurs and the second trimester pregnant uterus becomes an abdominal organ. If anteversion does not occur, pelvic impaction will result. The prevalence of late first and early second trimester uterine impaction is approximately 1 in 3000 pregnancies. Our case documents sonographically the spontaneous resolution of a markedly retroverted uterus at 26 weeks' gestation.