Ultrasound of the cervix during pregnancy.

Translabial and transvaginal US are effective and accurate methods for imaging the uterine cervix. US accurately depicts the cervix, more accurately than digital examination, and helps to guide clinical management.

Stuck twin syndrome: outcome in thirty-seven consecutive cases.

OBJECTIVE: Our purpose was to further evaluate the role of serial amniocentesis in pregnancies complicated by the "stuck twin" syndrome. STUDY DESIGN: A cohort of 37 consecutive cases of stuck twin syndrome was followed up from 1986 through 1992. Evaluations included gestational age at diagnosis and at delivery, mean number of amniocenteses, volume of amniotic fluid withdrawn, placentation, perinatal complications, fetal survival, and neonatal follow-up. RESULTS: Five pregnancies were terminated, five had no intervention, and 27 underwent serial amniocenteses. The mean number of amniocenteses was 3.4 (range 1 to 6), and mean total amniotic fluid volume withdrawn was 5.8 L (range 0.75 to 4.0). In the serial amniocentesis group mean gestational age was 23.1 weeks (range 16 to 30) at diagnosis and 31.5 weeks (range 20 to 38) at delivery. Eighty-two percent had monochorionic placentas, and 36% had marginal or velamentous cord insertions. Infant survival was 39 of 54 (74%) in the serial amniocentesis group compared with four of 10 (40%) in the nonintervention group (relative risk 0.46, 95% confidence interval 0.24 to 0.90). CONCLUSION: Serial amniocentesis was associated with a 54% reduction in fetal and neonatal death in cases of stuck twin syndrome.

Fetal hyperechogenic bowel and Down's syndrome.

Hyperechogenic bowel was identified among 55 of 6781 (0.81%) fetuses prior to second-trimester genetic amniocentesis. Trisomy 21 was found in eight of the 55 (14.5%) fetuses identified with hyperechogenic bowel compared to 60 of 6726 (0.89%) fetuses with normal bowel echogenicity (p < 0.001). Hyperechogenic bowel carried a 16-fold greater risk for Down's syndrome than normal bowel echogenicity (relative risk 16.8, 95% confidence intervals 8.2-32.5). Chromosome abnormalities other than trisomy 21 were found in four additional fetuses with hyperechogenic bowel (two triploid and one each with 47,XXX; 45,X/47,XXX mosaicisim). Combining these four cases with the eight fetuses having trisomy 21, 21.8% (12 of 55) of fetuses with hyperechogenic bowel proved to have a chromosome abnormality. We conclude that hyperechogenic bowel is associated with chromosome abnormalities, particularly Down's syndrome, when detected during the second trimester.

Echogenic fetal bowel during the second trimester: clinical importance.

Clinical outcomes of 95 second-trimester fetuses prospectively considered to have echogenic bowel at ultrasound were compared with a control group of 110 consecutive second-trimester fetuses. Among the 95 fetuses in the study group, 64 (67%) had moderately echogenic (grade 2) or markedly echogenic (grade 3) bowel relative to the liver. Among the 110 fetuses in the control group, only two (1.8%) had moderately echogenic (grade 2) bowel; the rest (98.2%) had isoechoic (grade 0) or midly echogenic (grade 1) bowel relative to the liver. Adverse outcomes occurred in 45 of the 95 fetuses (47%) with echogenic bowel compared with eight of the 110 fetuses (7.27%) in the control group (P < .01; relative risk, 6.5; 95% confidence interval, 3.2, 13.1). Adverse outcomes included chromosomal abnormalities, intrauterine growth retardation, fetal demise, or other fetal anomalies. Within the study group, adverse outcomes occurred in 40 of the 64 fetuses (62%) with grade 2 or 3 bowel echogenicity, compared with five of the 31 fetuses (16%) with grade 1 echogenicity. Echogenic bowel is associated with an increased risk of adverse fetal outcome and this risk is confined primarily to grades 2 and 3 echogenicity.

Premaxillary protrusion: a sonographic clue to bilateral cleft lip and palate.

Sonograms from 49 fetuses with cleft lip, with or without cleft palate, were reviewed. Among 37 fetuses with adequate pathologic or clinical correlation, 10 (27%) demonstrated premaxillary protrusion, seen as a paranasal echogenic mass. Nine of ten fetuses with a paranasal echogenic mass proved to have bilateral cleft lip and cleft palate. Conversely, only two of 27 fetuses who did not show a paranasal echogenic mass proved to have bilateral cleft lip and cleft palate, and neither of these fetuses showed premaxillary protrusion at birth. Sonographic evaluation of the cleft alone erroneously misclassified eight fetuses with bilateral cleft lip and cleft palate as having unilateral clefts. Premaxillary protrusion is an important clue to the presence of cleft lip and cleft palate and may be more conspicuous than the cleft itself. Furthermore, the presence of a paranasal echogenic mass favors the presence of bilateral cleft lip and cleft palate, even when sonographic evaluation of the cleft itself suggests a unilateral cleft. This information should be useful in the detection and management of fetuses with suspected facial clefts.

Prenatal sonographic findings of trisomy 18: review of 47 cases.

Prenatal sonographic findings were reviewed in 47 consecutive fetuses with trisomy 18. One or more abnormalities, excluding choroid plexus cysts, were found in 39 fetuses (83%), including 21 of 29 (72%) fetuses examined between 14 and 24 weeks and all 18 (100%) fetuses examined after 24 weeks. Abnormalities most frequently detected before 24 weeks included cystic hygromas, nuchal thickening, and meningomyelocele. Intrauterine growth retardation, cardiac defects, and an enlarged cisterna magna were detected more frequently after 24 weeks than before 24 weeks (P < 0.05). Intrauterine growth retardation was the single most common abnormality, detected in 51% of all fetuses and 89% of fetuses examined after 24 weeks. Choroid plexus cysts were identified in 25% (12 of 47) of fetuses, including 11 of 29 (38%) fetuses seen before 24 weeks. Additional abnormalities were identified in 10 of 12 (83%) fetuses with choroid plexus cysts; one of the two remaining fetuses showed clenched hands and a cardiac anomaly at autopsy, and the other showed unusually large, multiple choroid plexus cysts. Awareness of the type of anomalies and the usual menstrual age of diagnosis in fetuses with trisomy 18 should improve patient counseling and prenatal detection of fetuses considered at risk for this disorder.

Low birth weight and preterm delivery in relation to early-gestation vaginal bleeding and elevated maternal serum alpha-fetoprotein.

OBJECTIVE: To determine whether early-gestation vaginal bleeding and elevated maternal serum alpha-fetoprotein (MSAFP) are independent risk factors for adverse infant outcomes. METHODS: We conducted a cohort study of 201 women with an elevated MSAFP (at least 2.0 multiples of the median [MOM]) and a second-trimester ultrasound evaluation at Swedish Hospital Medical Center between January 1989 and March 1991, and 211 women with MSAFP levels below 2.0 MOM who had also undergone ultrasound evaluations during the same period. RESULTS: Stratified analyses demonstrated that early-gestation bleeding and elevated MSAFP were independent risk factors for the delivery of both preterm and low birth weight infants. Compared with women with no history of early-gestation bleeding or elevated MSAFP, women with early-gestation bleeding alone had a relative risk (RR) of preterm delivery of 4.3 (95% confidence interval [CI] 1.5-12.1); non-bleeders with elevated MSAFP had an RR of 4.6 (95% CI 1.9-10.9). A combined history of early-gestation bleeding and elevated MSAFP was associated with an almost sixfold increased risk of preterm delivery (RR 5.8; 95% CI 2.2-15.6). Analyses restricted to women with normal-appearing appearing placentas by second-trimester ultrasound evaluations yielded similar results. CONCLUSIONS: These findings support an earlier report documenting the independence of early-gestation bleeding and elevated MSAFP as predictors of adverse infant outcomes.

Elevated maternal serum alpha-fetoprotein levels and midtrimester placental abnormalities in relation to subsequent adverse pregnancy outcomes.

OBJECTIVE: Unexplained elevations of maternal serum alpha-fetoprotein levels in the second trimester of pregnancy are associated with adverse pregnancy outcomes, including intrauterine growth retardation, preterm delivery, preeclampsia, and abruptio placentae. In addition, elevations of maternal serum alpha-fetoprotein have been associated with placental lesions detected during second-trimester ultrasonographic evaluations. We examined the relationship between adverse pregnancy outcomes and unexplained elevations of maternal serum alpha-fetoprotein and placental abnormalities in the second trimester of pregnancy. STUDY DESIGN: During the period from January 1989 to March 1991 we conducted a cohort study of 201 women with an elevated maternal serum alpha-fetoprotein (> or = 2.0 multiples of the median) and a second-trimester ultrasonographic evaluation at Swedish Hospital Medical Center and 211 women with normal maternal serum alpha-fetoprotein levels who had also undergone ultrasonographic evaluation at the same institution. All women in this investigation had singleton pregnancies without fetal anomalies. RESULTS: Elevated maternal serum alpha-fetoprotein was associated with the following adverse pregnancy outcomes: low birth weight (adjusted risk ratio 3.7), preterm delivery (adjusted risk ratio 3.6), intrauterine growth retardation (adjusted risk ratio 4.0), preeclampsia (adjusted risk ratio 3.8) and abruptio placentae (adjusted risk ratio 4.8). Placental abnormalities detected during second-trimester ultrasonographic evaluations were also associated with adverse pregnancy outcomes: low birth weight (adjusted risk ratio 2.0), preterm delivery (adjusted risk ratio 2.3), intrauterine growth retardation (adjusted risk ratio 1.4), and abruptio placentae (adjusted risk ratio 9.0). A joint positive history of second-trimester elevations of maternal serum alpha-fetoprotein and placental abnormalities was more strongly associated with the following adverse infant outcomes: low birth weight (adjusted risk ratio 6.9), preterm delivery (adjusted risk ratio 5.6), and intrauterine growth retardation (adjusted risk ratio 5.3). CONCLUSIONS: Unexplained elevated levels of maternal serum alpha-fetoprotein and placental abnormalities detected in the second trimester of pregnancy are associated with particularly poor pregnancy outcome. Careful examination for placental abnormalities should be part of the evaluation of elevated maternal serum alpha-fetoprotein.

Paranasal echogenic mass: sonographic sign of bilateral complete cleft lip and palate before 20 menstrual weeks.

A paranasal echogenic mass identified at ultrasound performed during the second trimester was the initial and primary clue to the presence of bilateral complete cleft lip and palate in four fetuses. Referral had been for dating purposes in three cases and because of high maternal serum alpha-fetoprotein level in one. Genetic amniocentesis revealed deletion of the 15th chromosome in one case. The clefts were small and difficult to visualize; the finding of the echogenic mass (representing a premaxillary protrusion) therefore added confidence to the diagnosis.

Varix of the fetal intra-abdominal umbilical vein: comparison with normal.

To compare the normal extrahepatic portion of the fetal intra-abdominal umbilical vein (FIUV) with varix of the FIUX, we prospectively measured the diameter of the FIUV in 150 uncomplicated second and third trimester pregnancies and compared these results with retrospective review of nine fetuses with varix of the FIUV as an isolated prenatal sonographic finding. The diameter of the normal FIUV increases linearly from approximately 3 mm at 15 menstrual weeks to approximately 8 mm at term (R = 0.92). The nine fetuses with FIUV varix had a FIUV diameter 6 to 12 standard deviations above the mean for age. Four (44%) of the nine fetuses with FIUV varix subsequently died, including one with trisomy 21. One of the remaining fetuses developed severe hydrops 2 weeks after the initial detection of the FIUV varix. FIUV varix appears to carry an increased risk of adverse fetal outcome, including fetal demise.

Transcervical chorionic villus sampling and midtrimester oligohydramnios.

To study the possible association between transcervical chorionic villus sampling and midtrimester oligohydramnios, we conducted a prospective cohort study of all women who were seen for genetic counseling in the first trimester during a 2-year period. Women who chose chorionic villus sampling were compared with women who chose traditional amniocentesis for incidence of midtrimester oligohydramnios. Of 442 women exposed to chorionic villus sampling with a normal fetal karyotype, severe oligohydramnios developed in 12 (2.7%) at 16 to 23 weeks' gestation. None of the 391 women with normal fetal karyotypes who were counseled at the same time in pregnancy but who chose amniocentesis had oligohydramnios at the time of amniocentesis (p = 0.01). A nested case-control analysis was performed within the chorionic villus sampling group to evaluate risk factors associated with midtrimester oligohydramnios. Midtrimester oligohydramnios occurring after chorionic villus sampling was associated with postprocedure bleeding and elevated maternal serum alpha-fetoprotein (p less than 0.01). There were no perinatal survivors with midtrimester oligohydramnios.

Single umbilical artery. Prenatal detection of concurrent anomalies.

Prenatal sonographic findings were reviewed in 30 fetuses with a single umbilical artery (SUA) to determine the reliability of ultrasound for detecting concurrent anomalies. Additional anomalies were identified in 15 fetuses, including 3 fetuses with minor anomalies and 12 fetuses with major or multiple concurrent anomalies. Minor anomalies observed in 3 fetuses included 1 case each of pelvic kidney, unilateral absent kidney, and mild cerebral ventricular dilatation. Major abnormalities detected in 12 fetuses involved a variety of organ systems and included cardiac defects, holoprosencephaly, skeletal dysplasia, hydrocephalus, omphalocele, hydrothorax, enlarged cisterna magna, and diaphragmatic hernia. Clinical and pathologic correlation showed that all fetuses were correctly categorized regarding the presence of other anomalies; none of the 15 fetuses in whom an SUA was considered an isolated finding had a significant anomaly at birth. Chromosome abnormalities were found in 6 of 12 fetuses with major abnormalities but in none of the 18 remaining fetuses. We conclude that prenatal ultrasound can reliably identify major concurrent anomalies in fetuses with SUA. In the absence of additional anomalies, prenatal detection of SUA should not alter obstetric management.

Enlarged cisterna magna and the Dandy-Walker malformation: factors associated with chromosome abnormalities.

Thirty-three fetuses with an enlarged cisterna magna (10 mm or more) were evaluated to determine factors that might be associated with an underlying chromosome abnormality. Eighteen fetuses (55%) proved to have a chromosome abnormality, including trisomy 18 or trisomy 18 variant (12), trisomy 13 (three), Turner syndrome (one), or other rearrangements (two). Among various risk factors analyzed, the absence of ventricular dilatation correlated most strongly with a chromosome abnormality. Chromosome abnormalities were found in 17 of 22 fetuses (77%) lacking ventricular dilatation, compared with only one of 11 fetuses (9%) with ventricular dilatation (P less than .001). Other factors statistically associated (P less than .01) with an underlying chromosome abnormality included mild enlargement of the cisterna magna (10-14 mm), concurrent anomalies detected sonographically, and fetal growth retardation. However, stepwise logistic regression showed that only the absence of ventricular dilatation and the presence of concurrent anomalies were significant when multiple factors were evaluated. These observations support the utility of evaluating the cisterna magna as part of a routine anatomical survey.

Sirenomelia associated with a "vanishing twin".

A case is presented of twin gestation in which one gestational sac was completely resorbed and the remaining twin was subsequently found to be sirenomelic. First-trimester prenatal ultrasound examination demonstrated a second gestational sac that disappeared 2 weeks later. The sonographic features that led to the diagnosis of sirenomelia in the remaining fetus included severe renal dysgenesis, persistently apposed lower extremities, and absence of fibulae. Postmortem examination, including angiographic studies of the fetus, revealed caudal dysgenesis and a single umbilical artery that arose from the abdominal aorta. Sirenomelia occurs more frequently in twin gestations than in singletons. This case suggests that the association between twinning and sirenomelia may be greater than is currently recognized. Two hypotheses are given to explain this association.

Meckel-Gruber syndrome. Importance of prenatal diagnosis.

Prenatal sonographic findings are reported in six fetuses with the Meckel-Gruber syndrome to illustrate the variety of sonographic findings associated with this disorder and to emphasize the importance of prenatal sonography in helping to establish the correct diagnosis. All six fetuses demonstrated evidence of renal cystic dysplasia. In five cases the kidneys were large and echogenic, demonstrating small discrete cysts in the range of 2 to 5 mm. The remaining fetus demonstrated unilateral renal cystic dysplasia and contralateral renal agenesis. Oligohydramnios was noted in all cases and was evident as early as 14 weeks. An occipital cephalocele was demonstrated on sonography in each case although the size and contents of the cephalocele varied significantly. Two fetuses, both in the same family, also demonstrated a cystic mass in the posterior fossa and partial absence of the cerebellum consistent with a Dandy-Walker variant or cerebellar hypoplasia. The concurrence of marked oligohydramnios and bilateral severe renal anomalies should initiate a search for anomalies of the central nervous system indicative of the Meckel-Gruber syndrome. Recurrence of Meckel-Gruber syndrome may be evaluated as soon as 14 weeks, but it may not be reliably excluded until 20 weeks.

Translabial ultrasound of the third-trimester uterine cervix. Correlation with digital examination.

This prospective blinded study compared translabial ultrasound (TLU) and digital palpation of the cervix among women whose cervix could not be visualized adequately or at all with transabdominal ultrasound during the third trimester of pregnancy. The cervical canal and internal cervical os were adequately visualized during 109 of 113 TLUs (96%). The TLU was well tolerated by the patients; only two patients refused the TLU pending discussion of the technique with their obstetrician. Among 43 examinations of patients without clinical cervical effacement, TLU showed a cervical length of 2.5 to 4.2 cm (mean, 2.9 cm). An excellent correlation (R = 0.90) was noted between cervical length on TLU and percentage of cervical effacement on digital examination. The correlation between amount of cervical dilatation on TLU and on digital examination was not high (R = 0.58). We conclude that the measurements of cervical length on TLU correlate well with the amount of cervical effacement on digital examination and that TLU provides a rapid and well-tolerated alternative technique to visualize the third-trimester uterine cervix.

The "stuck twin" phenomenon: ultrasonographic findings, pregnancy outcome, and management with serial amniocenteses.

Thirteen consecutive twin pregnancies affected by the "stuck twin" phenomenon were reviewed to determine the potential benefit of serial amniocenteses. The fetal survival rate for the eight pregnancies that underwent serial amniocenteses was 69% (11 of 16 fetuses). This is significantly improved compared with a fetal survival rate of 20% among the five preceding pregnancies managed without serial amniocenteses at the same institution (p = 0.01). It is also markedly improved compared with a combined fetal survival rate of 16% among 48 previously reported pregnancies with the stuck twin phenomenon managed without serial amniocenteses (p less than 0.0001). Survival correlated with the absence of concomitant pregnancy complications (i.e., maternal hypertension or intractable labor) and with the absence of severe fetal structural abnormalities. Procedural complications occurred in three of eight pregnancies (37.5%) managed with serial amniocenteses and was attributed as a cause of fetal death in one case. Two of 11 survivors (18%) had complications after serial amniocenteses including brain infarction and renal tubular necrosis. Serial amniocenteses may significantly improve the survival rate of twin gestations affected by the stuck twin phenomenon but may be associated with complications among survivors.

Prenatal sonographic findings of Down syndrome: review of 94 cases.

Prenatal ultrasound findings were reviewed in 94 consecutive fetuses with proved Down syndrome (trisomy 21) during a 6-year period at a single institution. One or more abnormalities were found in 31 fetuses (33%), including two of 11 fetuses seen before 14 weeks, 17 of 68 fetuses seen between 14-24 weeks, and 12 of 15 fetuses seen after 24 weeks. Major anomalies detected included cardiac defects (five), duodenal atresia (four), cystic hygromas (four), omphalocele (two), hydrops (two), and hydrothorax (one). Nuchal thickening was observed in five fetuses, including four of 25 second-trimester fetuses evaluated prospectively during the last 2 years of the study. Mild cerebral ventricular dilatation (three) and hyperechogenic bowel (five) are new findings that have not been generally associated with Down syndrome. A variety of prenatal sonographic abnormalities may be associated with Down syndrome, and the frequency of detecting most abnormalities increases with menstrual age. Anomalies more frequently detected before 20 weeks include cystic hygromas, nuchal thickening, and hyperechogenic bowel. Awareness of the sonographic findings associated with Down syndrome should result in improved detection of this disorder.

Femur length shortening in the detection of Down syndrome: is prenatal screening feasible?

The potential utility of screening for femur length shortening in prenatal detection of Down syndrome (trisomy 21) was evaluated by comparing 49 consecutive fetuses with Down syndrome with 572 chromosomally normal fetuses before genetic amniocentesis. Ratios of measured femur length/predicted femur length and biparietal diameter/femur length were calculated for each fetus. The predicted femur length was calculated from a regression equation relating the biparietal diameter and femur length derived from a sample control group. With this normal regression equation, 7 of 49 (14.3%) fetuses with Down syndrome had short femur lengths (measured femur length/predicted femur length ratio of less than or equal to 0.91) compared with 35 of 572 (6.1%) fetuses with a normal karyotype (p less than 0.05). However, the maximum positive predictive value for identification of Down syndrome based on short femur lengths was only 0.93% for a high-risk population (prevalence of Down syndrome, 1:250) and 0.33% for a low-risk population (prevalence of Down syndrome, 1:700). We conclude that ultrasonographic screening of short femur length is less effective for prenatal detection of Down syndrome than initially suggested.

The clinical significance of uterine leiomyomas in pregnancy.

In a retrospective review of 6706 pregnancies between 1981 and 1985, uterine leiomyomas were documented by antenatal sonography in 93 (1.4%) patients. The obstetric records and sonograms of patients with documented leiomyomas were reviewed and compared with data from matched control patients managed at our institution during the same time period. Among the 93 patients with leiomyomas, 14 (15.1%) had one or more leiomyomas subjacent to the maternal surface of the placenta. Significantly, eight of 14 (57%) of these patients with retroplacental leiomyomas subsequently developed abruptio placentae, which resulted in the deaths of four fetuses. Conversely, among the remaining 79 patients whose leiomyomas were not retroplacental, abruptio placentae occurred in only two patients (2.5%), neither of which resulted in fetal death. Clinically significant pain requiring narcotic analgesia developed in 14 of 93 (15.1%) patients and premature labor occurred in 20 of 93 (21.5%); pain and premature labor correlated positively with the size of the largest myoma. Delivery by cesarean section and vacuum assistance occurred significantly more frequently in patients with leiomyomas than in those without documented leiomyomas. In this population uterine myomas did not significantly alter the incidence of intrauterine growth retardation and low Apgar scores.