Cervical length at 23 weeks in triplets: prediction of spontaneous preterm delivery.

OBJECTIVES: To establish the distribution of cervical length at 23 weeks of gestation in triplet pregnancies and to examine the relation to preterm delivery before 33 weeks. METHODS: Cervical length was measured by transvaginal sonography at 23 (range 22-24) weeks of gestation in 43 triplet pregnancies. The distribution of cervical length was determined and the relationship between cervical length and the rate of spontaneous preterm delivery before 33 weeks was calculated. RESULTS: The cervical length distribution was skewed to the left with a median of 34 mm. The rate of spontaneous labor and delivery before 33 weeks increased exponentially with decreasing cervical length at 23 weeks from 8% at 36-48 mm, to 11% at 26-35 mm, 33% at 16-25 mm and 67% at 15 mm or less. Cervical length was < or = 30 mm, < or = 25 mm and < or = 15 mm in 37%, 16% and 8% of cases, respectively, and the corresponding sensitivities in the prediction of spontaneous delivery before 33 weeks were 67%, 50% and 33%. CONCLUSIONS: In triplet pregnancies, measurement of cervical length provides a useful prediction of risk for spontaneous early preterm delivery.     

Cervical length and funneling at 23 weeks of gestation in the prediction of spontaneous early preterm delivery.

OBJECTIVES: To establish the relationship of cervical length at 23 weeks of gestation to the risk of spontaneous delivery before 33 weeks and to determine the possible additional risk if funneling is present. METHODS: During a 36-month period, 6819 women with singleton pregnancies underwent transvaginal sonographic cervical assessment at 22-24 weeks as a screening test for preterm delivery. The distribution of cervical length and the prevalence of funneling, defined as dilatation of the internal os of > or = 5 mm in width, were established. Women who underwent cervical cerclage, iatrogenic preterm delivery or were lost to follow-up were excluded from further analysis. In the remaining 6334 pregnancies, logistic regression was used to examine the contribution of cervical length and funneling to the risk of spontaneous preterm delivery before 33 weeks. RESULTS: The median cervical length was 36 mm and in 1.6% of cases the length was < or = 15 mm. There was a significant inverse association between cervical length and percentage rate of spontaneous delivery before 33 weeks. Funneling of the internal os was present in about 4% of pregnancies and the prevalence decreased with increasing cervical length from 98% when the length was < or = 15 mm to about 25% for lengths of 16-30 mm and less than 1% at lengths of > 30 mm. The rate of preterm delivery was 6.9% in those with funneling compared to 0.7% in those without funneling (chi2 = 86.7; P < 0.0001). However, logistic regression analysis demonstrated that funneling did not provide a significant additional contribution to cervical length in the prediction of spontaneous delivery before 33 weeks (odds ratio for short cervix = 24.9, Z = 4.43, P < 0.0001; odds ratio for funneling = 1.8, Z = 0.84, P = 0.40). CONCLUSION: In the prediction of preterm delivery, funneling does not provide any significant contribution in addition to cervical length.     

How to identify twins at low risk of spontaneous preterm delivery.

OBJECTIVE: The aim of this study was to evaluate transvaginal sonographic assessment of cervical length at 23 weeks as a screening test for spontaneous preterm delivery in order to define a cut-off value that could be used to select twin pregnancies at low risk of spontaneous preterm delivery. METHODS: In a prospective multicenter study of 383 twin pregnancies included before 14 + 6 weeks a cervical scan with measurement of the cervical length was performed at 23 weeks' gestation. The results were blinded for the clinicians if the cervical length was > or = 15 mm. The rates of spontaneous delivery at different cut-off levels of cervical length were determined. RESULTS: Eighty-nine percent of the twins had dichorionic placentation and 58% were conceived after assisted reproduction. The rate of spontaneous preterm delivery was 2.3% (1.5% for dichorionic (DC) and 9.1% for (MC) monochorionic twins) before 28 weeks and 18.5% (17.1% for DC and 29.5% for MC twins) before 35 weeks. The screen-positive rate was 5% for a cervical length < or = 20, 7-8% at < or = 25, 16-17% at < or = 30 and 34-48% at < or = 35 mm depending on chorionicity. The false-negative rate (1 - negative predictive value) ranged from 1.2% at 28 weeks to 18.6% at 35 weeks for all twins. Receiver-operating characteristics curves showed that the sensitivity increased with declining gestational age with cut-off levels of highest accuracy at 21 mm for 28 weeks and 29 mm for 33 weeks. CONCLUSIONS: Cervical length measurement at 23 weeks of gestation is a good screening test for predicting twins at low risk of preterm and very preterm delivery, especially in DC twins. The present results suggest that a cut-off of 25 mm should be recommended.     

Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high-risk pregnancies?

OBJECTIVE: To determine whether high-risk patients manifest cervical length < 25 mm on transvaginal ultrasound before 14 weeks of gestation, and if this finding is predictive of preterm delivery. METHODS: Asymptomatic pregnancies at high risk for preterm birth were followed prospectively from 10 + 0 weeks to 13 + 6 weeks with transvaginal sonographic measurement of the cervix. A cervical length < 25 mm was considered a short cervix at this gestational age and at the follow-up ultrasound examinations, performed between 14 and 24 weeks. The primary outcome was preterm birth at < 35 weeks of gestation. RESULTS: One hundred and eighty-three pregnancies met the study criteria and were included in the analysis. Only 10 (5%) patients had a cervix < 25 mm before 14 weeks. The sensitivity, specificity and positive and negative predictive values of a short cervix were 14%, 97%, 50%, and 82%, respectively (relative risk, 2.8; 95% confidence interval, 1.4-5.6). The mean transvaginal sonographic cervical length before 14 weeks of gestation was 33.7 +/- 6.9 mm in pregnancies which delivered preterm (n = 36), and 35.0 +/- 6.8 mm in those delivering at term (n = 147) (P = 0.3). Follow-up transvaginal ultrasound examination of the cervix to 24 weeks revealed that the average gestational age at which a short cervix was detected was 18.7 +/- 2.9 weeks. CONCLUSION: A cervical length < 25 mm on transvaginal sonographic assessment rarely occurs before 14 weeks even in high-risk patients destined to deliver preterm; in these patients cervical changes predictive of preterm birth develop mostly after this gestational age.     

Prediction of preterm birth by second trimester cervical sonography in twin pregnancies.

OBJECTIVES: To determine the predictive value of sonographic cervical length and of funneling for spontaneous preterm delivery (PTD) in twin pregnancies under 26 weeks' gestation. METHODS: Women with twin pregnancies were studied prospectively with transvaginal or translabial ultrasound of the cervix from 18 to 26 weeks' gestation. Exclusion criteria were: signs of preterm labor, prophylactic cervical cerclage, placenta previa, or severe congenital fetal anomaly. The primary outcome was spontaneous preterm birth at < 35 weeks' gestation. RESULTS: Sixty-five twin pregnancies were analyzed, of which 23% (15/65) delivered preterm. Cervical ultrasound examination was performed by 22 weeks' gestation in 75% and by 24 weeks' gestation in 91% of women. Cervical length < or = 25 mm and < or = 30 mm was associated with sensitivities of 27% and 53%, respectively, and with 67% and 62% rates of PTD, respectively (R.R. 4.6, C.I. 2.0-10.3 and R.R. 3.6, C.I. 1.6-7.8, respectively). A cervical length > 35 mm was associated with only a 4% rate of PTD (R.R 0.13; C.I. 0.02-0.93). Of 10 women (15%) with any cervical funneling, 70% delivered preterm, all under 32 weeks' gestation. By logistic regression analysis, both short cervix < or = 30 mm and any funneling were strongly predictive of PTD. CONCLUSIONS: Both cervical length < or = 30 mm and cervical funneling in twin pregnancies under 26 weeks' gestation are independently and strongly associated with high risk for preterm birth. A long cervix, of length > 35 mm, is associated with very low risk (4%) for preterm birth.     

Ultrasound assessment of cervical length in threatened preterm labor.

OBJECTIVE: More than 70% of women presenting with threatened preterm labor do not progress to active labor and delivery. The aim of this study was to investigate the hypothesis that in women with threatened preterm labor, sonographic measurement of cervical length helps distinguish between true and false labor. METHODS: We examined 216 women with singleton pregnancies presenting with regular and painful uterine contractions at 24-36 (mean, 32) weeks of gestation. Women in active labor, defined by the presence of cervical dilatation > or = 3 cm, and those with ruptured membranes were excluded. On admission to the hospital a transvaginal scan was performed to measure the cervical length. The subsequent management was determined by the attending obstetrician. The primary outcome was delivery within 7 days of presentation. RESULTS: In 173 cases the cervical length was > or = 15 mm and only one of these women delivered within 7 days. In the 43 cases with cervical length < 15 mm delivery within 7 days of presentation occurred in 16 (37%) including 6/14 (42%) treated with tocolytics and 10/29 (35%) managed expectantly. Logistic regression analysis demonstrated that the only significant contributor in the prediction of delivery within 7 days was cervical length < 15 mm (odds ratio = 101, 95% CI 12-800, P < 0.0001) with no significant contribution from ethnic group, maternal age, gestational age, body mass index, parity, previous history of preterm delivery, cigarette smoking, contraction frequency or use of tocolytics. CONCLUSIONS: In women with threatened preterm labor, sonographic measurement of cervical length helps distinguish between true and false labor.     

Predicting preterm delivery in asymptomatic patients with prior preterm delivery by measurement of cervical length and phosphorylated insulin-like growth factor-binding protein-1.

OBJECTIVE: To evaluate the efficacy of cervical length measurement in combination with a bedside assessment of phosphorylated insulin-like growth factor-binding protein-1 (phIGFBP-1) as a predictor of preterm delivery in asymptomatic pregnant women with a history of preterm birth. METHODS: Cervical length was measured using transvaginal sonography at 22-24 weeks of gestation in 105 singleton pregnancies and a rapid strip test was performed to detect phIGFBP-1 in cervical secretions from 24 to 34 weeks. Receiver-operating characteristics (ROC) curves were constructed to compare the performance of phIGFBP-1 at different gestational ages, and cervical length at 22-24 weeks, in predicting preterm delivery. RESULTS: The rate of spontaneous delivery before 37 and 34 weeks was 23.8% and 11.4%, respectively. Women with cervical lengths less than 20 mm had a risk of spontaneous preterm delivery before 34 and 37 weeks of 43.5% and 69.6%, respectively. The performance of phIGFBP-1 levels as a predictor of preterm delivery was significantly higher when the test was carried out at 30 weeks' gestation. Cervical assessment in combination with phIGFBP-1 at 30 weeks had the steepest ROC curve (area under the curve=0.93; 95% CI, 0.88-0.98, P<0.001). CONCLUSION: Both cervical length and phIGFBP-1 measurement are useful in the prediction of preterm delivery in patients with a history of preterm birth and the combined method of measuring cervical length at 22-24 weeks and phIGFBP-1 at 30 weeks improves upon either method used alone.     

Cervical length at 18-22 weeks of gestation for prediction of spontaneous preterm delivery in Hong Kong Chinese women.

OBJECTIVE: To assess the value of a single cervical length measurement by transvaginal sonography (TVS) at the time of mid-trimester anomaly scan for predicting spontaneous preterm delivery (SPD) among Chinese women. METHODS: A prospective observational study was carried out involving 2880 subjects with singleton pregnancies and confirmed gestational age. Cervical length was measured at 18-22 weeks of gestation. RESULTS: The incidence of SPD < 34 weeks and < 37 weeks were 0.7% and 3.7%, respectively. Women with SPD < 34 weeks and SPD < 37 weeks had shorter median cervical lengths (32.6 mm and 36.2 mm, respectively) than those with term deliveries (37.6 mm) (P = 0.006 and 0.025, respectively). The predictive performance of cervical length was better for SPD < 34 weeks compared with < 37 weeks. A cervical length < or = 27 mm, which corresponded to the 4th centile, occurred in 36.8%, 62.5% and 100% of those with SPD < 34, < 30 and < 26 weeks, respectively. The positive likelihood ratio (LR) of a cervical length < or = 27 mm in predicting SPD < 34 weeks was 9.8. Using logistic regression, both short cervix and funneling were independent predictors for SPD < 34 weeks of gestation. The coexistence of funneling and a cervical length < or = 27 mm gave a positive predictive value (PPV) and LR of SPD < 34 weeks of 14.7% and 26.0, respectively. CONCLUSIONS: Mid-trimester cervical length is predictive of SPD in Chinese women. However, given the low PPV of a short cervical length, its clinical utility is still limited in low-risk populations.     

Thermocoagulation for selective reduction of conjoined twins at 12 weeks of gestation.

Conjoined twins occur rarely. Most of the prenatally diagnosed cases are terminated either because of extensive organ sharing or because of the presence of major structural abnormalities. We present a case of omphalopagus conjoined twins diagnosed at 10 weeks of gestation with selective reduction performed at 12 weeks. The twins were conjoined at the umbilicus with vascular communication demonstrated at the conjunction. Twin A was normal but twin B was growth restricted and hydropic. Thermocoagulation of twin B was performed at 12 weeks by passing an insulated electric wire through a 18-gauge needle placed close to the fetal heart. Reassessment at 15 weeks showed that twin A was growing normally with a small dead twin B attached at its umbilicus. Twin B was subsequently sloughed off from this attachment and could be seen lying free in the amniotic cavity at 17 weeks. Twin A was delivered at term and was healthy. A small scar could be seen just above the umbilical cord insertion. This case represents the first antenatal example of selective reduction of conjoined twins by thermocoagulation.     

Prediction of preterm delivery in twin pregnancy: a prospective, observational study of cervical length and fetal fibronectin testing.

OBJECTIVE: To evaluate prospectively cervical length measurements and fetal fibronectin detection as predictors of spontaneous preterm delivery in an unselected population of twin pregnancies. METHODS: Transvaginal ultrasound assessments of cervical length were performed serially at 18, 24, 28 and 32 weeks' gestation. Receiver-operating characteristic curves were generated at each time point to determine the optimal cut-off for cervical length and rate of change in cervical length in the prediction of preterm delivery (< 35 weeks). A bedside assay for the detection of fetal fibronectin in the maternal vaginal secretions was performed prior to cervical length measurements from 24 weeks. Likelihood ratios (LRs) were used to assess the performance of each test. RESULTS: The spontaneous preterm delivery rate was 16.5% in 91 studied twin pregnancies. A cervical length /= 2.5 mm per week between 18 and 28 weeks' gestation also predicted preterm delivery (LR+ 10.8, sensitivity 16.7%). There was no relationship between the detection of fetal fibronectin and preterm delivery. CONCLUSIONS: This study confirms the value of transvaginal ultrasound assessment of cervical length as a predictor of preterm delivery in twin pregnancies. However, the poor sensitivity of this test makes it unsuitable as a single predictor of preterm delivery. Fetal fibronectin testing does not identify twin pregnancies destined to deliver prematurely.     

Prenatal evaluation of cephalopagus conjoined twins by means of three-dimensional ultrasound at 13 weeks of pregnancy.

Cephalopagus twinning, an extremely rare type of conjoined twins, is characterized by the anterior union of the upper half of the body, with two faces each situated on the opposite side of a conjoined head. The prognosis for cephalopagus twins is extremely poor because surgical separation is not an option. Thus early prenatal diagnosis of cephalopagus twins is important to provide an opportunity for pregnancy termination if desired. However, in many instances, cephalopagus twins are misdiagnosed as a singleton pregnancy because of the extreme degree of fusion which makes accurate demonstration of the abnormalities very difficult. This report presents a case of cephalopagus twins which was confirmed at 13 weeks of gestation using three-dimensional ultrasound.     

The relevance of placental location at 20-23 gestational weeks for prediction of placenta previa at delivery: evaluation of 8650 cases.

OBJECTIVE: To determine the correlation between placental position at 20-23 weeks and incidence of birth complications caused by placental position. SUBJECTS AND METHODS: In an ongoing prospective study, placental position was determined by transabdominal sonography as part of anomaly scanning at 20-23 gestational weeks, followed by transvaginal sonography in uncertain or suspicious situations. Examination was performed in 9532 cases; feedback was obtained from 8650 patients (90.7%). RESULTS: Transabdominal sonography was followed by transvaginal scan in 363 of 8650 cases (4.2%). In 8551 cases (98.9%), we found normal placental position, with the placenta not reaching the internal os and a Cesarean section rate of 17.1% (1458/8551). The incidence of 'low placental position', with the placenta reaching the internal os was 0.66% (57/8650), with a Cesarean section rate of 21% (12/57). In 0.49% (42/8650) of cases, the placenta overlapped the internal os at 20-23 weeks; Cesarean section because of placenta previa or bleeding was performed in 28 of 8650 cases (0.32%). Vaginal delivery was possible in 43% of cases (13/30), when the overlap did not exceed 25 mm. If the overlap exceeded 25 mm (12 cases), no vaginal delivery was reported. There was no reported case of placenta previa missed at the 20-23-week scan. CONCLUSION: At 20-23 weeks, a combination of routine transabdominal and indication-based transvaginal location of placental position is a powerful tool in predicting placenta previa at delivery. The advantage of determining placental position at this stage of pregnancy is a low false-positive rate compared to at earlier stages of pregnancy. We conclude that an overlapping placenta at 20-23 weeks has the consequence of a high probability of placenta previa at delivery. An overlap of 25 mm or more at 20-23 weeks seems to be incompatible with later vaginal delivery.     

Ultrasound diagnosis of dicephalic conjoined twins at 24 weeks of gestation

We report the case of dicephalic conjoined twins discovered incidentally on a routine ultrasound at 24 weeks of gestation. There were 2 heads and a neck that fused with 1 thorax, but the spines continued all the way to the coccyx. The spines were connected medially by a fused rib, and laterally, there were ribs that went around the thorax in a more normal fashion. Antenatal ultrasound images are supplemented by postnatal photographs and x‐rays. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound, 2010     

Dynamic cervical change: is real-time sonographic cervical shortening predictive of preterm delivery in patients with symptoms of preterm labor?

OBJECTIVES: To determine prospectively if dynamic cervical change (spontaneous real-time cervical shortening) is predictive of preterm delivery at < 37 weeks' gestation in patients with symptoms of preterm labor. METHODS: This was a prospective study of patients at 23-34 weeks' gestation who were symptomatic for preterm labor. Patients underwent a 10-min real-time sonographic cervical length assessment with measurements taken at 1-min intervals. The presence or absence of dynamic cervical change, defined as real-time changes in cervical length observable to the naked eye of the sonologist during the examination, was recorded. Gestational age at delivery was obtained from medical records. Preterm delivery was defined as delivery at < 37 weeks' gestation. Dynamic cervical change and initial and minimum cervical lengths were assessed for prediction of preterm delivery. RESULTS: Seventy-six patients were enrolled, and 66 were available for outcome analysis. Thirty-one patients (47%) exhibited dynamic cervical change. Patients with dynamic change had shorter initial cervical lengths (27 mm vs. 36 mm, P = 0.001), shorter minimum cervical lengths (20 vs. 33 mm, P < 0.001) and larger changes in cervical length during the examination period (10 vs. 4 mm, P < 0.001). In the subgroup of patients with an initial cervical length > 30 mm, those with dynamic change delivered earlier than did those without dynamic change (36.8 vs. 38.6 weeks, P = 0.02), and a higher percentage delivered preterm (27% vs. 11%, odds ratio (OR), 3.0 (0.5-17.0)). Multivariate analysis showed that minimum cervical length was a better predictor of preterm delivery than was initial cervical length. CONCLUSIONS: Dynamic cervical change occurs frequently in association with shortened cervical length. In patients with longer initial cervical lengths, dynamic change may increase the risk for preterm delivery. When dynamic change is noted in a patient with preterm labor symptoms, use of the minimum cervical length observed may be better compared with initial cervical length for determining preterm delivery risk.     

Diagnosis of conjoined twins at 10 weeks using three-dimensional ultrasound: a case report.

A case report is presented of the prenatal diagnosis of conjoined twins at 10 weeks and 2 days' gestation using three-dimensional ultrasound (3D US). The multiplanar display coupled with 3D US surface rendering clearly confirmed the presence of craniopagus. The twins were facing in opposite directions with the left occipital region of one embryo fused with the left parietal-temporal region of the other. Additional multiplanar analysis above the level of the biparietal diameter demonstrated brain sharing.     

Early prediction of preterm delivery by transvaginal ultrasonography.

The clinical value of transvaginal ultrasonography in the evaluation of the uterine cervix of pregnant women was studied. Comparison with conventional transabdominal ultrasound in 24 pregnant subjects revealed that transvaginal ultrasound was superior, because the transabdominal technique usually requires a full bladder, which causes deformation and elongation of the cervix. Digital examination showed dilatation of the internal os in only ten (38.5%) of 26 patients in whom it had previously been shown by transvaginal sonography. Transvaginal ultrasonography has the advantage of providing natural and objective information on the cervix. The values of three sonographic signs found transvaginally for predicting preterm delivery were evaluated in a total of 130 at-risk patients and 129 control subjects. Shortening of the cervical length by -1.5 SD or more was associated with an increased risk of preterm delivery (11.3% vs. 2.8%, p < 0.01). A dilated internal os of more than 5 mm before 30 weeks of gestation was associated with preterm delivery more often than an undilated internal os (33.3% vs. 3.5%, p < 0.01). Dynamic changes in the degree of dilatation of the cervical canal which were found in nine women were significantly related with preterm delivery (p < 0.05). But, in the at-risk group, only dilatation of the internal os had a predictive value for preterm birth. From these data, dilatation of the internal os on transvaginal ultrasonography was proved to be an early and important predictor of preterm delivery.     

Prediction of patient-specific risk of early preterm delivery using maternal history and sonographic measurement of cervical length: a population-based prospective study.

OBJECTIVE: To develop a model for calculating the patient-specific risk of spontaneous early preterm delivery by combining maternal factors and the transvaginal sonographic measurement of cervical length at 22 + 0 to 24 + 6 weeks, and to compare the detection rate of this method to that achieved from screening by cervical length or maternal characteristics alone. METHODS: This was a population-based prospective multicenter study involving 40,995 unselected women with singleton pregnancies attending for routine hospital antenatal care in London, UK. Complete follow-up was obtained from 39,284 (95.8%) cases. The main outcomes were detection rate, false-positive rate and accuracy of predicting spontaneous delivery before 32 weeks' gestation. RESULTS: Spontaneous delivery before 32 weeks occurred in 235 (0.6%) cases. The detection rate of screening for early preterm delivery, at a fixed false-positive rate of 10%, was 38% for maternal factors, 55% for cervical length and 69% for combined testing. There was good agreement between the model estimates and the observed probabilities of preterm delivery. CONCLUSIONS: This study provides a model that can give an accurate patient-specific risk of preterm delivery. The detection rate of screening by a combination of maternal factors and the measurement of cervical length was substantially higher than that of screening by each method alone.