Outcomes in twin pregnancies reduced to singleton pregnancies compared with ongoing twin pregnancies.

OBJECTIVE: Multifetal pregnancy reduction has been shown to improve outcomes in triplet and higher-order multiple pregnancies. The data for fetal reduction of twin pregnancies are limited. The purpose of this study was to compare adverse pregnancy outcomes in ongoing twin pregnancies compared with twin pregnancies reduced to singletons. STUDY DESIGN: This was a retrospective cohort study comparing dichorionic diamniotic twin pregnancies with dichorionic diamniotic twin pregnancies reduced to singleton gestations between 11 and 24 weeks' gestation in a single maternal-fetal medicine practice over a 9 year period. Adverse pregnancy outcomes after 24 weeks were compared, with a value of P < .05 used for significance. RESULTS: Five hundred one ongoing twin pregnancies and 63 twin pregnancies reduced to singletons were included. Patients with reductions to singletons had a significantly lower risk of preterm delivery before 37 weeks' gestation (10% vs 43%; P < .001) but no difference in the risk of preterm delivery before 34 weeks' or 28 weeks' gestation. Patients with reductions to singletons also had a lower risk of infant birthweight less than the 10% (23% vs 49%; P < .001) but no difference in the risk of infant birthweight less than the 5%. There was no difference in the risk of fetal demise after 24 weeks' gestation. CONCLUSION: Fetal reduction of twin pregnancies decreases the risk of late preterm birth and birthweight less than the 10% but not the risks of more severe complications such as early preterm birth or birthweight less than the 5%.

Risk factors for cesarean delivery in twin pregnancies attempting vaginal delivery.

OBJECTIVE: The purpose of this study was to estimate independent risk factors for cesarean delivery in patients with twin pregnancies who attempt vaginal delivery. STUDY DESIGN: This was an historic cohort of twin pregnancies that were delivered in 1 practice from June 2005 to February 2014. Baseline characteristics were compared between women who delivered vaginally and women who underwent cesarean delivery in labor. Logistic regression analysis was performed to estimate independent risk factors for cesarean delivery. RESULTS: Two hundred eighty-six women with twin pregnancies who had attempted vaginal delivery were included in the study. The overall modes of delivery were vaginal delivery (82.2%), cesarean delivery (17.8%), and combined vaginal-cesarean delivery (0%). The most common indication for cesarean delivery in labor was an arrest disorder (82.4%). The risk factors that were associated independently with cesarean delivery were nulliparity (adjusted odds ratio, 5.78; 95% confidence interval, 2.24-14.88) and advanced maternal age of ≥35 years (adjusted odds ratio, 2.36; 95% confidence interval, 1.16-4.80). The patients at highest risk for cesarean delivery (nulliparous, advanced maternal age, induced labor) still had a 48.6% likelihood of vaginal delivery. CONCLUSION: In patients with twin pregnancies who attempt labor, nulliparity and advanced maternal age are associated independently with cesarean delivery in labor. However, even the patients at highest risk for cesarean delivery have nearly a 50% likelihood of successful vaginal delivery and therefore should be allowed to attempt vaginal delivery if it is desired and not otherwise contraindicated.

Antenatal Surveillance in Twin Pregnancies Using the Biophysical Profile.

Objectives-The nonstress test is currently the most widely used modality for antenatal surveillance in twin pregnancies, with a quoted false-positive rate of 11%-12%. Our objective was to report our experience with the sonographic portion of the biophysical profile in twin pregnancies as the primary screening modality.Methods-Women with twin pregnancies delivered by a single maternal-fetal medicine practice from 2005 to 2013 were included. We excluded monoamniotic twins. Twin pregnancies began weekly sonography for the biophysical profile starting at 32 to 33 weeks, or earlier if indicated. The nonstress test was performed if the sonographic biophysical profile score was less than 8 of 8. We reviewed biophysical profile scores and outcomes for all patients who delivered at 33 weeks or later to assess the false-positive rate for the biophysical profile, as well as the incidence of intrauterine fetal death (IUFD) after initiation of antenatal surveillance.Results-A total of 539 twin pregnancies were included. The incidence of IUFD per patient was 2 per 539 (0.4%; 95% confidence interval [CI], 0.1%-1.3%), and the incidence of IUFD per fetus was 2 per 1078 (0.19%; 95% CI, 0.05%-0.7%). The overall positive screen rate was 24 per 539 (4.45%; 95% CI, 3.0%-6.5%). The false-positive screen rate, defined as an abnormal biophysical profile that did not diagnose an IUFD or lead to delivery, was 10 per 539 (1.9%; 95% CI, 1.0%-3.4%).Conclusions-In twin pregnancies the use of the sonographic biophysical profile for routine antenatal surveillance has a low false-positive rate, with a very low incidence of IUFD. The sonographic biophysical profile should be considered as a primary mode for antenatal surveillance in twin pregnancies, with a reflex nonstress test for an abnormal score.

Gestational age at cervical length and fetal fibronectin assessment and the incidence of spontaneous preterm birth in twins.

OBJECTIVES: To estimate the risk of spontaneous preterm birth in twin pregnancies based on transvaginal sonographic cervical length, fetal fibronectin (fFN) testing, and the gestational age at which these tests were performed. METHODS: Women with twin pregnancies, cervical length assessment, and fFN testing between 22 weeks and 31 weeks 6 days in a single maternal-fetal medicine practice from 2005 to 2013 were included. All testing was done on asymptomatic women on an out-patient basis. Women with monochorionic monoamniotic twins and twin-twin transfusion were excluded. Logistic regression analysis was used to estimate the risk of spontaneous preterm birth before 35, 32, and 28 weeks. RESULTS: Six hundred eleven patients were included and underwent a total of 2406 cervical length measurements and 2279 fFN tests over the course of the study period. The likelihood values for spontaneous preterm birth before 35, 32, and 28 weeks were 19.1%, 6.3%, and 2.3%, respectively. The risk of spontaneous preterm birth before 35 weeks increased with a decreasing cervical length (coefficient for the log of the odds ratio [OR coefficient], -0.13; P < .01; 95% confidence interval [CI], -0.22 to -0.037), a positive fFN result (OR coefficient, 1.04; P < .01; 95% CI, 0.45 to 1.64), as well as earlier gestational ages at testing (OR coefficient, -0.214; P < .01; 95% CI, -0.33 to -0.10). Similar results were seen for spontaneous preterm birth before 32 and 28 weeks. CONCLUSIONS: In asymptomatic patients with twin pregnancies, the cervical length, fFN, and gestational age are all significantly associated with spontaneous preterm birth.

Abnormal Biochemical Analytes Used for Aneuploidy Screening and Adverse Pregnancy Outcomes in Twin Gestations.

OBJECTIVE: The objective of this study was to determine if first- and second-trimester biochemical markers for aneuploidy have an association with adverse pregnancy outcomes in twin gestations. STUDY DESIGN: A retrospective cohort study of patients who presented with dichorionic diamniotic twin gestations was performed. Patients with first-trimester low pregnancy-associated plasma protein A (PAPP-A) or low free ß human chorionic gonadotropin (ß-hCG), or second-trimester elevated α-fetoprotein (AFP), elevated inhibin A, elevated hCG, or low unconjugated estradiol were identified. The rates of adverse pregnancy outcomes were compared between patients with or without abnormal analytes with p < 0.05 used as significance. RESULTS: In this study, 340 pregnancies were included. Patients with a low PAPP-A had an increased risk for delivery < 37 weeks. Patients with an elevated second-trimester hCG had an increased risk for spontaneous delivery < 28 weeks and neonatal intensive care unit (NICU) admission. Patients with an elevated inhibin A had an increased risk of spontaneous delivery at < 37 and NICU admission. Patients with an elevated AFP had an increased risk of a NICU admission. CONCLUSION: Certain abnormal aneuploidy markers are associated with an increased risk of adverse pregnancy outcomes in twin gestations.

Is MSAFP still a useful test for detecting open neural tube defects and ventral wall defects in the era of first-trimester and early second-trimester fetal anatomical ultrasounds?

INTRODUCTION: To evaluate whether maternal serum α-fetoprotein (MSAFP) improves the detection rate for open neural tube defects (ONTDs) and ventral wall defects (VWD) in patients undergoing first-trimester and early second-trimester fetal anatomical survey. MATERIAL AND METHODS: A cohort of women undergoing screening between 2005 and 2012 was identified. All patients were offered an ultrasound at between 11 weeks and 13 weeks and 6 days of gestational age for nuchal translucency/fetal anatomy followed by an early second-trimester ultrasound at between 15 weeks and 17 weeks and 6 days of gestational age for fetal anatomy and MSAFP screening. All cases of ONTD and VWD were identified via query of billing and reporting software. Sensitivity and specificity for detection of ONTD/VWD were calculated, and groups were compared using the Fisher exact test, with p < 0.05 as significance. RESULTS: A total of 23,790 women met the criteria for inclusion. Overall, 15 cases of ONTD and 17 cases of VWD were identified; 100% of cases were diagnosed by ultrasound prior to 18 weeks' gestation; none were diagnosed via MSAFP screening (p < 0.001). First-trimester and early second-trimester ultrasound had 100% sensitivity and 100% specificity for diagnosing ONTD/VWD. DISCUSSION: Ultrasound for fetal anatomy during the first and early second trimester detected 100% of ONTD/VWD in our population. MSAFP is not useful as a screening tool for ONTD and VWD in the setting of this ultrasound screening protocol.

The relationship between preeclampsia and intrauterine growth restriction in twin pregnancies.

OBJECTIVE: Preeclampsia and intrauterine growth restriction (IUGR) are correlated in singleton pregnancies. The objective of this study was to estimate their relationship in twin pregnancies. STUDY DESIGN: Cohort of 578 patients with twin pregnancies delivered by 1 maternal fetal medicine practice from 2005-2013. Patients with chronic hypertension, monochorionic-monoamniotic placentation, twin-twin transfusion, and major congenital anomalies were excluded. Standard definitions were used for gestational hypertension and preeclampsia. We defined IUGR as any twin birthweight less than the 5th percentile for gestational age, as well as any twin birthweight less than the 10th percentile for gestational age. RESULTS: The incidence of preeclampsia was 14.9%, the incidence of birthweight <10% was 50.0%, and the incidence of birthweight <5% was 27.5%. Comparing patients with and without preeclampsia, the rate of birthweight <5th percentile did not differ (27.9% vs 27.4%, P = .929), nor did the rate of birthweight <10th percentile (48.8% vs 50.2%, P = .815). We had 80% power with an alpha error of 5% to show a difference in the likelihood of IUGR <10th percentile from 50% to 66% and a difference in the likelihood of IUGR <5th percentile from 27% to 42% in patients without and with preeclampsia. CONCLUSION: In patients with twin pregnancy, there is no correlation between preeclampsia and IUGR. This suggests that in twin pregnancies, as opposed to singleton pregnancies, the pathophysiology may differ between these 2 common conditions.

Screening approach for gestational diabetes in twin pregnancies.

OBJECTIVE: The objective of this study was to evaluate the ideal cutoff for the glucose challenge test (GCT) in twin pregnancies undergoing screening for gestational diabetes mellitus (GDM). STUDY DESIGN: A historical cohort of patients with twin pregnancies were identified from 1 maternal-fetal medicine practice from 2005 through 2013. All patients were administered a 1-hour, 50-g GCT between 24-28 weeks' gestation. All patients with a GCT of ≥130 mg/dL underwent a 3-hour, 100-g oral glucose tolerance test. The diagnosis of GDM was made if 2 of the 4 values on the oral glucose tolerance test were abnormal (Carpenter and Coustan). The testing characteristics of the GCT for diagnosis of GDM were evaluated using 3 selected cutoffs: ≥130, ≥135, and ≥140 mg/dL. We excluded all patients diagnosed with GDM <24 weeks. RESULTS: In all, 475 patients with twin pregnancies underwent a GCT between 24-28 weeks. The incidence of GDM was 6.5%. The positive screen rate using the 3 selected cutoffs were: ≥130 mg/dL, 34.7%; ≥135 mg/dL, 28.6%; and ≥140 mg/dL, 23.4%. A GCT cutoff of ≥135 mg/dL maintained 100% sensitivity, with a specificity of 76.4%. Using this cutoff, the positive predictive value was 22.8% and the negative predictive value was 100%. Compared to a cutoff of ≥130 mg/dL, a cutoff of ≥135 mg/dL resulted in 6.1% less patients testing positive while maintaining the same 100% sensitivity. CONCLUSION: In twin pregnancies, the optimal 1-hour, 50-g GCT screening cutoff appears to be ≥135 mg/dL.

Natural history of vasa previa across gestation using a screening protocol.

OBJECTIVES: The purpose of this study was to estimate the prevalence and persistence rate of vasa previa in at-risk pregnancies using a standardized screening protocol. METHODS: We conducted a descriptive study of patients with a diagnosis of vasa previa from a single ultrasound unit between June 2005 and June 2012. Vasa previa was defined as a fetal vessel within 2 cm of the internal cervical os on transvaginal sonography. Screening for vasa previa using transvaginal sonography with color flow mapping was performed routinely in the following situations: resolved placenta previa, prior pregnancy with vasa previa, velamentous insertion of the cord in the lower uterine segment, placenta succenturiata in the lower uterine segment, and twin gestations. RESULTS: A total of 27,573 patients were referred to our unit for fetal anatomic surveys over the study period. Thirty-one cases of vasa previa were identified, for an incidence of 1.1 per 1000 pregnancies. Twenty-nine cases had full records available for analysis. Five patients (17.2%) had migration and resolution of the vasa previa. When the diagnosis was made during the second trimester (<26 weeks), there was a 23.8% resolution rate (5 of 21); when the diagnosis was made in the third trimester, none resolved (0 of 8 cases). Of the 24 pregnancies (5 twin gestations and 19 singleton gestations) with persistent vasa previa, there was 100% perinatal survival and a median length of gestation of 35 weeks (range, 27 weeks 5 days-36 weeks 5 days). No known missed cases were identified over the study period. CONCLUSIONS: The use of standardized screening for vasa previa based on focused criteria was found to be effective in diagnosing vasa previa, with a 100% survival rate. Vasa previa diagnosed during the second trimester resolves in approximately 25% of cases.

Prophylactic cerclage in the management of twin pregnancies.

OBJECTIVE: To determine if prophylactic cerclage improves pregnancy outcomes in women with twin pregnancies without a history of cervical insufficiency. STUDY DESIGN: Women with twin pregnancies who received outpatient preterm labor surveillance services between January 1990 and May 2004 for ≥1 day beginning at < 28.0 weeks' gestation were identified from a database. Patients with previous preterm delivery or a diagnosis of cervical incompetence in a previous or in the index pregnancy were excluded. Twin pregnancies managed with prophylactic cerclage were compared with twin pregnancies in which cerclage was not placed. The primary outcome was incidence of preterm birth prior to 32 weeks. Groups were compared using Fisher exact and Mann-Whitney U test statistics. RESULTS: Overall, 8,218 twin pregnancies met inclusion criteria, of which 146 women (1.8%) received prophylactic cerclage. Patients who received prophylactic cerclage had a significantly higher incidence of preterm birth before 32 weeks and infants with lower mean birth weight and longer nursery stays. No significant difference was seen in mean gestational age at delivery. This study had 80% power to detect a 7% reduction in the primary outcome. CONCLUSION: Prophylactic cerclage was not associated with a lower risk of preterm birth and adverse neonatal outcomes in twin pregnancies without history of cervical insufficiency.

Persistence of placenta previa in twin gestations based on gestational age at sonographic detection.

OBJECTIVES: The purpose of this study was to evaluate the gestational age at sonographic detection of placenta previa as a predictor of previa persistence until delivery in twin gestations. METHODS: A retrospective cohort of twin pregnancies with placenta previa in a single ultrasound unit was analyzed from 2005 to 2010. Pregnancies were ascertained from a database. Diagnoses were confirmed by transvaginal imaging. Previa was categorized as complete if the placenta completely covered the internal os or marginal if the inferior placental edge reached within 2 cm. Gestational ages were grouped into intervals from 15 to 35 weeks. The study outcome was placenta previa at delivery. Only twin pregnancies at 25 weeks' gestation and later were analyzed using nonparametric statistics as appropriate, with P < .05 as significant. RESULTS: Placenta previa was detected in 120 twin pregnancies in the second trimester: 32 complete and 88 marginal. Of those with placenta previa at 15 to 19, 20 to 23, 24 to 27, 28 to 31, and 32 to 35 weeks, previa persisted until delivery in 8.3%, 19.2%, 50%, 75%, and 92.5%, respectively. Only at 15- to 19- and 20- to 23-week intervals was complete previa more likely to persist than marginal previa (P < .001). CONCLUSIONS: The likelihood of placenta previa persistence in twins is dependent on the gestational age at sonographic detection. Only at earlier gestations does the type of previa affect its persistence. As gestational age advances, the likelihood of resolution of placenta previa diminishes regardless of the type noted.

The significance of a positive fetal fibronectin in the setting of a normal cervical length in twin pregnancies.

To estimate the risk of preterm birth in asymptomatic women with twin pregnancies with a normal cervical length (CL) and a positive fetal fibronectin (fFN), we reviewed a retrospective cohort of twin pregnancies delivered in our practice from 2005 to 2010. Patients were screened from 22 to 32 weeks with CL and fFN at 2- to 4-week intervals. We examined 244 patients with twin pregnancies and a normal CL (>25 mm) between 22 and 32 weeks and compared outcomes based on the fFN result. Fourteen (5.7%) patients had a positive fFN and 230 (94.3%) patients had a negative fFN. Positive fFN was associated with an increased the risk of spontaneous preterm birth < 37 weeks (85.7% versus 38.3%, p = 0.001), < 35 weeks (50% versus 11.8%, p < 0.001), < 34 weeks (35.7% versus 6.9%, p < 0.001), and < 32 weeks (21.4% versus 2.2%, p < 0.001). On adjusted analysis, a positive fFN was independently associated with preterm birth < 32 weeks (odds ratio 6.8, 95% confidence interval 1.42, 32.2) and gestational age at delivery (p = 0.001). In the setting of a normal CL, a positive fFN is significantly associated with preterm birth in asymptomatic twin pregnancies. Contingency model screening of fFN in asymptomatic twin pregnancies solely based on CL evaluation may fail to identify a cohort of at-risk patients.

Women with preterm premature rupture of the membranes do not benefit from weekly progesterone.

OBJECTIVE: We sought to determine if 17-alpha-hydroxyprogesterone (17P) extends gestation vs placebo in women with preterm premature rupture of the membranes (PPROM). STUDY DESIGN: Women with vertex presentations with PPROM, 20-30 weeks' gestation, were randomized to receive weekly 17P or placebo in an attempt to prolong the pregnancy. A total of 69 patients (17P, n = 33; placebo, n = 36) were randomized into this study. RESULTS: Initial cervical dilatation, gestational age at enrollment, and interval to delivery were not different between the 2 groups (P = .914, .424, and .146, respectively). Time of randomization to delivery (P = .250), mode of delivery (relative risk, 1.16; 95% confidence interval, 0.66-2.06), and the neonatal outcome statistics of morbidity (P = .820) and mortality (relative risk, 1.28; 95% confidence interval, 0.59-2.75) were similar between the 2 groups. CONCLUSION: In patients with PPROM, 17P did not extend gestation vs placebo and cannot be recommended for treatment in such women.

Second-trimester estimated fetal weight and discordance in twin pregnancies: association with fetal growth restriction.

OBJECTIVES: The purpose of this study was to estimate the association between second-trimester estimated fetal weight and fetal growth restriction in twin pregnancies. METHODS: A historical cohort of 306 twin pregnancies from a single center was analyzed. Estimated fetal weight and discordance at 18 to 24 weeks were calculated. Patients with a fetus whose second-trimester estimated fetal weight was below the 10th percentile were compared to patients with both fetuses at or above the 10th percentile. Also, patients with second-trimester discordance of 15% or greater were compared to patients with discordance of less than 15%. RESULTS: Second-trimester discordance was significantly smaller than birth weight discordance (mean discordance ± SD, 7.41% ± 6.06% versus 11.43% ± 9.6%, respectively; P < .001). Patients with second-trimester discordance of 15% or greater were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (67.7% versus 44.1%; P = .012) and below the 5th percentile for gestational age (41.9% versus 22.8%; P = .019). Patients with a second-trimester estimated fetal weight below the 10th percentile were significantly more likely to deliver a twin with a birth weight below the 10th percentile for gestational age (65.5% versus 44.5%; P = .031) and below the 5th percentile for gestational age (55.2% versus 21.5%; P < .001). CONCLUSIONS: In twin pregnancies, second-trimester estimated fetal weight below the 10th percentile and discordance of 15% or greater are associated with fetal growth restriction.

Intrauterine growth restriction in twin pregnancies: incidence and associated risk factors.

We sought to estimate the association of several maternal risk factors with intrauterine growth restriction (IUGR) in twin pregnancies. This is a case-control study of 313 patients with twin pregnancies delivered greater than 24 weeks between June 2005 and January 2010. We used three definitions of IUGR: (1) either twin with a birth weight < 10th percentile for gestational age; (2) either twin with a birth weight < 5th percentile for gestational age; and (3) birth-weight discordance ≥ 20%. Using each definition of IUGR, we estimated the association between IUGR and maternal age, weight, monochorionicity, in vitro fertilization, pregnancy reduction, thrombophilia, hypertension, and diabetes. Overall, 47% of patients delivered at least one twin with a birth weight <10th percentile, 27% of patients delivered at least one twin with a birth weight <5th percentile, and 16% of patients had birth-weight discordance of ≥20%. Using any of these three definitions for IUGR in twin pregnancies, there was no significant association between IUGR and any of the risk factors examined. This remained true when we excluded all patients who delivered <34 weeks. IUGR is very common in twin pregnancies. However, in twin pregnancies, IUGR cannot be predicted by maternal risk factors.

First-trimester aneuploidy risk assessment: the impact of comprehensive counseling and same-day results on patient satisfaction, anxiety, and knowledge.

We evaluated the added benefit of a comprehensive counseling protocol for first-trimester aneuploidy risk assessment. We performed a prospective cohort study surveying patients referred for first-trimester aneuploidy risk assessment. We compared responses between women who underwent serum testing done in advance of their ultrasound such that their final risk assessment was given to them the same day as their ultrasound (comprehensive) versus women who underwent serum testing the same day as their ultrasound and who therefore received their final risk assessment later (standard). Response rate was 94.8%. The comprehensive group was significantly more likely to receive counseling in accordance with recommended American College of Obstetricians and Gynecologists (ACOG) guidelines, had significantly greater reduction in anxiety and increased satisfaction, and was more likely to report an increased understanding of their results. The comprehensive group scored significantly higher on test-style questions about aneuploidy risk assessment. Comprehensive aneuploidy risk assessment counseling including same-day results is associated with increased patient understanding and satisfaction, decreased anxiety, and increased adherence to ACOG guidelines.

Treatment of severe nausea and vomiting of pregnancy with subcutaneous medications.

We examined treatment outcomes in women with severe nausea and vomiting of pregnancy (NVP) receiving outpatient nursing support and either subcutaneous metoclopramide or subcutaneous ondansetron via a microinfusion pump. Among women receiving outpatient nursing services, we identified those diagnosed with severe NVP having a Pregnancy-Unique Quantification of Emesis (PUQE) score of greater than 12 at enrollment and prescribed either metoclopramide (N = 355) or ondansetron (N = 521) by their physician. Maternal characteristics, response to treatment, and start versus stop values were compared between the medication groups. Allocation to group was based on intention-to-treat protocol. Maternal characteristics were similar between the groups. Days to reduction in PUQE score levels were similar (median 2 days, metoclopramide; 3 days, ondansetron; P = 0.206). Alteration from metoclopramide to ondansetron (31.8%) was more frequent than alteration from ondansetron to metoclopramide (4.4%; P < 0.001). Improvement of NVP symptoms and reduced need for hospitalization was noted with both medications. Treatment with either metoclopramide or ondansetron resulted in significant improvement of NVP symptoms with half of women showing a reduction from severe symptoms to moderate or mild symptoms within 3 days of treatment initiation. Alteration in treatment was significantly greater in patients initially prescribed metoclopramide.

Prediction of spontaneous preterm birth in asymptomatic twin pregnancies using the change in cervical length over time.

OBJECTIVE: We sought to evaluate the change in cervical length (CL) as a predictor of preterm birth in asymptomatic twin pregnancies. STUDY DESIGN: We studied a historical cohort of 121 twin pregnancies with CL testing between 18-24 weeks who had a follow-up CL 2-6 weeks after the initial CL. RESULTS: A total of 19 patients had their CL decrease by > or = 20% (shortened CL group) and 102 patients' CL decreased by less, or not at all (stable CL group). The shortened CL group had a significantly higher rate of spontaneous preterm birth <28 weeks, <30 weeks, <32 weeks, and <34 weeks. This remained true even when excluding patients with a short CL (< or = 25 mm) on the repeated CL. CONCLUSION: In twin pregnancies, a CL that decreases by 20% over 2 measurements is a significant predictor of very preterm birth, even in the setting of a normal CL. Serial CL measurements should be considered in twin pregnancies, starting <24 weeks.

Association between second-trimester cervical length and spontaneous preterm birth in twin pregnancies.

OBJECTIVE: The purpose of this study was to define normal second-trimester cervical length (CL) measurements and to estimate the association between second-trimester CL and spontaneous preterm birth (SPTB) in twin pregnancies. METHODS: A retrospective cohort of 309 asymptomatic patients with twin pregnancies who had routine outpatient CL assessment in the second trimester was studied. We looked at the gestational age periods of 16 to 17 6/7, 18 to 19 6/7, 20 to 21 6/7, and 22 to 23 6/7 weeks. We estimated the association between the CL measurement during each period and SPTB. A short CL was defined both as a CL at or below the 10th percentile for gestational age and 25 mm or less. We also performed regression analyses controlling for a number of clinically important factors: maternal age, chorionicity, in vitro fertilization, multifetal reduction, prior term births, prior preterm births, prepregnancy body mass index, and cerclage. RESULTS: The CL measurement at 16 to 17 6/7 weeks was not associated with gestational age at delivery or SPTB. At 18 to 19 6/7 and 20 to 21 6/7 weeks, the CL measurement was not significantly associated with gestational age at delivery or SPTB before 28 and 32 weeks. There was an association with SPTB before 35 weeks. At 22 to 23 6/7 weeks, the CL measurement had a significant association with gestational age at delivery and SPTB before 28, 32, and 35 weeks (P < .05). A short CL at 22 to 23 6/7 weeks was significantly associated with SPTB before 32 and 35 weeks (P < .05). CONCLUSIONS: In second-trimester twin pregnancies, the strongest association between CL and SPTB is at 22 to 23 6/7 weeks.

Prediction of spontaneous preterm birth in asymptomatic twin pregnancies with the use of combined fetal fibronectin and cervical length.

OBJECTIVE: The purpose of this study was to evaluate combined fetal fibronectin (fFN) test result and cervical length (CL) as predictors of spontaneous preterm birth in asymptomatic twin pregnancies. STUDY DESIGN: We examined a retrospective cohort of 155 twin pregnancies with combined fFN and CL testing between 22 and 32 weeks gestation. RESULTS: A positive fFN test result at 22-32 weeks or a CL <20 mm increased the risk of spontaneous preterm birth at <37, <34, <32, <30, and <28 weeks' gestation. The combination of a positive fFN test result and CL<20 mm had a significantly higher positive predictive value for delivery at all gestational ages than either positive test alone. On adjusted analysis, a positive fFN test result was a stronger predictor of spontaneous preterm birth than a short CL. CONCLUSION: In asymptomatic twin pregnancies, fFN and CL testing between 22 and 32 weeks gestation can identify pregnancies that are at significantly increased risk for preterm birth, including deliveries at <28 weeks' gestation.