The effect of cerclage in twin gestations with short cervix: a Bayesian evaluation

Objective: Bayesian inference allows the revision of prior clinical estimates of treatment effectiveness based on current data. We apply it to a published dataset evaluating the effect of cerclage upon preterm delivery in twin gestations with a short cervix.

Study design: Prior probability distributions for delivery <35 weeks gestation for the control group and the treatment (cerclage) group were constructed under assumptions ranging from treatment having no effect (prior A) to halving early deliveries (prior C). Likelihood functions were calculated based on a published meta-analysis. Posterior probability densities were derived from which risk ratios for early delivery were computed, with 95% credible intervals and the probability of cerclage benefit.

Results: Median posterior risk ratios (95% credible intervals) for delivery <35 weeks with cerclage are 1.51 (1.02–2.33) for prior A and 1.11 (0.72–1.77) for prior C. The probability of cerclage benefit ranged from 2.1% for prior A to 31.4% for prior C. By comparison, the conventional risk ratio (95% confidence interval) for early delivery, based on the data alone, is 2.08 (1.18–3.69).

Conclusions: As might be anticipated, those with low expectation of cerclage benefit remain more convinced of the ineffectiveness (or harm) of the procedure than those with higher expectations.     

First-trimester risk assessment: twin gestations

OBJECTIVE: To determine the role of first-trimester screening in multiple gestations. MATERIALS AND METHODS: A review of the literature revealed numerous studies in this area. However, most of the studies involved first-trimester singleton pregnancies. RESULTS: The few studies that reviewed the experience with multiple gestations demonstrated feasibility of this technique. However, the detection rate for twin gestations was less than that of singleton gestations. CONCLUSION: Although the data support the value of screening twins with biochemistry and ultrasound in the first trimester, further study is necessary to determine the most sensitive method.     

The association between maternal height and pregnancy outcomes in twin gestations

Objective: We sought to assess the association between maternal height and the risk of preterm birth, fetal growth restriction and mode of delivery in twin gestations.

Study design: Cohort study of patients with twin pregnancies delivered from 2005 to 2014. We compared pregnancy outcomes between patients of short stature?≤159?cm to those of normal stature?≥160?cm. Patients with monoamniotic twins and major fetal anomalies were excluded. Pearson’s correlation, Chi-square and Student’s t-test were used as appropriate.

Results: Six hundred and sixty-six patients were included, 159 (23.9%) of whom had short stature (mean height 155.8?±?2.5?cm) and 507 (76.1%) of whom had normal stature (mean height 167.2?±?5.5?cm). There were no differences in outcomes between the groups in regards to preterm birth, gestational age (GA) at delivery, birth weight of either twin, preeclampsia, gestational diabetes or cesarean section rate. Results were similar when the groups were stratified by parity. As a continuous variable, maternal height did not correlate with GA at delivery (p=?0.388), cesarean delivery (p?=?0.522) nor the birth weight of the larger (p?=?0.206) or smaller (p?=?0.307) twin.

Conclusion: In twin pregnancies, maternal short stature is not associated with preterm birth, fetal growth restriction or cesarean section rate. This suggests that although anthropometric measurements have long been used to counsel patients in regards to outcomes, patients of short stature should be reassured that their height does not appear to lead to adverse twin pregnancy outcomes.     

Outcomes following rescue cerclage in twin pregnancies*

Objective: Our aim was to compare perinatal outcomes in twin pregnancies complicated by premature asymptomatic cervical dilatation treated with rescue cerclage and expectant management.

Methods: A retrospective cohort study was conducted at a single tertiary referral center between 2003 and 2014 and included all women with twins found to have a dilated cervix with intact membranes before 25-week gestation. Pregnancy outcomes were compared between women with rescue cerclage and those managed expectantly. A total of 36 women were eligible for the study, 27 (75.0%) of whom had a rescue cerclage compared to 9 (25.0%) women managed expectantly. Student’s t-test was used to compare continuous variables between the groups and the chi-square and Fisher’s exact tests were used for categorical variables as appropriate. Statistical analysis was performed with the SPSS v21.0 software (IBM Corp; Armonk, NY). Differences were considered significant when the p value was less than .05.

Results: Among the 27 women with a rescue cerclage, the mean gestational age at time of cerclage insertion was 21.5?±?2.6 weeks. The intervention and control groups were similar with respect to the degree of cervical dilatation at presentation (2.6?±?1.3 versus 3.0?±?1.5?cm, p?=?.5). Women in the cerclage group gave birth at a more advanced gestation (28.9?±?6.1 versus 24.2?±?2.6?weeks, respectively, p?=?.03) and were less likely to give birth at <34 and <28?weeks (66.7 versus 100.0%, p?=?.046, and 59.3 versus 100.0%, p?=?.02, respectively). The mean latency from the placement of cerclage to delivery was 7.3?±?5.5 weeks. Similar findings were observed when analysis was limited to women with cervical dilatation of ≤3?cm at presentation.

Conclusions: In asymptomatic women with twin pregnancies and cervical dilatation before 25?weeks of gestation, rescue cerclage can prolong pregnancy and improve perinatal outcomes when compared to expectant management.     

Antenatal factors associated with significant birth weight discordancy in twin gestations

OBJECTIVE: The purpose of this study was to evaluate factors that are associated with significant birth weight discordancy. STUDY DESIGN: As a part of an ongoing collaborative study of twins, maternal and fetal data were obtained from the medical records of twin gestations at eight medical centers. The study population was divided into groups by difference in birth weight discordancy (>or=20%, >or=25%, and >or=30%) RESULTS: Severe birth weight discordancy was associated with fetal growth deceleration by 20 to 28 weeks (adjusted odds ratio, 4.90; 95% CI, 3.15-7.64) and between 28 weeks to birth (adjusted odds ratio, 3.48; 95% CI, 1.72-7.06). Antenatal bleeding (adjusted odds ratio, 1.86; 95% CI, 1.08-3.21), preeclampsia (adjusted odds ratio, 1.70, 95% CI, 1.21-2.41), and monochorionicity (adjusted odds ratio, 2.35, 95% CI, 11.71-3.23) were also associated with birth weight discordancy. CONCLUSION: These data demonstrate the importance of the early diagnosis of placental chorionicity, because monochorionicity is associated with a 2-fold increase in birth weight discordancy in twin gestations.     

The correlation in birth timing between singleton and twin gestations in the same mother

Objective. To test the hypothesis that the timing of twin births is correlated to that of their singleton siblings.

Methods. Using the Missouri Department of Health's birth certificate database we performed a retrospective population-based cohort study of 2222 women who had at least one singleton and one twin birth (1989–1997). Pearson correlation analysis was conducted to examine the relationship in gestational age between singleton and twin births occuring in the same mother.

Results. Among 2222 mothers who had both a singleton and twin pregnancy during the study period, the mean difference in birth timing between singleton and twin siblings was 3.05 weeks (±2.9 weeks). The correlation between singleton and twin birth timing was statistically significant (r = 0.28, p < 0.001), and remained significant even after controlling for potential confounders (β = 0.459, p < 0.001).

Conclusions. We identified a significant correlation in the timing of birth between singleton and twin pregnancies in the same mother, which could be due to shared genetic, environmental, medical, social and other influences. This finding could be useful to help predict birth timing in mothers at especially high risk of preterm birth, those with a twin gestation.     

Contributions of ischaemic placental disease to preterm birth in twin gestations

Objective.?To evaluate the extent to which ischaemic placental disease (IPD) – defined as women or newborns diagnosed with pre-eclampsia, small for gestational age (SGA), or abruption, is associated with preterm birth in twin gestations.

Methods.?A population-based study of women who delivered twin live births and stillbirths at 20–44 weeks gestation from 1995–2004 in the US was performed (n?=?1,105,666). We compared the frequency of IPD in term and preterm (<37 weeks) twin births. SGA was defined as twins with birthweight <10th percentile for gestational age, and corrected for infant sex. The association between IPD and preterm birth was expressed as hazard ratio, derived from Cox proportional hazard regression models after adjusting for potential confounders.

Results.?The overall rate of twin preterm birth was 57%. IPD was present in 20% of twin preterm births in comparison to a rate of 16% at term. Both pre-eclampsia and abruption, but not SGA, were associated with increased preterm birth rates. Women with two or more of the IPD conditions were more likely to deliver at preterm than at term gestations.

Conclusion.?In comparison to twin births delivered at term, IPD is more common in preterm births. Efforts to understand the role of IPD in twin gestations based on preterm birth subtypes may reveal important insights.     

The impact of prenatal care on preterm births among twin gestations in the United States, 1989-2000

OBJECTIVE: The purpose of this study was to determine the association between prenatal care and preterm births among twin gestations in the presence and absence of high-risk pregnancy conditions. STUDY DESIGN: Twin birth data in the United States were used to determine the association between preterm birth and prenatal care with the use of logistic regression. RESULTS: Of the 779,387 twin births, 54.7% twin births were delivered preterm. The rate was higher among black women than among white women in the presence (57.0% vs 51.2%, respectively) and absence (70.3% vs 61.6%, respectively) of prenatal care. The absence of prenatal care increased the relative risk for preterm birth by 1.24-fold among black women and by 1.22-fold among white women. Lack of prenatal care was associated with increased preterm birth rates in the presence of most high-risk conditions. CONCLUSION: Prenatal care is associated with fewer twin preterm births in the presence and absence of high-risk conditions. Increased prenatal care participation may help decrease preterm birth rates and also narrow the black-white twin preterm birth disparity.     

The relationship between previous treatment for cervical dysplasia and preterm delivery in twin gestations

Abstract

Objective: To describe the impact of previous cervical surgery on preterm birth prior to 34 weeks in twins.

Methods: A retrospective review of twin pregnancies delivered between January 1998 and December 2005 at two institutions was performed. Women with a prior cold knife cone (CKC), loop electrosurgical excision procedure (LEEP), or ablative procedure were compared to a control group of women who had not undergone a previous treatment for cervical dysplasia. The primary outcome was delivery before 34 weeks of gestation.

Results: A total of 876 women met inclusion criteria. Of these, 110 (12.6%) had previous surgical procedures for cervical dysplasia, including CKC (n?=?10), LEEP (n?=?36), cryotherapy (n?=?59) and CO₂ laser treatment (n?=?5). Delivery prior to 34 weeks was more common in women with a previous CKC compared to women with no prior treatment (40% versus 11.3%; odds ratio [OR], 3.6; 95% confidence interval [CI], 1.7–8.0). Delivery prior to 34 weeks was not more common in women with a previous LEEP (8.3%; OR, 0.8; 95% CI, 0.3–2.3) or ablative procedure (9.4%; OR, 0.9; 95% CI, 0.4–1.9) in comparison to the untreated group. Adjusting for the potential confounders of age, tobacco use, infertility treatments and previous preterm birth did not change the results.

Conclusions: Previous CKC is associated with delivery prior to 34 weeks while LEEP and ablative procedures are not. CKC should be carefully considered and avoided when possible in reproductive age women.     

Perinatal outcomes with intrahepatic cholestasis of pregnancy in twin pregnancies

Objective: To describe perinatal outcomes of twin pregnancies complicated by intrahepatic cholestasis of pregnancy (ICP).

Methods: We conducted a retrospective cohort study of women delivered at a large tertiary obstetric center in Shanghai, China from January 2006 to May 2014. Delivery data were abstracted from medical records of all twin gestations delivered at the hospital.

Results: A total of 129/1922(6.7%) twin and 1190/92?273 singleton (1.3%) pregnancies were complicated by ICP. An increased risk of stillbirth among twin pregnancies was observed (3.9% and 0.8% in the ICP and non-ICP groups, respectively; aOR 5.75, 95% CI 2.00–16.6). Stillbirths with ICP and twins occurred between 33 and 35 weeks gestation compared to 36–38 weeks gestation among singletons. ICP in twins was also associated with an increased risk of preterm birth (<37 weeks) with an aOR of 4.17 (95% CI 2.47–7.04) and an aOR of 1.89 (95% CI 1.26–2.85) for delivery <35 weeks. Twin pregnancies complicated by ICP also had increased meconium staining of amniotic fluid and lower birth weight.

Conclusions: Twin pregnancies with ICP have significantly increased risks of adverse perinatal outcomes including stillbirth and preterm birth. Stillbirth occurs at an earlier gestational age in twin gestation compared to singletons, suggesting that earlier scheduled delivery should be considered in these women.     

Alternative embryo transfer on day 3 or day 5 for reducing the risk of multiple gestations

Purpose: This study was carried out to reduce the possibility of high-order multiple gestations and the failure of embryo transfer by determining their replacement date based on the number and quality of 2-day embryos.Methods: All zygotes were cocultured with cumulus cells in 10 l of YS medium containing 10% human follicular fluid (hFF) for 48 or 96 hr. In period I, all embryos were transferred on day 3 (1032 cycles). In period II, the embryos were transferred on either day 3 or day 5 by determining their replacement date based on the number and quality of 2-day embryos: there were 2701 patients in whom embryos were replaced on day 3 (in the case that the number of zygotes was less than eight and the number of good-quality embryos was less than three) and 1952 patients less than 40 years old in whom embryos were replaced on day 5 (in the case that the number of zygotes was eight or more and/or the number of good-quality embryos was three or more). On the other hand, patients who were 40 years old or more were alloted to day 3 transfer cycles, regardless of the number and quality of the 2-day embryos, due to the possibility of their not producing blastocyst-stage embryos in vitro.Results: The number of embryos transferred in period II was 2.9 ± 0.6, while that in period I was 3.7 ± 0.5. The multiple pregnancy rate was significantly decreased in period II (30.7%) compared to that (49.6%) in period I, while the pregnancy and implantation rates in period II (36.1 and 16.4%, respectively) were not lower than those (34.9 and 16.1%, respectively) in period I. The rate of triplet or more gestations was significantly minimized in period II (2.3%) compared to that in period I (26.5%).Conclusions: We propose that determination of the date on which embryos should be transferred based on the number and quality of embryos on day 2 may help to maintain an acceptable pregnancy rate, while minimizing embryo transfer failure and high-order multiple gestations.     

Comparison of perinatal outcomes of selective termination in dichorionic twin pregnancies performed at different gestational ages

Objective: To determine the perinatal outcomes of selective termination in dichorionic twin pregnancies discordant for major but non-lethal fetal anomalies performed at different gestational ages.

Methods: Thirty-one dichorionic twin pregnancies that underwent selective termination for discordant major but non-lethal fetal anomalies between January 2004 and February 2015 were retrospectively reviewed. The patients were grouped into three, according to the gestational age at which selective termination of pregnancies was performed; Group 1 (15–19 weeks), Group 2 (20–24 weeks) and Group 3 (30–33 weeks). Perinatal outcomes in all the three groups were reviewed and analyzed.

Results: The overall live birth, term birth and pregnancy loss rate were 93.6%, 54.8% and 9.6%, respectively. The overall live birth rate was 66.6% in Group 1, this rate was 100% in Group 2 and Group 3 (p?=?0.01). The rate of pregnancy loss was significantly higher in Group 1 (p?=?0.01). The overall preterm delivery rate was 38.7%. While the overall preterm delivery rate was significantly higher in Group 3 (p?=?0.04), the rate of extremely and very preterm birth was significantly lower (p?=?0.03).

Conclusion: Late selective feticide performed during the third trimester of pregnancy seems to be a safe approach and can be offered as an alternative method to reduce the total pregnancy loss and extremely and early pre-term birth rates.     

The influence of mode of delivery on twin neonatal mortality in the US: variance by birth weight discordance

OBJECTIVE: The purpose of this study was to examine if neonatal mortality rates (NMR) based on birth weight discordance (BWD) differ based on mode of delivery. STUDY DESIGN: The population-based US "matched multiple birth" database (1995 to 1998) was used to examine the effect of vaginal/vaginal (VV) and cesarean/cesarean (CC) modes of delivery (MOD) on neonatal mortality (<28 days after birth). Births at <32 weeks, congenital malformations, chromosomal anomalies, and discordant MOD (vaginal/cesarean) were excluded. The association between MOD (with CC as the reference) and neonatal mortality was expressed as relative risks (RR) with 95% CI, derived from logistic regression models. RESULTS: The NMR increased with increasing degrees of BWD regardless of mode of delivery. CC was associated with decreased NMR when BWD was between 20% and 40%, but this reached significance at BWD > or =40%; VV pairs had a 1.6-fold (95% CI 1.1-2.2) increased NMR compared with CC. CONCLUSION: In twins with BWD <40%, MOD has no effect on NMR. Beyond or equal to 40% discordance, there was lower NMR with cesarean-cesarean delivery.     

Outcomes of preterm premature rupture of membranes in twin pregnancies

Objective. To describe outcomes in twin pregnancies with preterm premature rupture of membranes (PPROM).

Methods. Dichorionic twin pregnancies complicated by PPROM at <34 weeks of gestation for the period 2003 to 2006 were identified. Outcomes were obtained through chart review. The relationship between gestational age at premature rupture of membranes (PROM), latency from PROM to delivery, and infection were examined.

Results. In 49 twin pregnancies, the median gestational age at PROM was 31 weeks with a median latency between PROM and delivery of 0 days (interquartile range 0–6). Latency intervals of ≥2 and ≥7 days were achieved by 40.8% and 22.4%, respectively. PPROM at <30 weeks was associated with significantly higher rates of latency of ≥ 2 days (70.6% vs. 25.0%) and ≥7 days (47.1% vs. 9.4%). There was a significant relationship between latency and clinical and histologic signs of infection.

Conclusions. After 30 weeks, most twin pregnancies with PPROM delivered within 2 days. Infection appears to be a consequence rather than a cause of PPROM in most cases.     

Multiple gestations and late preterm (near-term) deliveries

Multiple gestations present unique challenges to the modern obstetrician. Many twin and high-order multiple pregnancies are delivered between 34 and 37 weeks' gestation either secondary to preterm labor or obstetrical complications necessitating intervention. Recognizing the increasing prevalence of multiple gestations and the impact of late preterm deliveries in modern practice, this review analyzes the impact of multiple pregnancies on perinatal outcomes, reviews the strategies to prevent preterm labor, and summarizes potential indications for late preterm delivery. In this paper, "late preterm" has been used instead of "near-term," as the former was considered more appropriate to reflect this subgroup of preterm infants in a workshop on this topic held in July 2005, organized by the National Institute of Child Health and Human Development.