Factors Associated with Trial of Labour and Mode of Delivery in Robson Group 5: A Select Group of Women With Previous Caesarean Section

OBJECTIVE

To determine the proportion of women in Robson group 5 (RG5) who were eligible for a trial of labour after Caesarean (TOLAC) and, among eligible candidates, identify determinants of having a TOLAC and subsequent vaginal delivery (VD).

METHODS

This population-based cohort study used data derived from the Nova Scotia Atlee Perinatal Database. Deliveries from 1998-2014 to women in RG5 (≥1 previous CS with a singleton term cephalic fetus) were included. Eligibility for a TOLAC was based on SOGC criteria. Multivariable logistic regression was used to identify characteristics independently associated with TOLAC and VD. The characteristics associated with VD were used in a logistic model to predict the theoretical probability of VD in women who did not have a TOLAC.

RESULTS

Of the 15 111 deliveries in RG5, 75.3% were by CS. Of the 14 763 eligible women, 5488 (37.2%) had a TOLAC, of which 3739 (68.1%) resulted in VD. Predictors of VD included high area-level income and either a CS without labour or a spontaneous VD in the preceding pregnancy. While mode of previous delivery also predicted TOLAC among eligible women, high area-level income was associated with reduced odds of TOLAC. The probability of VD in women who did not undergo TOLAC was estimated to be 47.1%, and the lowest CS rate attainable in RG5 was estimated at 46.3%.

CONCLUSIONS

Sociodemographic factors such as income and previous mode of delivery were associated with the rates of TOLAC and subsequent VD in eligible women, and suggest that the Caesarean section rate in RG5 could be safely reduced.

Incidence and Carrier Frequency of CFTR Gene Mutations in Pregnancies With Echogenic Bowel in Nova Scotia and Prince Edward Island

OBJECTIVE

Fetal echogenic bowel (echogenic bowel) is associated with cystic fibrosis (CF), with a reported incidence ranging from 1% to 13%. Prenatal testing for CF in the setting of echogenic bowel can be done by screening parental or fetal samples for pathogenic CFTR variants. If only one pathogenic variant is identified, sequencing of the CFTR gene can be undertaken, to identify a second pathogenic variant not covered in the standard screening panel. Full gene sequencing, however, also introduces the potential to identify variants of uncertain significance (VUSs) that can create counselling challenges and cause parental anxiety. To provide accurate counselling for families in the study population, the incidence of CF associated with echogenic bowel and the carrier frequency of CFTR variants were investigated.

METHODS

All pregnancies for which CF testing was undertaken for the indication of echogenic bowel (from Nova Scotia and Prince Edward Island) were identified (January 2007-July 2017). The CFTR screening and sequencing results were reviewed, and fetal outcomes related to CF were assessed.

RESULTS

A total of 463 pregnancies with echogenic bowel were tested. Four were confirmed to be affected with CF, giving an incidence of 0.9% in this cohort. The carrier frequency of CF among all parents in the cohort was 5.0% (1 in 20); however, when excluding parents of affected fetuses, the carrier frequency for the population was estimated at 4.1% (1 in 25). CFTR gene sequencing identified an additional VUS in two samples.

CONCLUSION

The incidence of CF in pregnancies with echogenic bowel in Nova Scotia and Prince Edward Island is 0.9%, with an estimated population carrier frequency of 4.1%. These results provide the basis for improved counselling to assess the risk of CF in the pregnancy, after parental carrier screening, using Bayesian probability. Counselling regarding VUSs should be undertaken before gene sequencing.

Association Between Factor V Leiden Mutation, Small for Gestational Age, and Preterm Birth: A Systematic Review and Meta-Analysis

OBJECTIVE

To estimate the association of a maternal factor V Leiden (FVL) mutation with SGA and preterm birth.

DATA SOURCES

We performed a search of PubMed, Embase, Scopus, CINAHL, and the Cochrane Library from inception to April 2016 for cohort and case-control studies of women with FVL mutation and associated outcomes of SGA and preterm birth that included a reference group without FVL mutation. Additional studies were identified from reference lists of relevant research and review articles.

STUDY SELECTION

Two authors (JKB, AMO) independently examined the abstracts of the potentially eligible studies, and full texts of eligible studies were retrieved for further evaluation. Disagreements were resolved by consensus. We identified 42 studies suitable for inclusion in the meta-analysis.

DATA EXTRACTION

Thirty-two studies evaluated SGA, and 18 studies assessed preterm birth. Study quality was assessed using the Newcastle Ottawa Scale. A random effects model with inverse variance weighting was used to calculate pooled ORs and 95% CIs. Subgroup analyses were performed by study design.

DATA SYNTHESIS

The overall OR associating FVL mutation with SGA was significant (OR 1.40, 95% CI 1.18 to 1.67). Analysis of 13 cohort studies resulted in an OR of 1.20 (95% CI 1.03 to 1.41), and data from 19 case-control studies yielded an OR of 1.86 (95% CI 1.35 to 2.56). There was no significant association between FVL mutation and preterm birth (OR 1.17, 95% CI 1.00 to 1.37) when all groups were studied, but the association was significant for case-control studies alone (OR 1.40, 95% CI 1.05 to 1.86).

CONCLUSION

There is an increased risk for SGA in pregnancies complicated by FVL mutation in both cohort and case-control study designs. The risk of preterm birth with FVL mutation is less clear, although there is conflicting evidence from cohort and case-control studies regarding the risk of preterm birth associated with FVL mutation.

Adverse Perinatal Conditions Associated With Prenatally Detected Fetal Echogenic Bowel in Nova Scotia

OBJECTIVE

This study sought to estimate the association of adverse perinatal outcomes with pregnancies complicated by fetal echogenic bowel.

METHODS

Data for pregnancies complicated with echogenic bowel identified in the second trimester were derived from the tertiary referral IWK Health Centre (Halifax, NS) Viewpoint Ultrasound Database augmented by medical chart review. The study was undertaken between 2003 and 2014. Rates of positive cytomegalovirus and toxoplasmosis infection were determined using maternal serology and amniocentesis results. Rates of intrauterine growth restriction, abnormal karyotype, cystic fibrosis, antenatal bleeding, and bowel abnormalities were also determined. Neonatal information included newborn urine culture results and postnatal genetic testing. Univariate analyses compared rates of infection with isolated echogenic bowel and echogenic bowel with other ultrasound findings, with statistical significance set at P <0.05.

RESULTS

There were 422 pregnancies identified prenatally with echogenic bowel (82% had isolated echogenic bowel). Of these, 92 (22%) had at least one of the foregoing associated abnormalities. Three percent of women had serologic test results positive for cytomegalovirus or toxoplasmosis, with <1% documented newborn infections. Cystic fibrosis and other genetic diagnoses were observed in 8%, intrauterine growth restriction in 14%, antenatal bleeding in 19%, and bowel abnormalities in 3% of the cases of echogenic bowel. Pregnancies with isolated echogenic bowel had an 80% reduction in risk for these significant outcomes, in contrast to a four- to 11-fold increased risk of specific outcomes when additional ultrasound findings were present.

CONCLUSION

An overall rate of adverse conditions of 22% with prenatally detected echogenic bowel serves to inform women and health care providers and emphasizes the importance of careful screening fetal ultrasound studies and timely referral for comprehensive assessment with findings of echogenic bowel for evaluation for associated findings.