No mutations found in candidate genes for dystocia

Factors contributing to the decision to perform a cesarean section in Labrador retrievers

BACKGROUND

In the past 10 years, the frequency of unplanned cesarean sections in the Labrador Retriever breeding colony at Guiding Eyes for the Blind stayed around 10% (range 5% to 28%). To reduce the number of cesarean sections, factors influencing the occurrence of a cesarean section need to be known. The goal of this study was to identify factors that contribute to the decision to perform a cesarean section.

RESULTS

Of the 688 Labrador Retriever litters whelped between 2003 and 2016, 667 litters had sufficient data and remained in the analysis. The target trait was ordinal with the three levels "normal whelping", "assisted whelping" and "cesarean section". A general ordinal logistic regression approach was used to analyze the data. Model selection with possible predictors resulted in a final model including weight of the dam, the weight of the heaviest puppy of a litter, the number of fetuses malpositioned and the quality of uterine contractions. Weight and size of a litter, parity, maternal inbreeding coefficient, whelping season, dam and sire were dropped from the model because they were not significant. The risk of a cesarean section was influenced by the combination of the weight of the dam and the weight of the heaviest puppy in the litter, as well as by the number of malpositioned fetuses and the quality of the contractions. Larger puppies increased the risk of cesarean section especially when the dam had a lighter weight. For dams weighing 23.6 kg and 32.8 kg the predicted probability of a cesarean section was low, with 0.06 and 0.02, respectively, when the heaviest puppy in a litter was light (0.42 kg), contractions were normal and no fetus was malpositioned. However, the probability of a cesarean section was much higher, ranging from 0.24 to 0.08, when the heaviest puppy in a litter was heavy (0.66 kg).

CONCLUSIONS

Means to reduce the cesarean section frequency in this Labrador Retriever breeding colony should include genetic selection for ideal puppy weight. In addition, dams with an adult body weight substantially below average should not be selected as breeders in this colony.

Identification of a myometrial molecular profile for dystocic labor

Background

The most common indication for cesarean section (CS) in nulliparous women is dystocia secondary to ineffective myometrial contractility. The aim of this study was to identify a molecular profile in myometrium associated with dystocic labor.

Methods

Myometrial biopsies were obtained from the upper incisional margins of nulliparous women undergoing lower segment CS for dystocia (n = 4) and control women undergoing CS in the second stage who had demonstrated efficient uterine action during the first stage of labor (n = 4). All patients were in spontaneous (non-induced) labor and had received intrapartum oxytocin to accelerate labor. RNA was extracted from biopsies and hybridized to Affymetrix HuGene U133A Plus 2 microarrays. Internal validation was performed using quantitative SYBR Green Real-Time PCR.

Results

Seventy genes were differentially expressed between the two groups. 58 genes were down-regulated in the dystocia group. Gene ontology analysis revealed 12 of the 58 down-regulated genes were involved in the immune response. These included (ERAP2, (8.67 fold change (FC)) HLA-DQB1 (7.88 FC) CD28 (2.60 FC), LILRA3 (2.87 FC) and TGFBR3 (2.1 FC)) Hierarchical clustering demonstrated a difference in global gene expression patterns between the samples from dystocic and non-dystocic labours. RT-PCR validation was performed on 4 genes ERAP2, CD28, LILRA3 and TGFBR3

Conclusion

These findings suggest an underlying molecular basis for dystocia in nulliparous women in spontaneous labor. Differentially expressed genes suggest an important role for the immune response in dystocic labor and may provide important indicators for new diagnostic assays and potential intrapartum therapeutic targets.

Genetic evidence of multiple loci in dystocia--difficult labour

BACKGROUND

Dystocia, difficult labour, is a common but also complex problem during childbirth. It can be attributed to either weak contractions of the uterus, a large infant, reduced capacity of the pelvis or combinations of these. Previous studies have indicated that there is a genetic component in the susceptibility of experiencing dystocia. The purpose of this study was to identify susceptibility genes in dystocia.

METHODS

A total of 104 women in 47 families were included where at least two sisters had undergone caesarean section at a gestational length of 286 days or more at their first delivery. Study of medical records and a telephone interview was performed to identify subjects with dystocia. Whole-genome scanning using Affymetrix genotyping-arrays and non-parametric linkage (NPL) analysis was made in 39 women exhibiting the phenotype of dystocia from 19 families. In 68 women re-sequencing was performed of candidate genes showing suggestive linkage: oxytocin (OXT) on chromosome 20 and oxytocin-receptor (OXTR) on chromosome 3.

RESULTS

We found a trend towards linkage with suggestive NPL-score (3.15) on chromosome 12p12. Suggestive linkage peaks were observed on chromosomes 3, 4, 6, 10, 20. Re-sequencing of OXT and OXTR did not reveal any causal variants.

CONCLUSIONS

Dystocia is likely to have a genetic component with variations in multiple genes affecting the patient outcome. We found 6 loci that could be re-evaluated in larger patient cohorts.

Genetic influence on dystocia

BACKGROUND

Dystocia-prolonged and difficult labor-is a common and worldwide problem during parturition. Epidemiological studies have suggested a familial aggregation. This study aimed to quantify the genetic influence (i.e. the heritability) on dystocia.

METHODS

A retrospective study of all births in Sweden from 1973 through 1997 was undertaken. Data from the population-based Swedish Birth, Twin and National Family Registers were linked on an individual basis. In total, 2,539,534 births were analyzed. Relationships between sibling and mother-daughter pairs were established. The relative risk for dystocia was calculated. Model-fitting (Mx) was used to estimate the relative contribution of genetic and environmental factors for liability to dystocia.

RESULTS

In all, 190,747 women were diagnosed with dystocia. Measures of familial similarity (relative risks and correlation of liability) for dystocia were higher in monozygotic than in dizygotic twins, other sibling pairs and mother-daughter pairs. Correlation of liability was also higher in full-sisters than in half-sisters. Model-fitting suggested that genetic effects accounted for 28%[95% confidence interval (CI) 21-32] of the susceptibility for dystocia.

CONCLUSION

Dystocia is a complex disorder of poor uterine action that is influenced by a significant genetic component as well as environmental factors. The amount of genetic influence makes it interesting to study the gene expression in these patients. Detection of the genes related to dystocia might lead to better pathophysiological understanding of this condition and the possibility of detecting these mothers before parturition.