Genetic influence on dystocia

Are There Similarities in Pregnancy Complications and Delivery Outcomes among Sisters?

This retrospective cohort study evaluated pregnancy outcomes and similarities between pairs of nulliparous sisters with a singleton fetus who delivered between 2013 and 2020. The “Sister-1 group” was defined as the sibling who delivered first, while the “Sister-2 group” included the siblings who gave birth after Sister-1. Obstetrical complications and delivery outcomes were compared. The relative risk for recurrence of a complication in Sister-2 was calculated. The study included 743 sister pairs. There were no between-group differences in maternal BMI, gestational age at delivery, gravidity, smoking, or epidural rates. The Sister-2 group was older than the Sister-1 group (26.4 ± 5 vs. 25.8 ± 4.7 years, respectively, p = 0.05). Higher birthweights and more large-for-gestational-age infants characterized the Sister-2 group compared with the Sister-1 group (3241 ± 485 g vs. 3148 ± 536 g, p < 0.001 and 7.7% vs. 4.8%, p = 0.025, respectively). There were no between-group differences in the rate of small-for-gestational-age, gestational diabetes, hypertensive disorders, pre-term births, vacuum extraction, or cesarean deliveries. Logistic regression analysis found that if Sister-1 underwent vacuum extraction, her sibling had an increased risk for vacuum delivery (adjusted RR 3.03, 95% CI 1.4−6.7; p = 0.003) compared with those whose sibling (Sister-1) did not. There was a three-fold risk of vacuum extraction delivery between sisters. This finding could be related to biological inheritance, environmental factors, and/or psychological issues that may affect similarities between siblings’ delivery outcomes.

The effect of ultrasonographically measured fetal adipose tissue components on labor

AIM

To investigate whether increased fetal adiposity diagnosed ultrasonographical is associated with labor dystocia, and increased risk of operative delivery.

METHOD

This was a prospective study and included 400 pregnant women between 37 and 41 weeks of gestation. In addition to standard ultrasonographic measurements, we evaluated fetal soft tissue thickness before delivery. We also recorded data on delivery method, shoulder dystocia, fetal birthweight and labor duration. We considered the period between 6 and 10 cm cervical opening as the active phase, and the period from full dilation to birth as the second stage.

RESULTS

While the vaginal delivery rate was 77.3%, a cesarean was performed in 22.7% of pregnant women. We found a positive correlation between fetal adipose tissue components and durations of the active phase and second-stage labor and the baby's birthweight. Also, we examined and determined that cesarean section and labor dystocia increased as the fetus adipose tissue thickness increased. We investigated the effect of parameters on the study results with logistic regression analysis and possible threshold values with receiver operating characteristics analysis.

CONCLUSION

Our study evaluated the fetal adipose tissue complex during delivery was significant in terms of labor dystocia and operative delivery. We think it may be a guide for future studies in the literature.

Defining arrest in the first and second stages of labor

Normal labor is identified as regular uterine contractions in addition to dilation and effacement of the cervix. It is necessary to define normal labor in order to delineate when a woman's labor pattern diverges from that observed in most women. Labor irregularities are subdivided into protraction disorders and arrest disorders. Identifying abnormal labor patterns and initiating appropriate interventions is essential because prolonged labor is associated with an increase in perinatal morbidity. The aim of this review was to delineate both normal labor progress and also discuss the current evidence-based diagnosis and treatment of protraction and arrest disorders. Many subtleties go into defining the boundaries of the first and second stages of labor. Historically, the Friedman curve established normal limits; but currently Zhang has advanced these definitions by accounting for current demographical characteristics and practice environments. The most significant variables for defining normal progress of labor are parity and regional anesthesia status. The most common causes of labor abnormalities are uterine inactivity, obesity, cephalopelvic disproportion and fetal malposition. Risks of extending the first and/or second stage of labor include postpartum hemorrhage, intraamniotic infection and potentially an increase in neonatal adverse outcomes. The management of labor disorders consists of oxytocin administration, amniotomy, intrauterine pressure catheter use and shared decision-making regarding proceeding with expectant management, operative vaginal delivery or cesarean delivery after weighing the risks and benefits of each option. The decision to extend the duration of labor is personalized for each mother-baby dyad and should be agreed upon depending on individual maternal and fetal circumstances.

Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma

Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.

Length of labour in mothers and their daughters: A matched cohort study

OBJECTIVE

Physiological length of labour is highly variable and population norms have low sensitivity and specificity for individuals. The birth history of mothers may provide a basis for personalized assessment of labour progress in their nulliparous daughters. This study was designed to investigate the relationship between length of labour in nulliparous daughters and in their mother's first birth, as a basis for constructing individualised labour prediction models in future.

STUDY DESIGN

A mother-daughter matched cohort study was conducted in two Israeli maternity hospitals. Recruitment took place between September 2014 and June 2015 via antenatal clinics. Inclusion criteria were nulliparous daughters with singleton pregnancies at ≥32 weeks' gestation and mothers of included daughters who had a first birth in hospital prior to 1997. Data were collected prospectively for daughters by questionnaire and from electronic hospital records, and through retrospective recall questionnaires for mothers. Mother-daughter length of labour data were analysed using parametric and non-parametric tests and logistic regression. Length of labour was categorized as ≤10 h and >10 h. Other factors influencing daughters' length of labour were also examined.

RESULTS

Data from 323 mother-daughter pairs were analysed. Univariate logistic regression analysis showed that daughters of mothers who were in active labour for more than 10 h showed increased likelihood of having a longer labour [OR1.91 (95 % CI 1.19, 3.05, P = 0.007)]. Controlling for infant gender increased the effect size [OR3.23 (95 % CI 1.55, 6.74, P = 0.002)]. Multivariable logistic regression indicated that mothers' length of labour [OR1.88 (95 % CI 1.12, 3.17)] and daughters' age [OR1.08 (95 % CI 1.02, 1.14)], weight gain in pregnancy [OR1.10 (95 % CI 1.04, 1.16)] and use of anesthesia, were statistically significant factors for daughters' length of labour, with sensitivity, specificity, and positive and negative predictive values of 74 %, 56 %, 66 %, and 64 %, respectively.

CONCLUSIONS

A strong positive association between mother and daughter lengths of labour was found. A model that includes length of labour in their mother's first birth might be useful for labour progress prediction for nulliparous women. Practitioners could inquire about maternal first birth patterns as an additional heuristic to guide practice and increase precision in the clinical management of nullipara women's labour and delivery.

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.

Cliff-edge model predicts intergenerational predisposition to dystocia and Caesarean delivery

The cliff-edge model explains the evolutionary persistence of relatively high incidences of fetopelvic disproportion (FPD), the mismatch of fetal and maternal dimensions during human childbirth. It also predicts that FPD rates have increased evolutionarily since the regular use of Caesarean sections. Here we show that the model also explains why women born by Caesarean because of FPD are about twice as likely to develop FPD in their own childbirth compared with women born vaginally. This theoretical prediction of a complex epidemiological pattern lends support to the cliff-edge model and its underlying assumptions.

Recently, we presented the cliff-edge model to explain the evolutionary persistence of relatively high incidences of fetopelvic disproportion (FPD) in human childbirth. According to this model, the regular application of Caesarean sections since the mid-20th century has triggered an evolutionary increase of fetal size relative to the dimensions of the maternal birth canal, which, in turn, has inflated incidences of FPD. While this prediction is difficult to test in epidemiological data on Caesarean sections, the model also implies that women born by Caesarean because of FPD are more likely to develop FPD in their own childbirth compared with women born vaginally. Multigenerational epidemiological studies indeed evidence such an intergenerational predisposition to surgical delivery. When confined to anatomical indications, these studies report risks for Caesarean up to twice as high for women born by Caesarean compared with women born vaginally. These findings provide independent support for our model, which we show here predicts that the risk of FPD for mothers born by Caesarean because of FPD is 2.8 times the risk for mothers born vaginally. The congruence between these data and our prediction lends support to the cliff-edge model of obstetric selection and its underlying assumptions, despite the genetic and anatomical idealizations involved.

Genetic Factors Are Not the Major Causes of Chronic Diseases

The risk of acquiring a chronic disease is influenced by a person’s genetics (G) and exposures received during life (the ‘exposome’, E) plus their interactions (G×E). Yet, investigators use genome-wide association studies (GWAS) to characterize G while relying on self-reported information to classify E. If E and G×E dominate disease risks, this imbalance obscures important causal factors. To estimate proportions of disease risk attributable to G (plus shared exposures), published data from Western European monozygotic (MZ) twins were used to estimate population attributable fractions (PAFs) for 28 chronic diseases. Genetic PAFs ranged from 3.4% for leukemia to 48.6% for asthma with a median value of 18.5%. Cancers had the lowest PAFs (median = 8.26%) while neurological (median = 26.1%) and lung (median = 33.6%) diseases had the highest PAFs. These PAFs were then linked with Western European mortality statistics to estimate deaths attributable to G for heart disease and nine cancer types. Of 1.53 million Western European deaths in 2000, 0.25 million (16.4%) could be attributed to genetics plus shared exposures. Given the modest influences of G-related factors on the risks of chronic diseases in MZ twins, the disparity in coverage of G and E in etiological research is problematic. To discover causes of disease, GWAS should be complemented with exposome-wide association studies (EWAS) that profile chemicals in biospecimens from incident disease cases and matched controls.

The predictive capacity of personal genome sequencing

New DNA sequencing methods will soon make it possible to identify all germline variants in any individual at a reasonable cost. However, the ability of whole-genome sequencing to predict predisposition to common diseases in the general population is unknown. To estimate this predictive capacity, we use the concept of a "genometype." A specific genometype represents the genomes in the population conferring a specific level of genetic risk for a specified disease. Using this concept, we estimated the maximum capacity of whole-genome sequencing to identify individuals at clinically significant risk for 24 different diseases. Our estimates were derived from the analysis of large numbers of monozygotic twin pairs; twins of a pair share the same genometype and therefore identical genetic risk factors. Our analyses indicate that (i) for 23 of the 24 diseases, most of the individuals will receive negative test results; (ii) these negative test results will, in general, not be very informative, because the risk of developing 19 of the 24 diseases in those who test negative will still be, at minimum, 50 to 80% of that in the general population; and (iii) on the positive side, in the best-case scenario, more than 90% of tested individuals might be alerted to a clinically significant predisposition to at least one disease. These results have important implications for the valuation of genetic testing by industry, health insurance companies, public policy-makers, and consumers.

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.

Is difficult childbirth related to postpartum maternal outcomes in the early postpartum period?

Unplanned, adverse events during labor or delivery may generate a negative response during the early postpartum period, resulting in disruption of usual functioning and mood. High levels of maternal depressive symptoms are associated with parenting, infant attachment, behavioral problems and cognition (Beck 2002). The purpose of this study was to examine the relationship of adverse events in labor or delivery and depressive symptoms, functional status and infant care at 2-weeks postpartum. The secondary aim was to explore the role of social support as a possible moderator in the relationship between adverse birth events and maternal outcomes. A secondary analysis of data (n = 123) was performed using data collected in a prospective, observational study examining the effects of antidepressant use during pregnancy. Adverse events did not significantly predict depressive symptoms (odds ratio = 1.34, p = .536), functional status (R(2) change = .001, p = .66), or infant care (R(2) change = .004, p = .48) at 2-weeks postpartum when controlling for depression during pregnancy, antidepressant use at delivery, education level, age, and parity. Social support had significant effects on depressive symptoms (p = .02), functional status (p = .014), and infant care (p < .001) but did not moderate the effect of adverse events when predicting depressive symptoms (odds ratio = 1.01, p = .045), functional status (R(2) change = .009, p = .056) and infant care (R(2) change < .001, p = .92). Adverse events did not predict maternal outcomes at 2-weeks postpartum. Social support was related to depressive symptoms, functional status and infant care, but did not moderate the effects of adverse events.