Genetic evidence of multiple loci in dystocia--difficult labour

Oxytocin receptor gene (OXTR) and father support interact to predict depressive symptoms postpartum

Postpartum depression (PPD) is a debilitating mental illness affecting approximately 13% of mothers after birth. Both genetic and psychosocial factors contribute to PPD risk, but very little is known about how these factors interact. We tested whether the rs53576 polymorphism in the oxytocin receptor (OXTR) gene accounts for variation in the impact of low social support as a risk factor for depression among mothers during the perinatal period. New mothers (N = 220) provided saliva or blood DNA samples and completed surveys assessing PPD symptoms and perceived social support. In a significant interaction, social support from the baby's father predicted PPD symptoms to a greater extent among mothers with the GG compared to AG and AA genotypes. These results add to converging evidence that variation in OXTR rs53576 moderates the impact of the social environment on PPD.

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.

Pharmacogenetics in obstetric anesthesia

The 21st century has been billed as the era of "precision/personalized medicine." Genetic investigation of clinical syndromes may guide therapy as well as reveal previously unknown biological or pharmacological pathways that may result in novel drug therapies. Several clinical issues in obstetrics and obstetric anesthesiology have been targets for genetic investigations. These include evaluation of the genetic effects on preterm labor and the progression of labor, spinal anesthesia-induced hypotension and the response to medications used to treat hypotension, and the effect of gene variants on pain and analgesic responses. Most studies have examined specific single nucleotide polymorphisms. Findings have revealed modest effects of genetic variation without tangible impact on current clinical practice. Over the next decade, increased availability of whole exome and genome sequencing, epigenetics, large genetic databases, computational biology and other information technology, and more rapid methods of real-time genotyping may increase the impact of genetics in the clinical arena of obstetrics and obstetric anesthesia.

Transverse lie with prolapsed arm in a female red-howler monkey (Alouatta guariba clamitans - Cabrera, 1940)

This study focuses on a case of a red-howler monkey (Alouatta guariba clamitans) which was found with a fetus in a transverse lie position with a prolapsed arm. The topic of this research is well justified as there are no data on this condition involving this type of non-human primate in literature. In this study, a red-howler monkey was observed by locals pulling at her pelvic region for 3 days near a farm. On the third day, the monkey was found lying on the ground at which point she offered no resistance when approached. The environmental police took the monkey to receive medical attention. During the physical examination, it was quickly observed that the monkey was pregnant; the right forelimb of the fetus was exposed from the vulva. An ultrasound revealed a non-viable fetus, and due to the severe weakness of the mother, we opted for euthanasia. During the necropsy, not only was the fetus found macerated but it was also in a transverse lie position with a prolapsed arm and presented no external or internal injuries consistent with trauma.

Insights from physiology into myometrial function and dysfunction

NEW FINDINGS

What is the topic of this review? I focus on clinical aspects of uterine physiology, specifically, myometrial contractility. I bring together and contrast findings using physiological approaches and those using newer techniques, 'omics'. What advances does it highlight? Physiological studies have recently shed light on the myometrium in twin pregnancies, but there have been no 'omic' approaches. In contrast, studies of preterm delivery using newer approaches are generating new research avenues, whereas traditional approaches have not flourished. Finally, I describe significant advances in understanding of 'slow-to-progress' labours, achieved using physiological and clinical approaches. Advances in molecular, genetic and 'omic' technologies are fuelling the thirst for better understanding of the uterus and application of this information to problems in pregnancy and labour. Progress has, however, been limited while we still have an incomplete understanding of some of the basic physiology of uterine smooth muscle (myometrium). In this review and opinion piece, I explore some of the fascinating findings from selected recent studies and see how these may provide new avenues for physiological and clinical research. It is also the case, however, that there is still limited mechanistic understanding about physiological and pathophysiological processes in the myometrium. This lack of understanding limits the usefulness of some findings from genomic and allied studies. By focusing on some key recent findings and relating these to two important clinical problems in childbirth that involve myometrial activity, namely preterm delivery and difficult labours, the interplay between our physiological knowledge and the information provided by newer technologies is explored. My opinion is that physiology has provided much more new mechanistic insight into difficult births and that the newer technologies may lead to breakthroughs in preterm birth research, but that this has not yet happened.

Factors associated with higher oxytocin requirements in labor

OBJECTIVE

To identify clinical characteristics associated with high maximum oxytocin doses in women who achieve complete cervical dilation.

METHODS

A retrospective nested case-control study was performed within a cohort of all term women at a single center between 2004 and 2008 who reached the second stage of labor. Cases were defined as women who had a maximum oxytocin dose during labor >20 mu/min, while women in the control group had a maximum oxytocin dose during labor of ≤20 mu/min. Exclusion criteria included no oxytocin administration during labor, multiple gestations, major fetal anomalies, nonvertex presentation, and prior cesarean delivery. Multiple maternal, fetal, and labor factors were evaluated with univariable analysis and multivariable logistic regression.

RESULTS

Maximum oxytocin doses >20 mu/min were administered to 108 women (3.6%), while 2864 women received doses ≤20 mu/min. Factors associated with higher maximum oxytocin dose after adjusting for relevant confounders included maternal diabetes, birthweight >4000 g, intrapartum fever, administration of magnesium, and induction of labor.

CONCLUSIONS

Few women who achieve complete cervical dilation require high doses of oxytocin. We identified maternal, fetal and labor factors that characterize this group of parturients.

Genetic contributions to labor pain and progress

Studies on genetic contributions to labor analgesia have essentially evaluated the μ-opioid receptor gene (OPRM1), with some evidence that p.118A/G of OPRM1 influences the response to neuraxial opioids. As for labor progress, the β2-adrenergic receptor gene (ADRB2) is associated with preterm labor and delivery, and impacts the course of labor. Taken together though, there is no evidence that pharmacogenetic testing is needed or beneficial in the context of obstetric anesthesia; however, realizing the influence of genetic variants on specific phenotypes provides the rationale for a more cautious interpretation of clinical studies that attempt to find a dose-regimen that fits all.

Associations between the oxytocin receptor gene (OXTR) and "mind-reading" in humans--an exploratory study

BACKGROUND/AIMS

The application of intranasal oxytocin enhances facial emotion recognition in normal subjects and in subjects with autism spectrum disorders (ASD). In addition, various features of social cognition have been associated with variants of the oxytocin receptor gene (OXTR). Therefore, we tested for associations between mind-reading, a measure for social recognition and OXTR polymorphisms.

METHODS

76 healthy adolescents and young adults were tested for associations between OXTR rs53576, rs2254298, rs2228485 and mind-reading using the "Reading the Mind in the Eyes Test" (RMET).

RESULTS

After Bonferroni correction for multiple comparisons, rs2228485 was associated with the number of incorrect answers when subjects evaluated male faces (P =0.000639). There were also associations between OXTR rs53576, rs2254298 and rs2228485 and other RMET dimensions according to P <0.05 (uncorrected).

CONCLUSION

This study adds further evidence to the hypothesis that genetic variations in the OXTR modulate mind-reading and social behaviour.

The obstetric dilemma: an ancient game of Russian roulette, or a variable dilemma sensitive to ecology?

The difficult birth process of humans, often described as the "obstetric dilemma," is commonly assumed to reflect antagonistic selective pressures favoring neonatal encephalization and maternal bipedal locomotion. However, cephalo-pelvic disproportion is not exclusive to humans, and is present in some primate species of smaller body size. The fossil record indicates mosaic evolution of the obstetric dilemma, involving a number of different evolutionary processes, and it appears to have shifted in magnitude between Australopithecus, Pleistocene Homo, and recent human populations. Most attention to date has focused on its generic nature, rather than on its variability between populations. We re-evaluate the nature of the human obstetric dilemma using updated hominin and primate literature, and then consider the contribution of phenotypic plasticity to variability in its magnitude. Both maternal pelvic dimensions and fetal growth patterns are sensitive to ecological factors such as diet and the thermal environment. Neonatal head girth has low plasticity, whereas neonatal mass and maternal stature have higher plasticity. Secular trends in body size may therefore exacerbate or decrease the obstetric dilemma. The emergence of agriculture may have exacerbated the dilemma, by decreasing maternal stature and increasing neonatal growth and adiposity due to dietary shifts. Paleodemographic comparisons between foragers and agriculturalists suggest that foragers have considerably lower rates of perinatal mortality. In contemporary populations, maternal stature remains strongly associated with perinatal mortality in many populations. Long-term improvements in nutrition across future generations may relieve the dilemma, but in the meantime, variability in its magnitude is likely to persist.

Oxytocin and catechol-O-methyltransferase receptor genotype predict the length of the first stage of labor

OBJECTIVE

We aimed to identify genetic factors that influence the rate of the first stage of labor.

STUDY DESIGN

We prospectively enrolled 233 laboring nulliparous parturients. Demographic, clinical, and genetic data were collected. We evaluated the influence of population and individual variability using a nonlinear mixed effects model.

RESULTS

Parturients who were homozygous for "G" at oxytocin receptor gene rs53576 transitioned to active labor later and thus had slower labor. Catechol-O-methyltransferase rs4633 genotype TT was associated with slower latent phase labor. Labor induction with prostaglandin was associated with faster labor, and request for meperidine was associated with slower labor. Birthweight was related inversely to the rate of the active phase.

CONCLUSION

There are demographic, clinical, and genetic factors that influence an individual's rate of labor progress. This information could be used in automated form to improve the prediction of the length of the first stage of labor.

Oxytocin in the treatment of dystocia in mice

Physicians and veterinarians often prescribe oxytocin to treat dystocia. However, oxytocin administration to pregnant women or animals is not without risk. In the venue of laboratory animal medicine, the use of oxytocin may present confounding variables to research. Although oxytocin has been studied extensively, many of its physiologic effects and interactions with other hormones remain unclear. Investigator concerns about adverse and confounding effects of oxytocin in their research mice prompted the current review of oxytocin and its use to treat murine dystocia. Well-controlled studies of oxytocin in dystocic mice have not been conducted. However, in humans and other animals, inconsistent and adverse effects are well-documented. Limited knowledge of the complex physiologic and molecular mechanisms of action of oxytocin and scant support for the efficacy of oxytocin in dystocic mice fail to meet the standards of evidence-based veterinary medical practice. The administration of oxytocin is contraindicated in many cases of dystocia in research mice, and its use in dystocic mice may be unfounded. A brief review of oxytocin and the physiologic mechanisms of parturition are provided to support this conclusion. Alternative treatments for murine dystocia are discussed, and a holistic approach is advocated to better serve animal welfare and to safeguard the integrity of valuable research. Laboratory animal veterinarians overseeing the development of guidelines or standard operating procedures for technician or investigator treatment of dystocic mice should understand the effects of oxytocin administration in light of relevant research.