Sex Twins Research Articles

Epigastric heteropagus twinning with dextrocardia: a case report

Abstract Background Heteropagus twinning is a rare birth defect in 1 in million live births. Epigastric heteropagus is the most frequent type, in which a smaller dependent (parasite twin) is attached to the body of the host (autosite twin) to the thorax and umbilicus. Several congenital anomalies have been previously described in the host twin. We describe the first case of epigastric heteropagus twinning with dextrocardia and situs inversus in which a successful surgical separation is performed. Case presentation A 48-h-old female sex twins were presented to Bahawal Victoria Hospital. A careful anatomic study using contrast X-ray, magnetic resonance imaging, and echocardiogram showed epigastric heteropagus twinning and situs inversus in autosite twin. A successful surgical separation was performed, and the parasite twin was removed from the body of the autosite twin. Conclusions Antepartum screening detects congenital malformations; however, several pregnancies are unsupervised in underdeveloped countries. In the case of heteropagus twinning, careful surgical separation in the absence of complications leads to the favorable survival of the autosite twin.

Degree of leukochimerism with calf age in Angus-crossbred twin sets.

Twinning in cattle is infrequent and usually undesired. It can result in an increased occurrence of abortion and dystocia, reduced calf survival and a high likelihood of freemartinism in mixed-sex twins. Twin gestations are also commonly associated with the formation of placental vascular anastomoses (PVA) between twins. Through PVA they share blood, hormones (leading to freemartinism in mixed sex twins) and hematopoietic stem cells, which are the progenitors of white blood cells. The sharing of stem cells between twins can result in leukochimeric twin sets. These are twins that have white blood cells derived from both self and the co-twin owing to the fetal migration of hematopoietic stem cells from the extraembryonic mesoderm of the yolk sac to final sites like bone marrow and thymus. This study examined the degree to which this leukochimerism changes with age. DNA was extracted from hair bulbs containing mesenchymal dermal papilla to determine the individual's true genotype and blood samples were obtained at six time points from 1 week to 8 months of age to assess leukochimerism. Samples were genotyped using a medium density SNP chip, and quantitative estimates of allele frequency were determined using SNPs for which members of a twin set had alternative homozygous genotypes. The results indicate statistically significant changes in the proportion of self and co-twin with age and suggest that by 2-4 months of age the genotypic mix in white blood cells represents the hematopoetic stem cell population resident in the individual (i.e. permanently found in thymus and bone marrow).

Parental resources and heritability as factors shaping children's health. An analysis of twins' self-rated health using TwinLife.

We assess the relative and joint contributions of genetic and environmental factors on health during childhood and assume that parental resources are part of the environmental factors shaping children's health. We discuss theoretical background and empirical evidence concerning the effects of parental resources and heritability on children's health. Based on these findings we formulate six hypotheses guiding our empirical analysis, using data from TwinLife, a nationally representative sample of same sex twin pairs in Germany. We analyze self-rated health of 1,584 twin pairs aged 4-18. We did find strong support for the idea that parental resources influence children's health: household income and fathers' education consistently show positive effects. In contrast to our expectation, we did not find that genetic factors influence the health of well-off children less than the health of children living in families with lower SES. We also did not find that the genetic influence on health increases during childhood and adolescence. On the contrary our results indicate that the role played by genetic factors diminishes whereas environmental factors gain importance for health of children while growing up. This finding is good news for those interested in improving health chances of children from lower SES backgrounds because it demonstrates the malleability of children's health.

Epidemiology of bovine colostrum production in New York Holstein herds: Cow, management, and environmental factors

Adequate supply of high-quality colostrum is essential for calf health. Colostrum production, at first milking, varies between animals and seasons, but herd-level and management associations with colostrum production have not been well described. Our objectives were to (1) describe colostrum production and colostrum handling practices and (2) to identify individual cow, herd management, and environmental factors associated with colostrum production. A convenience sample of 19 New York Holstein dairy farms (620 to 4,600 cows) were enrolled in this observational study to describe colostrum production and to evaluate cow, management, and prepartum environmental factors associated with colostrum yield and Brix %. Herd owners or managers were given a colostrum management questionnaire, and farm personnel recorded individual colostrum yield and Brix % for primiparous (PP; n = 5,978) and multiparous (MPS; n = 13,228) cows between October 2019 and February 2021. Temperature, relative humidity, and light intensity were measured by sensors placed in each farm's close-up dry cow pens for the entire length of the study. Median colostrum yield for each farm ranged from 2.5 to 7.6 kg for PP and 4.0 to 7.7 kg for MPS cows. Mean Brix % from each farm ranged from 22.2 to 27.9% for PP and 22.0 to 28.8% for MPS cows. Lowest colostrum yield from PP animals was associated with calf sex (female) and colostrum Brix % (≤22%). Greatest colostrum yield from MPS cows was associated with colostrum Brix % (≤22%), calf sex (twin), dry period length (>67 d), gestation length (283-293 d), an alive calf, second parity, previous lactation length (>344 d) and previous lactation 305-d mature equivalent milk yield (>13,091 kg), heat and humidity exposure area under the curve (AUC) 7 d before calving (>69.2 average temperature-humidity index per 30-min interval), and light intensity AUC 14 d before calving (>154.2 average lux per 15-min interval). Greatest colostrum Brix % from PP animals was associated with calf sex (male), an alive calf, and light intensity AUC 14 d before calving (≤64.0 average lux per 15-min interval). Greatest colostrum Brix % from MPS cows was associated with dry period length (>67 d), an alive calf, 305-d mature equivalent milk yield of previous lactation (≤15,862 kg), gestation length (274-282 d), colostrum yield (<6 kg), fifth or greater parity, and heat and humidity exposure AUC 7 d before calving (≤50.1 average temperature-humidity index per 30-min interval). Dairy producers can use this information to recognize the variation in colostrum production and alter colostrum management programs in anticipation of periods of low production or quality.

Educational gender gap in sub-Saharan Africa: Does the estimation method matter? A comparison using a sample of opposite sex twins

A robust assessment of the gender educational gap addressing all channels behind gender discrimination is necessary. Using data for over 30 sub-Saharan Africa (SSA) countries and household and twin fixed-effects approaches, I estimate this inequality across the lifecourse, controlling for variables that are the same within households or twins, yielding a better understanding of the association of gender with education outcomes. Estimates show that gender inequality is still a significant barrier in SSA, but its extent is somewhat over-estimated by monitoring platforms of SGD4. The analysis indicates that more emphasis should be placed on investigating unobserved factors behind gender discrimination.

Genetic and environmental correlations between the General Factor of Personality (GFP) and working memory

The present study examines the association between the General Factor of Personality (GFP) and working memory and its etiology with a behavioral genetic approach. The GFP, which explains the common variance among lower-order personality traits, is considered to reflect social effectiveness. Meanwhile, working memory also plays a significant role in social competence. Hence, we expected a substantial association between the GFP and working memory. A total of 253 Japanese twin pairs (124 monozygotic female; 52 monozygotic male; 28 dizygotic female; 17 dizygotic male; and 32 opposite sex twins) were included in the analyses. Phenotypic analyses confirmed a significant positive correlation between the GFP and working memory. Biometric analysis with a bivariate Cholesky decomposition model showed that the phenotypic correlation derived from additive genetic and non-shared environmental correlations. The present findings are in line with social effectiveness account of the GFP.

Cord blood androgen levels of females from same sex and opposite sex twins - A pilot study.

Opposite-sex twins have shown behavioural and reproductive differences between females and males. These differences may be determined by higher intrauterine levels of androgens among females that were exposed to a male co-twin. The aim of this study was to compare cord blood androgen levels in females from same-sex and opposite-sex twins. A prospective study. In this pilot study, we compared cord blood androgens (DHEA-S, Δ-4 androstenedione, total testosterone-TT) and sex hormone-binding globulin (SHBG) levels in 20 females from same sex and 20 females from opposite-sex dichorionic diamniotic twins. We used generalized estimating equation (GEE) modelling to assess differences in cord blood androgens between females from same-sex twin pregnancies and females from opposite-sex twin pregnancies. Twenty opposite-sex twin pairs (female-male twins) and 20 same-sex twin pairs (female-female). Cord blood total testosterone, Δ-4 androstenedione, DHEA-S and sex hormone-binding globulin (SHBG) levels. No difference in the levels of androgens as Δ-4 androstenedione, total testosterone and SHBG was identified between females that were exposed to a female co-twin compared with females that were exposed to a male co-twin. DHEA-S levels were significantly lower among females from opposite-sex twins compared with females from same-sex twins. Our preliminary data do not support the hypothesis that femalesexposed to male co-twins are exposed to higher levels of androgens in utero compared with females exposed to female co-twins. Further studies are needed to explain the reported behavioural and reproductive differences among opposite-sex twins.

Transvaginal nUltrasound Measurement of Lower Uterine Segment Myometrial Thickness for the Prediction of Preterm Labor in Twins Gestations. Observational Study

Background: Transvaginal ultrasound evaluation of cervical length considered a good predictor of PTL and recently lower uterine segment myometrial thickness had been used for this purpose. Objectives: Evaluating the efficacy and validity of transvaginal ultrasound measurement of lower uterine segment myometrial thickness (LUS-MT) in prediction of preterm delivery (PTL) in twins pregnancies. Patients and Methods: This is an observational prospective cohort study where ninety sex (96) twins pregnant women were enrolled. LUS-MT and CL were measured by transvaginal ultrasound between 16-24 gestational weeks. All patients were scheduled for routine antenatal care till delivery and divided in two groups: preterm group and full-term group. Results: 58 patients delivered at full term and 38 patients had preterm delivery. Among patients who had preterm delivery, 25 patients (56.8%) had LUS-MT <4.26 and 2 patients (3.8%) only had LUS-MT ≥4. among patients who delivered at full term, 50 patients (96.2%) had LUS-MT ≥4.26 and 19 patients (43.2%) had LUS-MT <4.26. The best cutoff value for LUS was 4.26 mm with area under the ROC curve (AUC) 0.917, sensitivity 92.1 %, specificity 86.2%, PPV 81.3%, NPV 94.3% and Accuracy 92.1 %. Conclusion: Transvaginal ultrasound measurement of LUS-MT is an effective, precise, applicable and safe procedure in predicting the preterm labor in twins gestation with high validity than cervical length. Use of lower uterine wall as a substitution of CL measurement in order to predict population at risk of preterm labor needs to be investigated.

Transvaginal nUltrasound Measurement of Lower Uterine Segment Myometrial Thickness for the Prediction of Preterm Labor in Twins Gestations. Observational Study

Background: Transvaginal ultrasound evaluation of cervical length considered a good predictor of PTL and recently lower uterine segment myometrial thickness had been used for this purpose. Objectives: Evaluating the efficacy and validity of transvaginal ultrasound measurement of lower uterine segment myometrial thickness (LUS-MT) in prediction of preterm delivery (PTL) in twins pregnancies. Patients and Methods: This is an observational prospective cohort study where ninety sex (96) twins pregnant women were enrolled. LUS-MT and CL were measured by transvaginal ultrasound between 16-24 gestational weeks. All patients were scheduled for routine antenatal care till delivery and divided in two groups: preterm group and full-term group. Results: 58 patients delivered at full term and 38 patients had preterm delivery. Among patients who had preterm delivery, 25 patients (56.8%) had LUS-MT <4.26 and 2 patients (3.8%) only had LUS-MT ≥4. among patients who delivered at full term, 50 patients (96.2%) had LUS-MT ≥4.26 and 19 patients (43.2%) had LUS-MT <4.26. The best cutoff value for LUS was 4.26 mm with area under the ROC curve (AUC) 0.917, sensitivity 92.1 %, specificity 86.2%, PPV 81.3%, NPV 94.3% and Accuracy 92.1 %. Conclusion: Transvaginal ultrasound measurement of LUS-MT is an effective, precise, applicable and safe procedure in predicting the preterm labor in twins gestation with high validity than cervical length. Use of lower uterine wall as a substitution of CL measurement in order to predict population at risk of preterm labor needs to be investigated.

Prenatal Sonographic Detection of Monochorionic Twins with Bipartite Placenta

Background Determination of placentation and amnionicity is important for antenatal and intrapartum management in twin gestations. We present an typical monozygotic twin placenta and underscore the sonographic features and diagnostic pitfalls that may interfere with antenatal diagnosis. Case report: A 35-year-old G4P2 with a spontaneous pregnancy applied for routine second trimester anomaly screening. Upon prenatal ultrasonography at 20 weeks, an anatomically normal, same sex twin pregnancy was detected. A thin dividing membrane and a T-sign suggestive of a monochorionic diamniotic pregnancy were visualized. Antenatal follow-up was uneventful. Cesarean delivery was performed at 37 week. Postpartum examination revealed two distinct placental discs connected with each other through membranes. Microscopic examination of the membranes supported monochorionicity. Short Tandem Repeat Profile Analysis revealed identical pattern and confirmed monozygosity. Conclusion: Two separate placentas with a T-sign in same-sex twins should raise the suspicion of monozygosity, and should be followed accordingly.

Similarity in Teacher Ratings of the Externalizing Behavior of Twins: A Meta-Analysis

Valid and reliable teacher ratings serve as the foundation for screening and assessment of youth with behavioral disorders and twin studies offer an opportunity to study those ratings. We conducted a meta-analysis of 15 empirical investigations of aggressive and rule-breaking behavior using teacher ratings in the context of a twin research design. We retrieved n = 53 correlations from n = 7,885 pairs of monozygotic (MZ) twins and n = 67 correlations from n = 11,696 pairs of dizygotic (DZ) twins with two goals: (a) to test the best-fitting models for predicting similarity (correlations) in teacher ratings of MZ and DZ twin pairs and (b) to identify significant predictors in the respective models. We found that, for both MZ and DZ twins, the best-fitting model included all predictors and interactions. In the MZ model, we found a significant positive interaction between the percentage of same teachers who completed the ratings and male twins; in the DZ model, we found a significant negative interaction between the percentage of same teachers who completed the ratings and opposite sex twins. Teacher ratings converged and diverged in expected ways, advancing research in the context of the attributions-bias-context (ABC) model of informant ratings.

A population-based heritability estimate of bipolar disorder – In a Swedish twin sample

Twin- and family studies have shown variations in the heritability estimates of bipolar disorder (BPD). The current study uses an updated statistical methodology for heritability estimation in BPD by taking available time of follow-up into account while controlling for co-variates. We identified monozygotic and dizygotic same and different sex twins with BPD (n = 804) or unaffected from BPD (n = 91,604) from the Swedish Twin Register and the National Patient Register. We applied structural equational modeling with inversed probability weighting to estimate the heritability, taking into account censoring and truncation of data. Sex-limitation models were constructed to analyze qualitative or quantitative sex-differences in BPD. Heritability for BPD was 60.4% (95% Confidence Interval: 50.3–70.5) after age, sex, left-hand truncation and censoring of the data was taken into account. A larger proportion of females were affected from BPD (females 62.2%; males 37.8%, p < 0.001), but no sex-difference in BPD heritability was found, nor any sex-specific genetic effects. We demonstrated a robust 60% heritability for BPD with no evidence of sex-specific genetic effects on disease liability.

Childhood language development and later alcohol use behaviors

BackgroundStudies have shown a correlation between language abilities and alcohol use; however, results are inconsistent. A recent study using a discordant twin design showed an association between early child language development and later alcohol use behaviors; i.e., the twin with more advanced language abilities was more likely to try alcohol earlier in adolescence (Latvala et al., 2014). The authors suggested that this could result from better socialization of individuals with greater language abilities, which could lead to more opportunities for alcohol experimentation. The findings by Latvala et al. raise interesting questions, but the study has limitations, and replication is needed. MethodWe aimed to replicate and build upon these results utilizing 488 same sex twin pairs from the Colorado Longitudinal Twin Study, a longitudinal sample with quantitative measures of language abilities starting when the twins were 14 months old. ResultsWe found no significant correlations between a latent measure of child language abilities or measures of general cognitive ability at ages 14, 20, and 24 months and a latent alcohol use variable at ages 17 and 22 years. ConclusionOur results did not replicate the association between early language ability and later alcohol use reported by Latvala et al. Possible reasons for differing results across samples, including varying cultural norms as well as differences in educational attainment, peer influences, and novelty seeking, were discussed.

Relations of laterality and chewing sidedness in twins.

To study, whether there are associations between chewing side preference and other lateralities, whether there is a genetic origin for preferred chewing side (PCS), relations to sex, birth order and orthodontic treatment. The study included 113 twin pairs, 57 pairs monozygotic, 47 pairs same sex dizygotic and 9 pairs of opposite sex. The lateralities of preferred chewing side, footedness and eyedness were assessed by functional tests and handedness was checked by asking. Right-handed, -footed and -eyed as separated groups, and true-right sided (combined), were evenly distributed by preferred chewing side. By contrast, left-handed, -footed, -eyed and non-right sided used more left or both sides when chewing. Birth order affected preferred chewing side among monozygotic: the first-born twin was more likely to have the preferred chewing side on the non-right, whereas second-born twins used right side. Gender, zygosity and orthodontic treatment were not statistically significant factors. Examination of chewing sidedness could have been done in several different ways to provide a definite result. Sample size of opposite sex twins was very small. Preferred chewing side generally seemed to follow the side where other lateralities occur; however, monozygotic twins seemed to be more receptive to it. True-right sided were more evenly distributed than non-right sided by the preferred chewing side.

Impact of genetics on third molar agenesis

The purpose of this investigation was to determine the impact of heritability on third molar agenesis in twins. The study sample consisted of 284 same sex twins (172 monozygotic and 112 dizygotic), whose mean ages were 19.7 ± 4.3 and 18.9 ± 4.8 years, respectively. The monozygotic group consisted of 36.3% males and 63.7% females, while the dizygotic group consisted of 50.1% males and 49.9% females. The zygosity of the twins was established using 15 specific DNA markers. The prevalence of third molar agenesis in monozygotic twins was 19.6%, which was higher than in the dizygotic twins group (15.50%) (p = 0.004). In both groups, third molar agenesis was more frequent in the maxilla than in the mandible (p = 0.000). Agenesis of the maxillary third molars was mostly affected by additive genetic factors (62–63%), with the common environment and the specific environment accounting for up to 25% and 13%, respectively. In contrast, agenesis of the lower third molars was associated with a higher additive genetic determination (81–83%), with the specific environment accounting for 17% to 19%. The study’s conclusion is that the formation of the third molars follicle is strongly controlled by additive genetic factors.

Majority of human traits do not show evidence for sex-specific genetic and environmental effects

Sex differences in the etiology of human trait variation are a major topic of interest in the social and medical sciences given its far-reaching implications. For example, in genetic research, the presence of sex-specific effects would require sex-stratified analysis, and in clinical practice sex-specific treatments would be warranted. Here, we present a study of 2,335,920 twin pairs, in which we tested sex differences in genetic and environmental contributions to variation in 2,608 reported human traits, clustered in 50 trait categories. Monozygotic and dizygotic male and female twin correlations were used to test whether the amount of genetic and environmental influences was equal between the sexes. By comparing dizygotic opposite sex twin correlations with dizygotic same sex twin correlations we could also test whether sex-specific genetic or environmental factors were involved. We observed for only 3% of all trait categories sex differences in the amount of etiological influences. Sex-specific genetic factors were observed for 25% of trait categories, often involving obviously sex-dependent trait categories such as puberty-related disorders. Our findings show that for most traits the number of sex-specific genetic variants will be small. For those traits where we do report sexual dimorphism, sex-specific approaches may aid in future gene-finding efforts.

A case report of opposite sex twin pairs in which one had female to male gender dysphoria

The etiology of gender dysphoria (GD) is not fully known. In recent years, there are studies suggesting that the development of GD is related to some biological mechanisms. The hypothesis conveying that there is a biological background in the development of GD emphasize the importance of exposure to sex hormones in prenatal period. According to this hypothesis, while prenatal exposure to sex hormones causes development of male identity, non-exposure results with female identity. This hypothesis is supported with determination of the relationship between prenatal exposure to testosterone and masculine behaviors, in complete androgen insensitivity syndrome mostly development of female identity, and presence of near values of 2nd and 4th finger ratio in individuals with GD and the individuals with the sex they want to pass. In this article, one of the twins is male and the other one is female-to-male GD case was discussed in terms of the roles of prenatal exposure to sex hormones in the etiology of GD.

Variability of Cerebral Deep Venous System in Preterm and Term Neonates Evaluated on MR SWI Venography.

The anatomy of the deep venous system is characterized by a great variability that might play an important role in the pathogenesis of brain lesions in the preterm brain. The aim of this study was to compare the anatomy of cerebral subependymal veins evaluated on SWI venography in 3 groups of neonates with normal brain MR imaging (very preterm [gestational age <32 weeks], moderate-to-late preterm [gestational age ≥32 to ≤37 weeks], and term neonates [gestational age >37 weeks]) and to evaluate the influence of preterm birth on development of subependymal veins. SWI venographies of 84 very preterm, 31 moderate-to-late preterm, and 50 term neonates were retrospectively evaluated. Subependymal vein anatomy was classified into 6 different patterns: type 1 represented the classic pattern and types 2-6 were considered anatomic variants. A χ2 test was used to evaluate differences between the distributions of subependymal vein patterns. A significant difference (P = .011) was noticed between the 6 patterns based on gestational age. Type 1 was more frequent in term neonates (68%) than in both very preterm (41.7%) and moderate-to-late preterm neonates (56.5%). Anatomic variants were more common in very preterm neonates (66%) than in both moderate-to-late preterm (41%) and term neonates (36%). Interhemispheric asymmetry was more frequent in very preterm (59.5%) and moderate-to-late preterm neonates (51.6%) than in term neonates (34%; P = .017). Sex and monozygotic twin birth did not significantly affect the frequency of subependymal vein patterns (P = .0962). The deep venous system of the neonatal brain shows a large spectrum of anatomic variants with higher variability of subependymal vein anatomy in preterm than term neonates, likely related to the influence of the preterm birth and epigenetic factors on subependymal vein development.

Musculoskeletal pain and work absence – a 10 year follow-up study of Norwegian young adult twins

Background and aims: Sickness absence (SA) and disability pension (DP) are increasingly recognized asmajor public problems. Musculoskeletal disorders are among the most common diagnoses set by physiciansgranting SA and DP. Results from recent twin studies have established that SA and DP are influencednot only by environmental and social factors, but also moderately to substantially by genes. The aim of thecurrent study was to examine to what degree musculoskeletal complaints in young adults predict SA andDP, including SA granted for other diagnoses. As the participants were twins, we were able to performwithin pair analyses, to see if the associations between musculoskeletal pain and later DP or SA were confoundedby unmeasured genetic and shared environmental factors.Materials and methods: The Norwegian twin registry includes a questionnaire conducted in 1998. Fromthis, we included three measures of recurrent pain (lower back, neck/shoulders and muscular) as well assymptoms of anxiety and depression (measured by the Symptom Checklist-5 (SCL-5)). The questionnairehas been linked to highly reliable official registries on SA and DP, as well as a range of sociodemographicvariables, for a ten-year follow up period. We applied logistic (DP as dependent variable) and binomialregression (SA as dependent variable) analyses to explore the relationship between musculoskeletal painand DP and SA. In the final models, we adjusted for sociodemographic factors and symptoms of anxietyand depression. Differences between twins in a pair were explored by applying fixed effect models. Allanalyses were conducted using STATA version 13.1.Results: The final sample of 7,626 twins included 3,055 complete pairs (488 monozygotic (MZ) male, 349dizygotic (DZ) male, 747 MZ female, 589 DZ female, and 882 opposite sex twin pairs) and 1,516 singletons.By the end of follow up, 181 subjects (44 men and 137 women) received DP, and 63.7% of the sample(47.4% of males and 76.0% of females) had at least one period of SA extending 16 days. Pain at any sitewas significantly associated with DP in both sexes. Any increase in the number of pain sites reported wasassociated with about a 60% increased risk for receiving DP (OR 1.6, 95% CI 1.4-1.9), and the strength ofthe association was only marginally reduced when adjusted for symptoms of mental disorders (1.4, 1.2-1.7). In the within pair analyses the effect was no longer significant, indicating possible confounding fromgenetic and shared environmental effects. As for all cause SA, musculoskeletal pain predicted SA independentlyof all measured confounders, and the results remained significant in the within pair analyses (IncidenceRate Ratio (IRR) 1.12, 95% CI 1.03-1.23).Conclusion: In young adults, musculoskeletal pain strongly predicted SA and DP for a 10 year follow-upperiod. Musculoskeletal pain was associated with higher levels of all cause SA, even within discordant MZtwin pairs. Our results indicate that interventions to prevent musculoskeletal pain in young adults canreduce levels of SA and DP.

Efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline in Twin Families (VIPP-Twins): Study protocol for a randomized controlled trial.

BackgroundIntervention programs with the aim of enhancing parenting quality have been found to be differentially effective in decreasing negative child outcomes such as externalizing behavioral problems, resulting in modest overall effect sizes. Here we present the protocol for a randomized controlled trial to examine the efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline for Twin Families (VIPP-Twins) on parenting quality and children’s behavioral control and social competence. In addition, we aim to test the differential susceptibility theory; we examine differential efficacy of the intervention based on genetic make-up or temperament for both parents and children. Lastly, we explore neurobiological mechanisms underlying intervention effects on children’s developmental outcomes.Methods/designThe original VIPP-SD was adapted for use in families with twins. The VIPP-Twins consists of five biweekly sessions in which the families are visited at home, parent-child interactions are videotaped and parents receive positive feedback on selected video fragments. Families (N = 225) with a same sex twin (mean age = 3.6 years) were recruited to participate in the study. The study consists of four assessments. After two baseline assessments in year 1 and year 2, a random 40 % of the sample will receive the VIPP-Twins program. The first post-test assessment will be carried out one month after the intervention and there will be a long term follow-up assessment two years after the intervention. Measures include observational assessments of parenting and children’s social competence and behavioral control, and neurobiological assessments (i.e., hormonal functioning and neural (re-)activity).DiscussionResults of the study will provide insights in the efficacy of the VIPP-Twins and reveal moderators and mediators of program efficacy. Overall the randomized controlled trial is an experimental test of the differential susceptibility theory.Trial registrationDutch Trial Register: NTR5312; Date registered: July 20, 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s40359-016-0139-y) contains supplementary material, which is available to authorized users.