Pregnancy outcomes of monochorionic diamniotic and dichorionic diamniotic twin pregnancies conceived by assisted reproductive technology and conceived naturally: a study based on chorionic comparison.

OBJECTIVE: To evaluate monochorionic diamniotic (MCDA) and dichorionic diamniotic (DCDA) twin pregnancies conceived by assisted reproductive technology (ART) and conceived naturally. METHODS: We retrospectively analyzed the data on twin pregnancies conceived by ART from January 2015 to January 2022,and compared pregnancy outcomes of MCDA and DCDA twins conceived by ART with those of MCDA and DCDA twins conceived naturally, pregnancy outcomes between MCDA and DCDA twins conceived by ART, and pregnancy outcomes of DCT and TCT pregnancies reduced to DCDA pregnancies with those of DCDA pregnancies conceived naturally. RESULT: MCDA pregnancies conceived by ART accounted for 4.21% of the total pregnancies conceived by ART and 43.81% of the total MCDA pregnancies. DCDA pregnancies conceived by ART accounted for 95.79% of the total pregnancies conceived by ART and 93.26% of the total DCDA pregnancies. Women with MCDA pregnancies conceived by ART had a higher premature delivery rate, lower neonatal weights, a higher placenta previa rate, and a lower twin survival rate than those with MCDA pregnancies conceived naturally (all p < 0.05). Women with DCDA pregnancies conceived naturally had lower rates of preterm birth, higher neonatal weights, and higher twin survival rates than women with DCDA pregnancies conceived by ART and those with DCT and TCT pregnancies reduced to DCDA pregnancies (all p < 0.05). CONCLUSION: Our study confirms that the pregnancy outcomes of MCDA pregnancies conceived by ART are worse than those of MCDA pregnancies conceived naturally. Similarly, the pregnancy outcomes of naturally-conceived DCDA pregnancies are better than those of DCDA pregnancies conceived by ART and DCT and TCT pregnancies reduced to DCDA pregnancies.

The Population-Based Hungarian Twin Registry: An Update.

Between 2006 and 2021, the Hungarian Twin Registry (HTR) operated a volunteer twin registry of all age groups (50% monozygotic [MZ], 50% dizygotic [DZ], 70% female, average age 34 ± 22 years), including 1044 twin pairs, 24 triplets and one quadruplet set. In 2021, the HTR transformed from a volunteer registry into a population-based one, and it was established in the Medical Imaging Centre of Semmelweis University in Budapest. Semmelweis University's innovation fund supported the development of information technology, a phone bank and voicemail infrastructure, administrative materials, and a new website was established where twins and their relatives (parent, foster parent or caregiver) can register. The HTR's biobank was also established: 157,751 individuals with a likely twin-sibling living in Hungary (77,042 twins, 1194 triplets, 20 quadruplets, and one quintuplet) were contacted between February and March of 2021 via sealed letters. Until November 20, 2022, 12,001 twin individuals and their parents or guardians (6724 adult twins, 3009 parents/guardians and 5277 minor twins) registered, mostly online. Based on simple self-reports, 37.6% of the registered adults were MZ twins and 56.8% were DZ; 1.12% were triplets and 4.5% were unidentified. Of the registered children, 22.3% were MZ, 72.7% were DZ, 1.93% were triplets, and 3.05% were unidentified. Of the registered twins, 59.9% were female (including both the adult and minor twins). The registration questionnaire consists of eight parts, including socio-demographic and anthropometric data, smoking habits and medical questions (diseases, operations, therapies). Hungary's twin registry has become the sole and largest population-based twin registry in Central Eastern Europe. This new resource will facilitate performing world-class modern genetic research.

TwinsMX: Exploring the Genetic and Environmental Influences on Health Traits in the Mexican Population.

TwinsMX registry is a national research initiative in Mexico that aims to understand the complex interplay between genetics and environment in shaping physical and mental health traits among the country's population. With a multidisciplinary approach, TwinsMX aims to advance our knowledge of the genetic and environmental mechanisms underlying ethnic variations in complex traits and diseases, including behavioral, psychometric, anthropometric, metabolic, cardiovascular and mental disorders. With information gathered from over 2800 twins, this article updates the prevalence of several complex traits; and describes the advances and novel ideas we have implemented such as magnetic resonance imaging. The future expansion of the TwinsMX registry will enhance our comprehension of the intricate interplay between genetics and environment in shaping health and disease in the Mexican population. Overall, this report describes the progress in the building of a solid database that will allow the study of complex traits in the Mexican population, valuable not only for our consortium, but also for the worldwide scientific community, by providing new insights of understudied genetically admixed populations.

Tissue-specific nonheritable influences drive endometrial immune system variation.

Although human twin studies have revealed the combined contribution of heritable and environmental factors in shaping immune system variability in blood, the contribution of these factors to immune system variability in tissues remains unexplored. The human uterus undergoes constant regeneration and is exposed to distinct environmental factors. To assess uterine immune system variation, we performed a system-level analysis of endometrial and peripheral blood immune cells in monozygotic twins. Although most immune cell phenotypes in peripheral blood showed high genetic heritability, more variation was found in endometrial immune cells, indicating a stronger influence by environmental factors. Cytomegalovirus infection was identified to influence peripheral blood immune cell variability but had limited effect on endometrial immune cells. Instead, hormonal contraception shaped the local endometrial milieu and immune cell composition with minor influence on the systemic immune system. These results highlight that the magnitude of human immune system variation and factors influencing it can be tissue specific.

Heritability of Gene Expression Measured from Peripheral Blood in Older Adults.

The contributions of genetic variation and the environment to gene expression may change across the lifespan. However, few studies have investigated the heritability of blood gene expression in older adults. The current study therefore aimed to investigate this question in a community sample of older adults. A total of 246 adults (71 MZ and 52 DZ twins, 69.91% females; mean age-75.79 ± 5.44) were studied. Peripheral blood gene expression was assessed using Illumina microarrays. A heritability analysis was performed using structural equation modelling. There were 5269 probes (19.9%) from 4603 unique genes (23.9%) (total 26,537 probes from 19,256 genes) that were significantly heritable (mean h2 = 0.40). A pathway analysis of the top 10% of significant genes showed enrichment for the immune response and ageing-associated genes. In a comparison with two other gene expression twin heritability studies using adults from across the lifespan, there were 38 out of 9479 overlapping genes that were significantly heritable. In conclusion, our study found ~24% of the available genes for analysis were heritable in older adults, with only a small number common across studies that used samples from across adulthood, indicating the importance of examining gene expression in older age groups.

Heritability of Clinically Diagnosed Obsessive-Compulsive Disorder Among Twins.

This cohort study estimates the heritability of clinically diagnosed obsessive-compulsive disorder in a sample of twins.

Second twin outcome at birth: retrospective analysis in a single tertiary centre in Malaysia.

OBJECTIVES: To investigate factors associated with outcome of second twin during labour. METHODS: The study was a retrospective cohort study in a single tertiary centre in Malaysia from 2014 until 2018 involving all twin pregnancies delivered at or more than 24 weeks of gestation. RESULTS: Total of 409 twin pregnancies were included. Dichorionic twin comprises of 54.5 % (n=223) and 45.5 % (n=186) are monochorionic. Women with dichorionic pregnancies are significantly older (p<0.001), have more pre-existing medical disorders (p=0.011) and fetal structural anomalies (p=0.009). Monochorionic pregnancies are significantly more amongst Malay (p=0.01) and conceived spontaneously (p<0.001). There are significantly more fetuses both in cephalic presentation (p=0.026), birthweight discrepancy more than 20 % (p=0.038) and shorter mean inter-twin delivery duration (p=0.048) in monochorionic pregnancies. Second twin delivered with Apgar score <7 is significantly more in dichorionic pregnancies (p=0.006). The second twin is associated with lower birthweight, small for gestational age and arterial cord pH<7.25. Within the group of women who delivered both fetuses vaginally, there was significantly more second twins with intertwin delivery duration less than 30 min who were delivered vaginally without instrumentation (p=0.018). There was significantly more second twin with intertwin delivery duration of 30 min and more with arterial cord pH<7.25 (p=0.045). Those who delivered spontaneously had inter-twin delivery duration within 15-29 min. The outcome of second twin is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth. CONCLUSIONS: The neonatal outcome for the second twin at birth is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth in a cohort managed with non-active management of the second twin in Malaysia.

Common genetic factors for uncontrolled eating mechanisms.

OBJECTIVE: Reward-based eating drives are putative mechanisms of uncontrolled eating implicated in obesity and disordered eating (e.g., binge eating). Uncovering the genetic and environmental contributions to reward-related eating, and their genetic correlation with BMI, could shed light on key mechanisms underlying eating and weight-related disorders. METHOD: We conducted a classical twin study to examine how much variance in uncontrolled eating phenotypes and body mass index (BMI) was explained by genetic factors, and the extent that these phenotypes shared common genetic factors. 353 monozygotic twins and 128 dizygotic twins completed the Reward-based Eating Drive 13 scale, which measures three distinct uncontrolled eating phenotypes (loss of control over eating, preoccupation with thoughts about food, and lack of satiety), and a demographic questionnaire which included height and weight for BMI calculation. We estimated additive genetic (A), common environmental (C), and unique environmental (E) factors for each phenotype, as well as their genetic correlations, with a multivariate ACE model. A common pathway model also estimated whether genetic variance in the uncontrolled eating phenotypes was better explained by a common latent uncontrolled eating factor. RESULTS: There were moderate genetic correlations between uncontrolled eating phenotypes and BMI (.26-.41). Variance from the uncontrolled eating phenotypes was also best explained by a common latent uncontrolled eating factor that was explained by additive genetic factors (52%). DISCUSSION: These results suggest that uncontrolled eating phenotypes are heritable traits that also share genetic variance with BMI. This has implications for understanding the cognitive mechanisms that underpin obesity and disordered eating. PUBLIC SIGNIFICANCE: Our study clarifies the degree to which uncontrolled eating phenotypes and BMI are influenced by shared genetics and shows that vulnerability to uncontrolled eating traits is impacted by common genetic factors.

Using Polygenic Scores for Circadian Rhythms to Predict Wellbeing, Depressive Symptoms, Chronotype, and Health.

The association between circadian rhythms and diseases has been well established, while the association with mental health is less explored. Given the heritable nature of circadian rhythms, this study aimed to investigate the relationship between genes underlying circadian rhythms and mental health outcomes, as well as a possible gene-environment correlation for circadian rhythms. Polygenic scores (PGSs) represent the genetic predisposition to develop a certain trait or disease. In a sample from the Netherlands Twin Register (N = 14,021), PGSs were calculated for two circadian rhythm measures: morningness and relative amplitude (RA). The PGSs were used to predict mental health outcomes such as subjective happiness, quality of life, and depressive symptoms. In addition, we performed the same prediction analysis in a within-family design in a subset of dizygotic twins. The PGS for morningness significantly predicted morningness (R2 = 1.55%) and depressive symptoms (R2 = 0.22%). The PGS for RA significantly predicted general health (R2 = 0.12%) and depressive symptoms (R2 = 0.20%). Item analysis of the depressive symptoms showed that 4 out of 14 items were significantly associated with the PGSs. Overall, the results showed that people with a genetic predisposition of being a morning person or with a high RA are likely to have fewer depressive symptoms. The four associated depressive symptoms described symptoms related to decision-making, energy, and feeling worthless or inferior, rather than sleep. Based on our findings future research should include a substantial role for circadian rhythms in depression research and should further explore the gene-environment correlation in circadian rhythms.

Exploring Hematological and Biochemical Disparities in Same-Sex and Opposite-Sex Females: A Cross-Sectional Twin Study in a Ghanaian Population.

There are sex-dependent differences in hematological and biochemical variables in adulthood attributed to the predominant effects of testosterone in males and estrogen in females. The Twin Testosterone Transfer (TTT) hypothesis proposes that opposite-sex females may develop male-typical traits due to exposure to relatively higher levels of prenatal testosterone than same-sex females. Additionally, prenatal testosterone exposure has been suggested as a correlate of current circulating testosterone levels. Consequently, opposite-sex females might exhibit male-typical patterns in their hematological and biochemical variables. Despite this hypothesis, routine laboratory investigations assign the same reference range to all females. Our cross-sectional study, conducted in Tamale from January to September 2022, included 40 twins, comprising 10 opposite-sex (OS) males (25%), 10 OS females (25%), and 20 same-sex (SS) females (50%), all aged between 18 and 27 years. Fasting venous blood samples were collected and analyzed using automated hematology and biochemistry laboratory analyzers. Results indicated that levels of hemoglobin, serum creatinine, gamma-glutamyl transferase, total protein, globulins, and total testosterone were significantly higher in OS males than OS females. Conversely, total cholesterol and low-density lipoprotein cholesterol were significantly higher in OS females than OS males. Unexpectedly, levels of low-density lipoprotein cholesterol and total testosterone were significantly higher in SS females than OS females. Contrary to expectations, opposite-sex females did not exhibit male-typical patterns in their hematological and biochemical variables. This suggests that the TTT effect may not occur or may not be strong enough to markedly affect hematological and biochemical variables in OS females.

Adverse Childhood Experiences and Adult Mental Health Outcomes.

Importance: Exposure to adverse childhood experiences (ACEs) has consistently been associated with multiple negative mental health outcomes extending into adulthood. However, given that ACEs and psychiatric disorders cluster within families, it remains to be comprehensively assessed to what extent familial confounding contributes to associations between ACEs and clinically confirmed adult psychiatric disorders. Objective: To investigate whether associations between ACEs and adult mental health outcomes remain after adjusting for familial (genetic and environmental) confounding. Design, Setting, and Participants: This Swedish twin cohort study used a discordant twin pair design based on monozygotic (MZ) and dizygotic (DZ) twins. A total of 25 252 adult twins (aged 18-47 years) from the Swedish Twin Registry born between 1959 and 1998 were followed up from age 19 years until 2016, with a maximum follow-up time of 39 years. Data were analyzed from April 2022 to November 2023. Exposures: A total of 7 ACEs, including family violence, emotional abuse or neglect, physical neglect, physical abuse, sexual abuse, rape, and hate crime, were assessed with items from the Life Stressor Checklist-Revised in a web-based survey. Main Outcomes and Measures: Adult (ages >18 years) clinical diagnosis of psychiatric disorders (ie, depressive, anxiety, alcohol or drug misuse, or stress-related disorders) were obtained from the Swedish National Patient Register. Results: Of 25 252 twins included in the study (15 038 female [59.6%]; mean [SD] age at ACE assessment, 29.9 [8.7] years), 9751 individuals (38.6%) reported exposure to at least 1 ACE. A greater number of ACEs was associated with increased odds of any psychiatric disorder in the full cohort (odds ratio [OR] per additional ACE, 1.52; 95% CI, 1.48-1.57). The association remained but ORs per additional ACE were attenuated in DZ (1.29; 95% CI, 1.14-1.47) and MZ (1.20; 95% CI, 1.02-1.40) twin pairs. Individuals who were exposed to sexual abuse compared with those who were not exposed had increased odds of any clinically confirmed psychiatric disorder in all comparisons: full cohort (OR, 3.09; 95% CI, 2.68-3.56), DZ twin pairs (OR, 2.10; 95% CI, 1.33-3.32), and MZ twin pairs (1.80; 95% CI, 1.04-3.11). Conclusions and relevance: This study found that associations between ACEs and adult mental health outcomes remained after controlling for shared genetic and environmental factors, which was particularly evident after multiple ACEs or sexual abuse. These findings suggest that targeted interventions may be associated with reduced risks of future psychopathology.

Can flow proneness be protective against mental and cardiovascular health problems? A genetically informed prospective cohort study.

Flow is a phenomenon where one experiences optimal challenge, marked by an intense, effortless, and rewarding concentration on a task. Past research shows that flow proneness is associated with good mental and cardiovascular health. However, this research has been primarily cross-sectional, based on self-report data, and has not controlled for potential confounding effects of neuroticism. In a large, longitudinal twin sample (N = 9361), we used nationwide patient registry data to test whether flow proneness predicted registry-based diagnoses of depression, anxiety, schizophrenia, bipolar disorder, stress-related disorders, or cardiovascular diseases. We used survival analyses taking time to diagnosis into account to test if (a) there is a relationship between flow proneness and health diagnoses over time, (b) neuroticism confounds this relationship, and (c) the relationship remains present within discordant monozygotic twin pairs (N = 952), thereby controlling for genetic and shared environmental confounding. Individuals with higher flow proneness had a decreased risk of receiving diagnoses for depression (16%; CI [14%, 18%]), anxiety (16%; CI [13%, 18%]), schizophrenia (15%; CI [4%, 25%]), bipolar (12%; CI [6%, 18%]), stress-related (9%; CI [9%, 12%]), and cardiovascular disorders (4%; CI [1%, 8%]). When controlling for neuroticism, higher flow proneness still decreased the risk of depression (6%; CI [3%, 9%]) and anxiety diagnoses (5%; CI [1%, 8%]). Monozygotic twins who experienced more flow than their co-twin had a lower risk for depression (16%; CI [5%, 26%]) and anxiety (13%; CI [1%, 24%]), though only the association with depression remained significant when also controlling for neuroticism (13%; CI [1%, 24%]). Findings are in line with a causal protective role of flow experiences on depression and potentially anxiety and highlight that neuroticism and familial factors are notable confounding factors in observed associations between flow proneness and health outcomes.

Heritability of tear fluid cytokines in healthy twins.

PURPOSE: Ocular surface disease is common and it is associated with elevated concentration levels of cytokines in tear fluid. Studies of the normal variation in tear fluid inflammatory markers are lacking. New knowledge may help guide research into ocular surface disease biomarkers and therapeutics. METHODS: In this prospective twin cohort study, healthy individuals were recruited from a population-based registry. Tear fluid was collected with the Schirmer test strips was submerged in phosphate buffered saline and stored at -80° before undergoing 27-cytokine multiplex immunoassay analysis. Broad-sense heritability (h2) of cytokine concentrations was analyzed. RESULTS: 90 participants (23 monozygotic and 22 dizygotic twin pairs) were included. Data availability allowed for heritability analysis of 15 cytokines, and a h2 >50% was seen for 10 cytokines. A statistical power of >80% was achieved for heritability analyses of the cytokines interferon gamma induced protein 10 (h2 = 94.8%), eotaxin (89.8%), interleukin 7 (86.6%), interleukin 1ß (82.2%) and monocyte chemoattractant protein 1 (68.2%). CONCLUSIONS: The tear fluid concentration of several analyzed cytokines was found to be highly heritable. A considerable amount of the inter-individual variation observed for the concentration of certain tear fluid cytokines can be linked to hereditary factors that cannot easily be modified by changing factors in the environment of patients. This suggests that a higher success in ocular surface disease drug discovery may be anticipated for drugs that have targets in specific populations, and points to the importance of emphasizing known preventive measures of ocular surface disease and examinations of close relatives of patients with ocular surface disease, such as dry eye disease.

Surgically Treated Degenerative Lumbar Spine Diseases in Twins.

BACKGROUND: There is growing evidence to suggest a potential genetic component underlying the development and progression of lumbar spine diseases. However, the heritability and the concordance rates for the phenotypes requiring surgery for the common spine diseases lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH) are unknown. The aim of this study was to determine the heritability and the concordance rates for LSS and LDH requiring surgery by studying monozygotic (MZ) and dizygotic (DZ) twin pairs. METHODS: Patients between 18 and 85 years of age who underwent surgery for LSS or LDH between 1996 and 2022 were identified in the national Swedish spine registry (LSS: 45,110 patients; LDH: 39,272 patients), and matched with the Swedish Twin Registry to identify MZ and DZ twins. Pairwise and probandwise concordance rates, heritability estimates, and MZ/DZ concordance ratios were calculated. RESULTS: We identified 414 twin pairs (92 MZ and 322 DZ pairs) of whom 1 or both twins underwent surgery for LSS. The corresponding number for LDH was 387 twin pairs (118 MZ and 269 DZ pairs). The probandwise concordance rate for LSS requiring surgery was 0.25 (26 of 105) (95% confidence interval [CI], 0.14 to 0.34) for MZ twins and 0.04 (12 of 328) (95% CI, 0.01 to 0.07) for DZ twins. The corresponding values for LDH requiring surgery were 0.03 (4 of 120) (95% CI, 0 to 0.08) and 0.01 (4 of 271) (95% CI, 0 to 0.04), respectively. The probandwise MZ/DZ concordance ratio was 6.8 (95% CI, 2.9 to 21.5) for LSS and 2.3 (95% CI, 0 to 8.9) for LDH. The heritability was significantly higher in LSS compared with LDH (0.64 [95% CI, 0.50 to 0.74] versus 0.19 [95% CI, 0.08 to 0.35]). CONCLUSIONS: Our findings suggest that genetic factors may play an important role in the risk of developing LSS requiring surgery, whereas heredity seems to be of less importance in LDH requiring surgery. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Surgically treated degenerative disk disease in twins.

PURPOSE: Previous studies have suggested that genetic factors are important in the development of degenerative disk disease (DDD). However, the concordance rates for the phenotypes requiring surgery are unknown. The purpose of this study was to determine the concordance rates for DDD requiring surgery by studying monozygotic (MZ) and dizygotic (DZ) twin pairs. METHODS: Patients, aged between 18 and 85 years, operated for DDD between 1996 and 2022 were identified in the national Swedish spine register (Swespine) and matched with the Swedish twin registry (STR) to identify MZ and DZ twins. Pairwise and probandwise concordance rates were calculated. RESULTS: We identified 11,207 patients, 53% women, operated for DDD. By matching the Swespine patients with the STR, we identified 121 twin pairs (37 MZ and 84 DZ) where one or both twins were surgically treated for DDD. The total twin incidence for operated DDD was 1.1%. For DDD requiring surgery, we found no concordant MZ pair and no concordant DZ pair where both twins were operated for DDD. When we evaluated pairs where at least one twin was operated for DDD, we found two concordant MZ pairs (the co-twins were operated for spinal stenosis) and two  concordant DZ pairs (one co-twin operated for spinal stenosis and one (co-twin operated for disk herniation). CONCLUSIONS: Our findings suggest that genetic factors are probably not a major etiologic component in most cases of DDD requiring surgery. The findings of this study can be used for counseling patients about the risk for requiring DDD surgery.

Selective feticide in dichorionic diamniotic (DCDA) twins complicated with previable premature rupture of membrane before 24 weeks may be a safe therapeutic alternative to ongoing pregnancy.

BACKGROUND: To date, there are no clinical guidelines for dichorionic diamniotic (DCDA) twins complicated with previable premature rupture of membrane (PV-ROM) before 24 weeks of gestation. The typical management options including expectant management and/or pregnant termination, induce the risks of fetal mortality and morbidity. OBJECTIVE: To explore the feasibility selective feticide in DCDA twins complicated with PV-ROM. STUDY DESIGN: A Retrospective cohort study, enrolling 28 DCDA twins suffering from PV-ROM in a tertiary medical center from Jan 01 2012 to Jan 01 2022. The obstetric outcome was compared between selective feticide group and expectant management group. RESULTS: There were 12 cases managed expectantly and 16 underwent selective feticide. More cases suffered from oligohydramnios in expectant management group compared to selective feticide group (P = 0.008). Among 13 cases with ROM of upper sac, the mean gestational age at delivery was (33.9 ± 4.9) weeks in the selective feticide group, which was significantly higher than that in the expectant management (P = 0.038). Five fetuses (83.3%) with selective feticide delivered after 32 weeks, whereas only one (14.3%) case in expectant management group (P = 0.029). However, in the subgroup with ROM of lower sac, no significant difference of the mean gestation age at delivery between groups and none of cases delivered after 32 weeks. CONCLUSION: There was a trend towards an increase in latency interval in DCDA twins with PV-ROM following selective feticide, compared to that with expectant management. Furthermore, selective feticide in cases with PV-ROM of upper sac has a favorable outcome.

Twin studies as an innovative approach to address research questions in cancer care within primary care settings.

This paper proposes the utilisation of twin studies as a novel and powerful methodological approach to investigate critical research questions pertaining to cancer prevention, screening, diagnosis, treatment and survivorship within primary care contexts. The inherent genetic similarity between monozygotic (MZ) (identical) twins provides a unique opportunity to disentangle genetic and environmental influences on cancer-related outcomes. MZ twins share virtually identical genetic makeup, offering a unique opportunity to discern the relative contributions of genetic and environmental factors to cancer-related outcomes. In contrast, dizygotic (DZ) twins, also known as fraternal twins, develop from two separate eggs fertilised by two different sperm and share on average 50% of their genetic material, the same level of genetic similarity found in non-twin siblings. Comparisons between MZ and DZ twins enable researchers to disentangle hereditary factors from shared environmental influences. This methodology has the potential to advance our understanding of the multifaceted interplay between genetic predisposition, lifestyle factors and healthcare interventions in the context of cancer care. This paper outlines the rationale, design considerations and potential applications of twin studies in primary care-based cancer research.

Family History of Twinning and Fertility Traits in Nigerian Mothers of Dizygotic Twins.

Familial twinning and fertility traits were investigated in Nigerian mothers of dizygotic (DZ) twins (MoDZT; N = 972) and controls (N = 525) who responded to our person-to-person interview, which included questions on pregnancy history and family history of DZ twinning. Controls were defined as women who are not twins themselves and do not have twins in their first-degree relatives. Over 95% of the participants were Yoruba. We found that Nigerian MoDZT had an average of 4.0 (±2.6) pairs of twins among their relatives, and of these, the prevalence of DZ twins was significantly higher than that of monozygotic (MZ) twins (45.9% vs. 25.8%). Controls had an average of 0.5 (±0.4) pairs, and over 95% of the controls had no twins in their relatives. These results suggest genetic influences on DZ twinning in Nigerians. MoDZT were significantly younger in their mean age at first child, and had higher parity than controls, suggesting increased fertility in MoDZT. As compared to mothers with a single set of twins, mothers (N = 130) with multiple sets had significantly more twins among their relatives (5.4 pairs vs. 3.7 pairs) and had their first twins at a younger age (28.4 vs. 30.7 years), indicating that mothers with multiple sets of twins might have higher genetic propensity for twinning associated with earlier age at twin pregnancy. Our findings argue for genomewide association studies for DZ twinning in Nigerians, and may help to develop intervention strategies to overcome infertility/subfertility problems.

Predictive value of maternal serum placental growth factor levels for discordant fetal growth in twins: a retrospective cohort study.

BACKGROUND: Accurate prenatal recognition of discordant fetal growth in twins is critical for deciding suitable management strategies. We explored the predictive value of the level of maternal second-trimester placental growth factor (PLGF) as a novel indicator of discordant fetal growth. METHODS: A total of 860 women pregnant with twins were enrolled, including 168 women with monochorionic twins (31 cases of discordant fetal growth and 137 without) and 692 with dichorionic twins (79 cases of discordant fetal growth and 613 without). Maternal second-trimester PLGF concentrations were measured via immunofluorescence. RESULTS: Maternal second-trimester PLGF levels were significantly lower in women pregnant with twins who subsequently developed discordant fetal growth than in those who did not (monochorionic twin pregnancy: P < 0.001; dichorionic twin pregnancy: P < 0.001). A 3-4 fold difference in median PLGF concentrations was detected between the two groups with both monochorionic and dichorionic twin pregnancies. Maternal second-trimester PLGF levels were significantly correlated with birth weight differences (monochorionic twin pregnancy: r = - 0.331, P < 0.001; dichorionic twin pregnancy: r = - 0.234, P < 0.001). A receiver operating characteristic curve was used to evaluate the predictive efficiency. In monochorionic twin pregnancies, the area under the curve (AUC) was 0.751 (95% confidence interval [CI]: 0.649-0.852), and the cutoff value was 187.5 pg/mL with a sensitivity of 77.4% and specificity of 71.0%. In dichorionic twin pregnancies, the AUC was 0.716 (95% CI; 0.655-0.777), and the cutoff value was 252.5 pg/mL with a sensitivity of 65.1% and specificity of 69.6%. Based on the above cutoff values, univariate and multivariate logistic regression analyses were performed to calculate the odds ratios (OR) for the PLGF levels. After adjustment for potential confounding factors, low PLGF concentrations still significantly increased the risk of discordant fetal growth (monochorionic twin pregnancy: adjusted OR: 7.039, 95% CI: 2.798-17.710, P < 0.001; dichorionic twin pregnancy: adjusted OR: 4.279, 95% CI: 2.572-7.120, P < 0.001). CONCLUSIONS: A low maternal second-trimester PLGF level is considered a remarkable risk factor and potential predictor of discordant fetal growth. This finding provides a complementary screening strategy for the prediction of discordant fetal growth and offers a unique perspective for the subsequent research in this field.