Incorporating genetic data from diverse populations is crucial for understanding genetic contributions to diseases and ensuring health equity in healthcare practices. However, existing reference panels either capture a limited number of populations or have small sample sizes. We examine the UK Biobank’s performance as a reference for clustering genetically similar individuals. Leveraging data from participants of diverse origins, we aim to improve population representation and mitigate bias caused by the limited number of populations in other reference panels. We combined countries of birth and ethnic backgrounds data fields from the UK Biobank and genetic information to infer genetically similar population labels. A random forest model was then trained on genetic principal components to identify each individual’s most genetically similar population. The model’s performance was validated using the 1000 Genomes and the CARTaGENE biobank data. We identified more diverse reference populations than present in datasets such as 1000 Genomes, covering 19 populations worldwide. Our model achieved medium to high precision and recall for most labeled populations, although lower rates were observed in closely related groups. For instance, we identified 519 people in CARTaGENE most genetically similar to the Middle Eastern reference sample derived in the UK Biobank (there are no Middle Eastern samples in 1000 Genomes), yielding an 81.1% precision and a 97.0% recall rate compared to demographic-based information. This practical approach of clustering genetically similar individuals utilizing existing biobank data may facilitate downstream analyses, such as genomewide association studies or polygenic risk scores in underrepresented populations in genetic studies.

Although financial stressors are implicated as risk factors for suicidal behavior, these associations might be confounded by other factors. Furthermore, a move toward high-risk subgroup definition is necessary. The authors used Swedish national registry data to examine the associations between receipt of social welfare, unemployment benefits, or early retirement (N = 627,745−2,260,753) with suicidal behavior in Cox proportional hazards models. They applied co-relative models to improve causal inference, and examined interactions with aggregate genetic risk for suicidality. All three exposures were associated with elevated suicidal behavior risk. Initial hazard ratios for suicide attempt ranged from 1.37−3.86, were similar for suicide death, and declined after controlling for psychopathology and time elapsed after exposure. Age at registration differentially impacted risk of suicidal behavior. Aggregate genetic liability for suicidality was associated with risk, but its effect was not moderated by financial stress. Financial stressors are associated with suicidal behavior risk even after controlling for psychopathology. Associations are attributable in part to familial confounding, though a potentially causal pathway was observed in most cases. Suicidality risk varied as a function of sex and age at exposure; these findings could be used to identify subgroups at high risk who warrant targeted prevention.

Most twin registries have not systematically collected the data required to determine gender identity, which has limited opportunities to evaluate potential familial contributors to gender diversity. This study addresses this gap by analyzing responses to gender identity questions introduced in Twins Research Australia’s 2023 survey. Among 4475 respondents (mean age 52.2 years, SD = 15.3), 36 (0.8%) indicated a transgender or gender diverse identity, which is consistent with population-based estimates of gender diversity internationally. Gender diversity co-occurred in 2/19 monozygotic pairs and 0/8 dizygotic pairs, giving rise to tetrachoric correlations of 0.62 (95% CI [0.33, 0.87]) and 0.00 (95% CI [0.00, 0.88]), respectively. These results broadly align with previous concordance estimates from twin studies that were specifically focused on gender identity. Although limited by a small sample size, these findings demonstrate the feasibility and utility of systematically collecting gender identity data through routine twin registry surveys.

Despite the decline in mortality rates among children in developing countries, disparities persist between countries, particularly between twins and singletons. This study employed data from nine Demographic and Health Surveys in the Dominican Republic and Haiti to estimate and compare mortality rates for twins and singletons in categories of the under-5 age group (neonatal, postneonatal, and child mortality) and examine the factors associated with excess mortality among twins. From 1996 to 2013, the under-5 mortality rate (U5MR) for singletons in the Dominican Republic declined from 56‰ (95% CI [47, 64) to 30‰ (22–39) and from 108‰ (53–164) to 53‰ (16–89) among twins. In Haiti, between 1994 and 2016, the U5MR declined from 121‰ (109–133) to 77‰ (68–80) for singletons and from 432‰ (327–538) to 204‰ (149–260) among twins. The adjusted risk of neonatal death for twins is 1.4 (1.0–1.9) times higher than for singletons in the Dominican Republic, compared to a risk of 4.3 (3.5–5.3) times higher in Haiti. In the post-neonatal period, the mortality risk for twins in the Dominican Republic was 1.8 (1.0–3.1) times higher than that for singletons, 2.9 (2.3–3.8) in Haiti. The risk of death for twins was not significantly different from that for singletons in both the Dominican Republic and Haiti at ages 1–4 years. Low birth weight, lack of breastfeeding, absence of, or inadequate, antenatal care, noncesarean section birth, and high birth order were associated with excess mortality among twins in both countries.

The objective of this study was to to describe perinatal outcomes in monochorionic twin pregnancies after selective fetal reduction using bipolar cord coagulation (BCC) or interstitial laser ablation (ILA). This retrospective cohort study included monochorionic twin pregnancies requiring selective fetal reduction between 2008 and 2023 at a referral center in Spain. Maternal and perinatal data were collected and analyzed to compare outcomes between BCC and ILA techniques. The primary outcome was the survival of the co-twin, while secondary outcomes included gestational age at delivery, the incidence of PPROM, birth weight and long-term neurodevelopmental outcomes. Eighty-four procedures were performed (30 ILA, 54 BCC). The overall co-twin survival rate was 80%, with BCC showing a higher survival rate (87%) compared to ILA (67%, p = .026). Fetal death before 24 weeks was more common in ILA (30%) than BCC (7.4%, p = .010). The mean gestational age at delivery was lower in BCC (36.6 weeks) than ILA (38.6 weeks, p = .021), and preterm delivery was more frequent in BCC (50%) compared to ILA (14%, p = .005). BCC seems to have a better overall survival than ILA in complicated monochorionic twins’ selective terminations. However, we could not clarify whether this difference was due to the technique itself or the different gestational age at the time of the procedure as well as the specific indication.

Vanishing twin syndrome is a miscarriage of multiples where one or more fetuses ‘vanishes’ (i.e., partial or full resorption or via calcification) during pregnancy, often before detection via ultrasound. It affects 30−50% of multifetal pregnancies, with most cases resulting in full resorption within the first trimester. Despite its recognition since 1945 and rising occurrence in both natural and assisted pregnancies, standardized clinical guidelines remain inadequate, leading to inconsistent diagnosis, counseling, and communication from healthcare providers. This study examines the experiences of mothers and gestational carriers diagnosed with VTS, focusing on patient-provider communication, risks, and symptom disclosure. A global online survey collected qualitative and quantitative data from 153 participants across 17 countries. Results show that most patients with formal diagnoses experienced negative interactions with healthcare providers, with an average sentiment score of −0.7 (on a scale from −2 to 2). Over 53.4% rated their communication experience as −1, and the average satisfaction score for the amount of information received was 3.5/10. Additionally, 43% of respondents were not informed about chorionicity, a key factor affecting fetal outcomes. Significant discrepancies in care were observed across different countries. The findings highlight major gaps in patient-provider communication and inconsistent clinical practices regarding VTS. Addressing these issues through improved education, clearer protocols, and standardized guidelines could enhance patient experiences and decision-making. Future research should focus on provider training and evidence-based strategies to improve the management of VTS and other types of miscarriage and death of multiples during pregnancy and postpartum.

Although it is well established that gestational diabetes mellitus (GDM) is associated with fetal overgrowth in singleton pregnancies, little is known about its role in twins. We aimed to explore the relationship between GDM and the longitudinal fetal growth in twin pregnancies. This was a retrospective matched cohort study of GDM and non-GDM twin pregnancies delivered ≥36 weeks without other complications. All the women performed ≥3 ultrasounds after 22 weeks. Linear mixed models (LMMs) were used to explore the relationships between longitudinal fetal growth trajectories and GDM. Group-based trajectory modeling (GBTM) and generalized estimating equation (GEE) were applied to identify the latent growth patterns and investigate their relationships with GDM. In total, 215 GDM and 645 non-GDM twins were included, the majority of the patients did not require medication therapy (n = 202, GDMA1). LMM revealed that, compared with non-GDM, GDM was associated with an average increase in fetal weight of 4.36 g (95% CI [1.25, 7.48]) per week. GBTM and GEE further revealed that GDM increased the odds of fetal weight trajectory to nearly 40% of the total fetal weight trajectory, classified into the high-speed group (aOR = 1.39, 95% CI [1.03, 1.88]), associating with a 49.44 g (95% CI [11.41, 87.48]) increase in birth weight. Subgroup analysis revealed that all these differences were only significant among the GDMA1 pregnancies (p < .05). GDM (GDMA1) is significantly associated with an increase in fetal weight during gestation in twin pregnancies. However, this acceleration is mild, and its significance requires further exploration.

Twins have been popular figures in many fictional works. A review of two well-known twin-based series, and why they fascinate, is presented. This summary is followed by reviews of twinning in low-income countries, oxytocin administration during twin pregnancies, male-female twins and maternal risk of preeclampsia, and the loss of a twin from the controversial 1960s New York City twin study. The final part of this column covers human interest stories involving twins, specifically a monozygotic quadruplet set conceived naturally, the twins born to Cleopatra and Mark Antony, a star basketball player with a twin brother, a twin stabbed at a track meet, and the revelation of another twin hostage held in Gaza.