Quadruplets are at elevated physical risks at prenatal, perinatal, and postnatal levels, relative to twins. A brief review of this area is followed by discussion of a female quadruplet with three co-quadruplet brothers. Next, several timely twin research reports are examined. The topics include antenatal corticosteroids and twins’ neonatal outcomes, the meaning of fatherhood in families with twins, what doppelgängers (look-alikes) reveal about physical and behavioral similarity, and monozygotic (MZ) co-twin discordance for asymmetric pigmented paravenous chorioretinal atrophy. A lawsuit involving alleged cheating on a medical school examination by identical twins is also reviewed. General interest stories cover opposite-sex twin Holocaust survivors, twin models at a Gucci fashion show, twins with different fathers, reunited female twins who entered the same convent, the death of an MZ female twin soldier during training, and the surgical separation of conjoined twins in Brazil.

The aim of this study was to describe the neonatal management and outcome in monochorionic twins with twin-to-twin transfusion syndrome (TTTS) not treated with fetoscopic laser surgery. All consecutive live-born neonates with TTTS managed at our center between 2002 and 2021 were included in this retrospective study. Neonatal outcome was assessed in 44 twin pairs with TTTS not treated with laser (nonlaser group) compared to a control group of 88 twin pairs with TTTS successfully treated with laser (laser group), matched for gestational age at birth. Primary outcome was adverse neonatal outcome, a composite outcome including neonatal mortality or severe neonatal morbidity. The incidence of adverse neonatal outcome in the nonlaser group and laser group was 30% (26/88) and 11% (19/176), respectively (relative risk = 3.46, 95% CI [1.79, 6.71]). In the nonlaser group, 11% had necrotizing enterocolitis (vs. 2% in the laser group) and 24% had hypotension (vs. 10% in the laser group). Recipients in the nonlaser group had, compared to recipients in the laser group, significantly more severe cerebral injury (18% vs. 5%) and more polycythemia at birth (21% vs. 1%). Donors in the nonlaser group had, compared to donors in the laser group, more severe growth restriction (71% vs 42%), renal failure (11% vs 1%), and anemia at birth (25% vs. 7%). Thus, the risk for neonatal mortality and/or severe morbidity is three-fold higher in TTTS not treated with laser than in TTTS treated with laser, which highlights the fact that these neonates with TTTS are very sick at birth, requiring accurate and prompt intensive treatment.

In this study, we analyzed the estimated frequency of monozygotic (MZ) and dizygotic (DZ) spontaneous twins in Lombardy during the period 2007−2017. This is a population-based study using the regional healthcare utilization databases of the Lombardy Region. The total number of spontaneous twin deliveries, in separate strata of like and unlike sex, was obtained. Moreover, estimates of DZ and MZ twin births were calculated using Weinberg’s method. The standardized rates (SRs), adjusted for maternal age, of DZ and MZ twin births were computed according to calendar period. The twinning rates were calculated among strata of parity and maternal age. Finally, DZ:MZ ratio was calculated. Among the 734,278 spontaneous deliveries, 9176 (12.5 out of 1000 births) couples of twins were identified. In the three periods considered (i.e. 2007−2010, 2011−2014 and 2015−2017), no trend in the SRs of MZ twins was observed, respectively 0.41 (95% CI [0.40, 0.43]), 0.43 (95% CI [0.42, 0.45]) and 0.43 (95% CI[0.42, 0.45]). Differently, a slightly decreasing trend was observed in DZ twins SRs, respectively 0.87 (95% CI [0.84, 0.89]), 0.81 (95% CI [0.79, 0.83]), and 0.78 (95% CI [0.76, 0.80]). As concerns parity and maternal age, the rate of DZ twin births was consistently higher in nulliparae women aged 35 years or more. In our cohort, despite the increase of maternal age, a decline of spontaneous twin births emerged, especially due to the downward trend of DZ twins.

Twin reversed arterial perfusion (TRAP) sequence is a rare anomaly in 1% of monochorionic twin pregnancies. Few TRAP sequence cases have a rudimentary heart with cardiac motion in the acardiac twins. Herein, we investigated the venous Doppler waveform in two cases of TRAP sequence with a rudimentary heart with cardiac motion in the acardiac twin. Although both cases had veno-venous anastomoses, the venous Doppler waveforms of the umbilical vein differed. A comparison of the characteristics of the cases indicated that the existence of a ductus venosus, or greater heart pulse power, in the acardiac twin might impact the venous Doppler waveform in the pump twin.

Whether assisted hatching (AH) is associated with a higher incidence of monozygotic twinning (MZT) in women undergoing assisted reproductive technology remains controversial; the aim of the study was to demonstrate the relationship between AH and MZT. A total of 8900 clinical pregnancies were selected among embryo transfer cycles from January 2011 to October 2019. Women receiving day (D) 3 embryos were divided into groups A–C: group A (n = 1651) and group B (n = 1045) included women aged ≤37 or ≥38 years, respectively, with zona pellucida (ZP) thinning; group C (n = 3865) included women aged ≤37 years without AH. Women aged ≤37 years who underwent blastocyst transfer and/or blastocyst ZP breaching were included in group D (n = 2339). The incidence of MZT was compared among groups A, B and C, and between groups C and D. The incidence of MZT in group B (2.2%) was significantly higher than in group A (1.0%), especially following intracytoplasmic sperm injection (ICSI), while the incidence of MZT in group A (1.0%) was significantly lower than in group C (2.2%). The MZT rate with in vitro fertilization was higher in group D (2.8%) than in group C (2.2%), but the MZT rate following ICSI was not significantly different between the two groups. ZP thinning of D3 embryos may increase the risk of MZT in older women (≥38 years), but decrease it in younger women (≤37 years). ZP breaching may be useful to reduce the incidence of MZT in ICSI-generated blastocysts.

The aim of this study was to determine the pregnancy loss rate of amniocentesis with double-needle insertions in twin pregnancies. This was a retrospective study of twin pregnancies who underwent amniocentesis with double-needle insertion between 2010 and 2019 at a single center. The pregnancy loss rates were recorded as single or double fetal loss before 24 weeks’ gestation and within 4 weeks after the procedure. Risk factors for pregnancy loss after amniocentesis were also assessed. A total of 678 twin pregnancies with amniocentesis were finally included. The pregnancy loss rates before 24 weeks’ gestation and within 4 weeks after the procedure were 0.9% and 1.9%, respectively. Only one fetal loss was presumed to be a direct result of the procedure. All other cases were complicated by structural or chromosomal anomalies. Twin pregnancies with abnormal ultrasound findings had a significantly higher rate of pregnancy loss with a relative risk of 4.81 (95% CI [1.03, 22.2]). Our study showed a low pregnancy loss rate after amniocentesis in twin pregnancies with double-needle insertions technique of sampling, which can help decision making in prenatal screening and diagnosis for twin pregnancies.

Nature and nurture have always been a prerogative of evolutionary biologists. The environment’s role in shaping an organism’s phenotype has always intrigued us. Since the inception of humankind, twinning has existed with an unsettled parley on the contribution of nature (i.e. genetics) versus nurture (i.e. environment), which can influence the phenotypes. The study of twins measures the genetic contribution and that of the environmental influence for a particular trait, acting as a catalyst, fine-tuning the phenotypic trajectories. This is further evident because a number of human diseases show a spectrum of clinical manifestations with the same underlying molecular aberration. As of now, there is no definite way to conclude just from the genomic data the severity of a disease or even to predict who will get affected. This greatly justifies initiating a twin registry for a country as diverse and populated as India. There is an unmet need to set up a nationwide database to carefully curate the information on twins, serving as a valuable biorepository to study their overall susceptibility to disease. Establishing a twin registry is of paramount importance to harness the wealth of human information related to the biomedical, anthropological, cultural, social and economic significance.

The unique sources of artistic inspiration and talent of twin artists are examined. The professional literature is rich with twin studies of creativity, but lacking when it comes to specific artistic domains — for example, painting and sculpting. The section that follows provides reviews of current research on ethnic and racial factors affecting type of twin delivery, pregnancy outcomes when twins are conceived naturally or with reproductive assistance, the effects of intrauterine growth discordance on the timing of twin delivery, and three-dimensional (3D) assessment of twins’ facial resemblance. The final section summarizes information about twins in the media. The stories include twins distinguished for both baseball playing and physical injuries, twins who reached the National College Athletic Association’s Elite 8, a twin pair’s grave and epitaph, a mother who conceived twins three times in 2 years, twins in the Hockey Hall of Fame, and a set of superfetated twins.

The focus of this article is on insights gained from the extraordinary dynamics that took place between a pair of reunited monozygotic female twins from Greece. Topics include visualizing the co-twin prior to meeting, the unique love and attraction between the twins, a mother’s response to discovering her child’s cotwin and the challenges posed by insufficient kinship categories. The following section of this article surveys four recent twin research reports. They include Bereavement and Lifespan Associations; Novel Mutations in Twins; Parenting Premature Multiples; and Conjoined Twins. The final part of this article presents interesting and informative news about twins from popular sources. The topics covered are the passing of Madeline Albright (Secretary of State and mother of twins); identical twin songwriters; visually impaired twin and sibling skiiers; identical twin brothers who both received heart transplants; and the naming of the Genain quadruplets.

Selected highlights from the 2021 Congress of the International Society for Twin Studies are reviewed. The perspectives of a new graduate student member to the society are also included. Timely research covering issues related to maternal bonding with twins, twins with Peters anomaly, selective termination in dichorionic twin pairs and neuropsychological functioning in twins with neurofibromatosis is reviewed. The final part of this article includes interesting and informative media reports related to the world’s most premature survivor who is a twin, identical male baseball players, Malaysian twins switched at birth and a pair of the so-called ‘biracial’ twins.

Twin research proceeds at a rapid pace, with new findings constantly modifying our knowledge and thoughts about many issues. In the present article, this concept is applied to the writing of books and articles about twins, with special emphasis on the author’s recent experience. My lead essay in most contributions to the News, Views and Comment section of this journal is usually followed by a review of current research findings; however, significant events necessitated a departure from this format. At this time, it is important to both honor and remember colleagues and twins, both past and present. The final entry in this article highlights media events that variously pose biological and social implications for our field. They include the hardships of Ukrainian twins during wartime; twins born in different years; identical twin surrogacy, a quaternary family and abducted twins in Serbia.