We report a very rare case of monochorionic dizygotic twins conceived spontaneously. The fetuses were sex-discordant in ultrasonography despite being monochorionic twins. After birth, the girl and boy showed normal phenotypes but they showed blood chimerism in karyotype and blood group type.

We evaluated the outcomes and adverse events after fetoscopic laser surgery (FLS) for twin–twin transfusion syndrome (TTTS) using the Solomon technique in comparison to the selective technique. A retrospective analysis of a single-center consecutive cohort of FLS-treated TTTS using the selective (January 2010 to July 2014) and Solomon (August 2014 to December 2017) techniques was performed. Among 395 cases, 227 underwent selective coagulation and 168 underwent the Solomon technique. The incidence rates of recurrent TTTS (Solomon vs. selective: 0% vs. .9%, p = .510) and twin anemia–polycythemia sequence (.6% vs. .4%, p = .670) were very low in both groups. The incidence rates of placental abruption (Solomon vs. selective: 10.7% vs. 3.5%, p = .007) and preterm premature rupture of the membranes (pPROM) with subsequent delivery before 32 weeks (20.2% vs. 7.1%, p < .001) were higher in the Solomon group. The median birth recipient weight was significantly smaller in the Solomon group (1790 g vs. 1933 g, p = .049). The rate of survival of at least one twin was significantly higher in the Solomon group (98.2% vs. 93.8%, p = .046). The Solomon technique and total laser energy were significant risk factors for pPROM (odds ratio: 2.64, 1.07, 95% CI [1.32, 5.28], [1.01, 1.13], p = .006, p = .014, respectively). These findings suggest that the Solomon technique led to superior survival outcomes but increased risks of placental abruption, pPROM and fetal growth impairment. Total laser energy was associated with the occurrence of pPROM. Close attention to adverse events is required for perinatal management after FLS to treat TTTS using the Solomon technique.

Selective termination is the term used for the elimination of an abnormal fetus. In contrast, multifetal pregnancy reduction refers to the termination of one or more members of a twin or higher-order multiple birth set, respectively, to reduce the high risks associated with these pregnancies. The procedure can also be used when a serious physical condition is detected prenatally in a member of a multiple birth set. In a minority of cases, selective termination has reduced two healthy fetuses to one when parents wanted just one additional child in the family. In the present article, the perspectives of a surviving twin whose family wished to terminate both healthy fetuses are examined. Next, past and present twin studies of primordial dwarfism, public service motivation, an analytical model, the global twinning rate and germline differences are summarized. The article concludes with a synopsis of twin-related news that covers twins and Dyngus Day, triplets born in an Austrian displaced persons’ camp, the film Superior — about estranged identical twin sisters, a couple adopting their own twins after surrogacy and a new case of twins and primordial dwarfism, a condition introduced in the research reviews.

Every reared-apart monozygotic (MZ) twin pair offers a fresh perspective on human developmental questions. This is true regardless of whether the co-twins were raised in the same country or across the globe. The members of two pairs of separated MZ female twins have recently come to attention. In one case the twins were raised by different families in Argentina; in the other case the twins were raised by different families in Sweden and Vietnam. The perceptions and perspectives of these twins are insightful. The twin research section that follows begins with a tribute to our late esteemed colleague, Dr Isaac Blickstein (1953−2020). Research concerning the infanticide and sacrifice of Archaic-aged twins and triplets and prehistoric twin burials is reviewed next. Highlights from a conference focused on the 2018 film Three Identical Strangers are also included in this portion. The final section of this article includes media reports of an atypical twin father, an actor’s twin brother, a twin link to the 1921 Tulsa, Oklahoma massacre, the birth of superfetated twins, twin comedians and script writers and Indian twins’ tragic loss to COVID-19.

Craniosynostosis involves the early closure of one or more joints connecting the bones of an infant’s skull. A case of young monozygotic (MZ) male twins with an unidentified variant of this condition is described, followed by a summary of relevant published reports. This overview is followed by descriptions of a kangaroo care program for premature twins, developmental delay in an MZ twin pair, osteosarcoma in one MZ twin and controversial issues in the management of multiple pregnancies. Media reports of twin and triplet Olympic athletes, a twin’s rescue from a crocodile, the birth of twin pandas in Japan, a case of twin surrogacy and the birth of identical triplets are also presented.

Research into the origins of twinning has focused mostly on contributions from the female side of the family. A review of current findings suggests that possible male contributions to twinning events have been overlooked. This section is followed by brief reviews of twin research concerning monozygotic twins discordant for Parkinson’s disease, fetal loss in twin pregnancies following prenatal diagnosis, uterine rupture and repair in an early twin pregnancy and a twin study of affectionate communication. The concluding portion of this article presents human interest stories involving twins that are both informative and poignant, namely conjoined twins in a triplet set, identical twin nurses who delivered identical twins, identical twins discordant for COVID-19 recovery course, identical twins who passed away from COVID-19 and archeological finds of the oldest identical twins.

Modern reproductive technology and revisions of conventional family structures have yielded a curious array of twin-like sibships. Many of these pairings pose the same rearing questions and educational issues for parents and teachers as do ordinary monozygotic and dizygotic twins. This article considers how we classify these sibships, given the important implications for the pair members, their families, their friends and the professionals who care for them. Next, reviews of research on twins’ birth weight and brain development, twinning and vocabulary knowledge, fetal loss in twin pregnancy and twin-family Olympic medal winners are presented. The final topic covers recent media attention to young twin soldiers, a twin-run laundry, a male-female pair’s political differences, a twin-based graphic novel and twin sisters’ deliveries.