Epidemiological and clinical analysis of a consecutive series of conjoined twins in Spain.

PURPOSE: The aim of the study was to analyze the frequency and certain epidemiological characteristics of a consecutive series of conjoined twins born in Spain. MATERIAL AND METHODS: We used data from the Spanish Collaborative Study of Congenital Malformations for the period April 1976 to 2006. Because the Spanish law permitting voluntary termination of pregnancies (TOP) when the fetus presented malformations was effective by the end of 1985, we analyzed the data in 4 periods, 2 before 1986 and 2 after. During the first period (1976-1979) only live births were recorded, whereas both still and live births were included in the other three (1980-1985, 1986-1995, and 1996-2006). In the present study, the cases were classified as symmetrical (16 pairs) and asymmetrical (1 pair) conjoined twins. Each pair of conjoined twins was considered as only one case for calculations, regardless of the type of union. RESULTS: Among a total of 2,281,604 consecutive births between 1980 and 2006, there were a total of 15 cases of symmetrical conjoined twins giving a frequency of 0.70 per 100,000 (1/152,107), whereas there was only 1 stillborn asymmetrical conjoined twin pair (0.04/100,000). Among the 13,418 consecutive stillborns surveyed, 6 cases of conjoined twins were identified (either symmetrical or asymmetrical) giving a frequency of 44.72 per 100,000, and 11 pairs were identified among the 2,425,583 total live births surveyed during the first period 1976 to 1979, a frequency of 0.45 per 100,000. Thus, the frequency among stillborn infants is 99.34 times higher than that observed among live births. However, the frequency for the total births (3 last periods) showed a decreasing trend from 1.47 per 100,000 birth in the first period (1980-1985) when TOP was illegal, to a value of 0.09 per 100,000 in the last period, more than 16-fold lower, probably because of the TOP of affected fetuses. Therefore, we consider that the frequencies observed in the period 1980 to 1985 are the basal values in our population. The most frequent type observed was thoracopagus, with an overall prevalence at birth of 0.44 per 100,000 (1/228,160) from 1980 to 2006, representing 58.82% of the total population of symmetric conjoined twin pairs. Diprosopus pairs were the next most common group (11.76%). Most of the cases were females (4 males/11 females), and although this appeared to be mainly because of the thoracopagus pairs (males-females, 2:8), in such a small number of cases, it is not possible to determine the ratios for the other groups. Gestational age was significantly shorter than in control twins for each type studied. CONCLUSIONS: We conclude that it is incorrect to consider that all types of conjoined twins have the same epidemiological characteristics, such as the frequency at birth. The differences observed may be related with the distinct embryo-fetal mortality of each type of conjoined twins in different populations, and the sex ratio, among others.

A neonatal form of Steinert's myotonic dystrophy in twins after in vitro fertilization.

OBJECTIVE: To report a case of nonidentical twins affected with a congenital form of Steinert's myotonic dystrophy (DM1), conceived by IVF owing to parental sterility, in which the mother presented a paucisymptomatic form of DM1 which was diagnosed as a result of the condition inherited by the twins. DESIGN: Case report. SETTING: Neonatal intensive care unit of a tertiary hospital. PATIENT(S): Newborn twins affected with the congenital form of DM1 and a 35-year-old nulliparous mother. INTERVENTION(S): In vitro fertilization. MAIN OUTCOME MEASURE(S): Molecular study of the CTG triplet expansion related with DM1. RESULT(S): Molecular study evidenced a pathologic expansion in both twins as well as in their mother. CONCLUSION(S): This case should serve as a reminder to practitioners that assisted reproductive techniques have opened the possibility that asymptomatic or paucisymptomatic carriers of a genetic syndrome can inadvertently conceive fetuses affected with more serious forms of the illness.

Pure partial trisomy 7q: two new patients and review.

We report on two new cases with a pure partial trisomy of the long arm of chromosome 7. Patient 1 was a female who showed cleft palate with retrognathia, cardiomyopathy, and pulmonary hypertension. Patient 2 was a male who showed microretrognathia, cleft palate, micropenis, camptodactyly, and clynodactyly. High-resolution G-bands (550-850) karyotype showed that patient 1 had an extra chromosome, which resulted from the adjacent 3:1 segregation from a maternal balanced reciprocal translocation, and patient 2 had an abnormaly Y chromosome. Fluorescent in Situ Hybridization (FISH) analysis with a whole chromosome painting confirmed in the first patient that the extra chromosome was from chromosome 7, and in patient 2 the abnormal Y chromosome had extra material of chromosome 7 origin. Three different clinical entities have been described as the product of the partial trisomy of three different 7q regions, although some authors have found no karyotype-phenotype correlations. Of the patients presented here, patient 1 had trisomy of those three regions, and patient 2 had trisomy of two of those regions.