Temperament differences between cotwins at least 15% discordant for birth-weight were compared for a group of 66 preterm twin pairs and a group of 70 fullterm twin pairs, assessed in the neonatal period. The assessment focused on irritability, resistance to soothing, activity, reactivity, and reinforcement value. For the most part, significant differences were not obtained between discordant preterm cotwins. Previous research [10] had demonstrated that the larger fullterm twin of discordant pairs was more irritable, more difficult to soothe, more active while awake and during sleep, less reactive to visual and auditory stimuli, and less reinforcing to the examiner than the smaller cotwin. It was concluded that, for the behavioral variables measured, the fullterm group is at higher risk than the preterm group, and that both the lighter and the heavier discordant twins displayed signs of early behavioral risk. The findings suggested that the continued gestation for cotwins discordant in weight may be a risk period for early temperament development of the twins.

A randomized controlled trial of periconceptional multivitamin supplementation (including 0.8 mg folic acid – see the Materials and Methods section for the precise composition of the multivitamin and trace-element supplementation) was carried out for at least 28 days before conception. The trial was continued until at least until the second missed menstrual period to test the effectiveness of this new primary preventive method in the reduction of neural tube defects. However, other pregnancy outcomes were also evaluated. Of a total of 5,502 pregnant women, 4,846 births were analysed in the final data base. The rate of multiple births was significantly higher in the multivitamin group (3.8%) than in the placebo-like trace-element control group (2.7%), and in both groups exceeded the multiple birth rate of 2.2% in the Hungarian population at large. 7.3% of women in the multivitamin and 7.9% of women in the trace-element groups had received ovarian stimulation treatment (mainly clomiphene) for hormonal dysfunctions, eg. anovulation. Nonetheless, our study showed that periconceptional multivitamin supplementation, with or without ovarian stimulation, increases the rate of multiple births.

Amniotic fluid elastolytic activity was assessed in a group of 120 women who delivered preterm infants and in 35 women who delivered at term. Amniotic fluid elastolytic activity decreases as pregnancy progresses. The lecithin-to-sphingomyelin (L/S) ratio in women's amniotic fluid was determined by the method developed by Gluck and associates [6] and elastolytic activity by that developed by Mehdi and associates. A significant negative correlation was found between the amniotic fluid L/S ratio and amniotic fluid elastolytic activity (r = −0.932; p<0.001).

The border value of elastolytic activity that indicates lung maturity (L/S ratio equal to or greater than 2) is 2.01 ± 0.05 mmol/min ml. In the amniotic elastolytic activity test, it is the value that differentiates mature from immature lungs. The amniotic fluid elastolytic activity test is characterized by high sensitivity (91.43%) and specificity (91.67%), high positive prognostic value (76.19%) and low negative prognostic value (2.65%). The test parameters do not therefore differ greatly from those of the Gluck test. Moreover, the amniotic fluid elastolytic activity test is cheaper and takes less time to perform.

Cette étude nous a permis de mettre à jour les différents modes d'intéractions qu'une mère établit avec ses jumeaux, ainsi que les évolutions possibles qui en résultent. Mais, bien plus, nous avons modélisé la façon dont les jumeaux élaborent leurs structures de l'activité de connaissance en fonction des sollicitations du milieu, ainsi que l'interdépendance qui les caractérisent.

Grâce à des examens opératoires, réalisés sur une population de 14 couples âgés de 6 a 10 ans, nous avons mis à jour un décalage intra-couple au niveau de la genèse de ces mêmes structures de l'activité de connaissance. Nous nous sommes apercus que sur le plan de la genèse de l'organisation cognitive l'un des enfants a développé des structures figuratives, et l'autre des structures opératives lui permettant d'avoir une connaissance de la réalité plus étendue.

Les liens de dépendance, de fusion, unissant les jumeaux entre eux, pourraient être dus à un développement cognitif parasitaire. Ils génèrent un lien gémellaire à partir de défaillances structurales qui vont apparaître chez chacun d'eux, ce qui ne permet aucunement leur autonomisation réciproque.

Puisque des déficiences apparaissent dans les structures de l'activité de connaissance de ces enfants, les problèmes qu'ils recontrent pourraient trouver leur solution dans une remédiation cognitive opératoire.

The 20 reported cases of MZ female twins discordant for X-linked diseases are reviewed. In such twins the X-inactivation pattern is opposite skewing (abnormal allele inactivated in most cells of the normal twin, and normal allele inactivated in most cells of the affected twin) or skewing in one twin and random in the cotwin. The diseases involved map in two specific regions: Xq27-28 and Xp21. The only exceptions are Fabry's disease and Aicardi's syndrome, which map in Xq22 and Xp22 respectively. No concordant MZ female carrier twins, either normal or affected, have been described. Three main hypotheses have been proposed to explain such characteristics [2, 5, 14], but none is completely satisfactory. The constant discordance for X-linked diseases in MZ female twins has important consequences for genetic counselling.