The significance of the time interval in twin delivery.

In order to evaluate the influence of the time interval on the second twin in twin deliveries, we have used more precise criteria than have been used in the literature to date. In the period from July 1, 1970 to December 31, 1974, 35 twin deliveries in our hospital were analyzed, in which both twins fulfilled the following criteria: 1. vertex presentation 2. vaginal deliveries 3. birth weight above 2000 g. We analyzed various parameters in the clinical and acidity score of the second twin alone as well as in comparison to the first twin. The following points of view were considered: 1. The more sensitive aspect of morbidity was utilized by including the assessment of the state of the newborn rather than just mortality. 2. Since Caesarean sections in twins are often performed for a fetal indication, short time intervals between the birth of both infants correlate intrinsically with a higher risk for the second twin. Therefore we considered only vaginal deliveries in order to exclude this intrinsic correlation. 3. By excluding infants below a birth weight of 2000 g, the influence of the low birth weight of the second twin was eliminated. 4. The frequently occurring positional anomalies of the second twin will deteriorate the conditions independent of the time interval. therefore we have considered only births from vertex presentations. A comparison of the acidity state demonstrated that the actual pH values in the umbilical artery blood of these second twins (Fig. 1) decrease statistically significantly with increasing time intervals. this is also true for metabolic acidity (pHqu40). The differences of the actual pH values (Fig. 2) and the pHqu40 values between the first and second twin decreases significantly also with an increasing time interval. Our results indicate that obstetricians, according to the clinical conditions, should accomplish the birth of the second twin as soon as possible after the birth of the first twin.