PREGNANCY ORDER - A FACTOR INFLUENCING BIRTH-WEIGHT IN TWIN GESTATIONS

To test the hypothesis that increased twin birth weight is expected wi th increased parity, we conducted a retrospective, cross-sectional eva luation of 430 twins, focusing on birth weight and growth discordance parameters in five parity groups (para 1-4 and greater than or equal t o 5). The mean birth weight of twin A, B and both twins was significan tly lower in primiparous patients as compared to para 2-4 but not as c ompared to para greater than or equal to 5 patients. The frequency of twins weighing <1,500 g was similar in all groups, but a significantly higher frequency of twins weighing 1,500-2,500 g and lower frequency at > 2,500-g twins were found in the para 1 group as compared to the g roups with higher parities. Presentation combinations were not differe nt in the five parity groups, nor were the frequencies of growth disco rdance categories. However, discordants among pairs, with each infant weighing <2,500 g, occurred almost twice as often in para greater than or equal to 5 as compared to the other parity groups. Our data indica te that primiparae parae seem to have significantly smaller twins as c ompared to multiparae. This trend was independent of the presentation combinations and growth discordance pattern and seems to result from a higher frequency of twins weighing 1,500-2,500 g in primiparae.