Order of twins--random choice of natural selection?
Malewski, Z.; Seremak-Mrozikiewicz, A.; Drews, K.
Ginekologia Polska 74(3): 181-185
2003
ISSN/ISBN: 0017-0011 PMID: 12916254 Document Number: 565258
Testing of hypothesis that the order of twins is random. Confrontation of birthweight and incidence of stillbirth between twins. The group of 829 twin deliveries was investigated. Probability of distribution was assessed according to Bernoullie's trials schema. The first twin was usually heavier then the second one (p = 0.05), especially at term. Order of twin delivery was influenced by a birthweight difference > 250 g. In cases of single twin intrauterine death, the alive, term baby was delivered as the first one statistically more common (p = 0.029), despite of smaller number of cases. Discussion suggests that differences between twins are rather reasons of observed order than results. Hypothesis of natural selection of stronger baby for the first delivery was presented.