The Tendency to Repeat Gestational Age and Birth Weight in Successive Births, Related to Perinatal Survival

Abstract. The risk of perinatal death was studied in relation to the tendency for mothers to carry their fetuses to similar gestational ages and birth weights in successive pregnancies. The data for this study are derived from all 635 140 births in Norway during a 10‐year period (1967‐76). The findings demonstrate that those babies that were born similar in age and size to their elder siblings ran the lowest risk of perinatal death. For example', the perinatal mortality rate (PMR) for second‐birth babies weighing between 2501 and 3000 g is 9.1 per 1 000 births if the first baby weighed 3000 grams or less. But the PMR is 50% higher, 13.3 per 1 000 births, when the first baby weighed between 3001 and 3 500 g. If the first baby weighed more than 3 500 g, then the PMR is 3 1/2 times greater, 32.1 per 1000 births.