Trends in triplet stillbirth rates in Japan, 1975-1998.

Stillbirth rates of triplet births in the whole of Japan were analyzed using vital statistics from 1975 to 1998. Stillbirths were registered at 12 weeks gestation or later. The stillbirth rate was significantly higher in like- than in unlike-sex triplets for 1975-1998. During the 23-year period the stillbirth rate decreased from 342 to 49 per 1000 total births for like-sex and from 195 to 54 for unlike-sex triplets. The decrease in the stillbirth rate in the 23- year period was greater in both like- and unlike-sex triplets than in singleton and twin births. Risk factors for stillbirth in triplets were like-sex, youngest or oldest maternal age groups, shorter gestational age and lower birthweight. It is recommended that the optimum period to give birth for triplet pregnancies is 34-35 weeks of gestation for Japanese women.