The introduction of assisted reproduction has resulted in an increase in the number of preterm multiple births. There is little information in recent medical literature on their outcomes in relation to birth sequence. Our aim is to describe the effect of birth order on hospital course in preterm (<37 wk) multiple births [triplets (A vs B vs C) and twins (A vs B)]. Data were collected for all consecutive multiple births between 1/1/90 to 11/30/96. There were 96 triplets (32 sets) and 342 twins (171 pairs). Statistical analyses were done to detect intragroup differences using chi square or student's t test. For triplets (TR) of all gestational ages (mean ± sem; GA 31.6 ± 0.3 wk; BW 1.54 ± 0.05 kg) the mortality was 1.9%. Among TR A, B and C, no difference was noted in prenatal steroids use, gender, Apgars, surfactant use, incidence of RDS, PDA, IVH, PVL, ROP, BPD, days on ventilator or CPAP and length of stay. Interestingly, a significantly higher number of C TR (3 A vs. 0 B vs. 8 C; p=0.005) were IUGR. For twins (TW) of all gestational ages (mean ± sem; GA 31.1 ± 0.2 wk; BW 1.59± 0.03 kg) the mortality was 5%. In this population no difference was seen among TW A vs. B in prenatal steroids use, gender, IUGR, Apgars, surfactant use, incidence of RDS, PDA, IVH, PVL, ROP, BPD, days on ventilator or CPAP and length of stay; however a significantly higher number of TW B (7 vs. 1; p=0.03) had NEC. Data for TW ≤30 wks (n = 108) were analyzed separately and significant outcomes are shown (*p<0.05, #p=0.01).Table

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For TW ≤30 wk, the increased incidence of IVH in TW A was not related to mode of delivery. Our findings of increased surfactant use and increased incidence of NEC in TW B were not related to lower Apgar scores and merit further study. We conclude that birth sequence has a significant impact on outcome in preterm multiple births.