Influence of clinical variables on triplet birth weight

The small size of most reported triplet series has resulted in conflicting statements about the influence of several clinical variables on triplet birth weight. Therefore, obstetrical and neonatal data were collected on 196 mothers and their 580 infants (8 stillbirths excluded). Gestational age was based on the date of fertilization in 13 IVF triplets and on the date of ovulation in 90 medically induced triplets. Obstetrical and ultrasonic criteria were used to estimate the date of confinement in 93 spontaneous triplets. Birth weight appeared to be higher in males and with higher maternal parity, independent of gestational age. The apparent effect of medical technologies such as ovulation induction or IVF on combined triplet birth weight disappeared when maternal parity and fetal gender were controlled. Preeclampsia, maternal race and zygosity were not significantly associated with birth weight. While birth order did not significantly effect ultimate birth weight, the heaviest triplet did present first more often than would be expected by chance alone. Future evaluation of neonatal outcome data in multifetal gestations should control for gestational age, fetal gender and maternal parity. It appears that triplet birth weight is not affected by etiology, which is important given the significant impact of medical technologies.