The association between maternal characteristics and different types and levels of discordance in triplet pregnancies.

Objective: This study evaluated the association of maternal factors known to influence outcomes of triplets, different discordance levels (-25, 25.1-35, and )35%), and three types (according to the birth weight of the middle-sized triplet) of birth weight discordance in triplets.

Methods: We used data collected by the Women's Health Division of Matria Healthcare, Inc. (Marietta, GA). We analyzed a cohort of 2706 triplet sets, to calculate the frequencies of different levels and types of birth weight discordance by maternal age, parity, weight, height, body mass index and weight gain at 24 weeks of gestation.

Results: We found a positive association between maternal parity and birth weight discordance level but no clear association between the other maternal factors and the level of discordance as well as the type of discordance. However, a trend was seen whereby overweight women had a trend towards the low-skew (a set comprising one large and two small triplets) type of birth weight discordance and an opposite trend in underweight women.

Conclusions: These results corroborate previous findings that nulliparity is associated with aberrant growth in triplet pregnancies.