Incidence and birth weight characteristics of twins born to mothers aged 40 years or more compared with 35-39 years old mothers: a population study

Objective: To compare the incidence of twin births and their birth weight characteristics in mothers aged greater than or equal to 40 years with those of mothers aged 35-39 years. Methods: We used a population-based cohort of Israeli twins delivered between 1993-98 to compare birth weight characteristics of 510 and 2102 twin pairs delivered to mothers aged greater than or equal to 40 years (cases) and 35-39 years (controls), respectively. Results: The incidence of twin mothers aged 40 years or more increased 50% during the study period, ten times more than mothers aged 35-39. There were significantly more nulliparas (P < .001, OR 1.54, 95% CI 1.2, 1.9) and more para <greater than or equal to>4 (P < .004, OR 1.38, 95% CI 1.1, 1.7) among older mothers. Irrespective of parity, then were no significant differences between mean twin birth weight, total twin birth weight <3000 g, 3000-4999 g, and greater than or equal to 5000 g, and frequencies of very low birth weight neonates. Conclusions: Twin birth at the age of greater than or equal to 40 years is significantly more likely among either nulliparas or para greater than or equal to4. Birth weight characteristics of twins delivered to mothers aged greater than or equal to 40 years are not different from those delivered to 35-39 years old mothers.