The amniotic fluid index in normal twin pregnancies

OBJECTIVE: We sought to investigate the amniotic fluid index for individual gestational sacs of twin pregnancies. STUDY DESIGN: Four hundred eighty-eight patients with normal diamniotic twi ns were examined between 14 and 40 weeks' gestation. The dividing membrane between twin fetuses was identified. An amniotic fluid index was then obtai ned for each gestational sac. RESULTS: The median amniotic fluid index in individual twin gestational sac s rises slowly from 14 to 16 weeks' gestation to 23 to 28 weeks' gestation and then gradually declines. The median amniotic fluid index values by gest ational age for twin A and twin B are not statistically different. Although twin pregnancies have a slightly lower median amniotic fluid index value t han singleton pregnancies, the difference is also not statistically signifi cant. CONCLUSION: individual amniotic fluid indices can be obtained in twin pregn ancies, and the values are comparable with those of singleton gestations.