Effect of fetal presentation on the amniotic fluid index.

Objective: The aim of this study was to determine whether the amniotic fluid index differs according to whether a fetus is in breech or cephalic presentation.

Study Design: Between January 1995 and April 1996 the amniotic fluid index was measured both immediately before and after attempted external cephalic version. Amniotic fluid indexes were measured by a senior obstetric resident or attending physician. Preprocedure amniotic fluid indexes and change in amniotic fluid index after successful and failed external cephalic version were compared with unpaired and paired Student t tests, respectively. P <.05 was considered statistically significant.

Results: Thirty consecutive women between 36 and 40 weeks' gestation with breech presentations were evaluated before undergoing an attempt at external cephalic version. The preprocedure amniotic fluid index was not different (P =.61) between women who had success (12.1 cm) and failure (11.4 cm) of attempts at external cephalic version. Successful external cephalic version was associated with a statistically significant increase (P <.0001) in amniotic fluid index with respect to gestations with a persistent breech presentation (3.14 vs -0.35).

Conclusion: Successful version from a breech to a cephalic presentation resulted in a significant increase in the amniotic fluid index. This should be considered when a breech presentation with a low normal amniotic fluid index is evaluated. Presentation of the fetus should be considered in evaluating amniotic fluid index distribution curves.