A randomised trial of progesterone prophylaxis after midtrimester amniocentesis.

Background: Midtrimester amniocentesis to investigate fetal karyotype carries a small risk of fetal loss.

Aim: To test the hypothesis that progesterone prophylaxis may reduce this.

Study Design: A randomised controlled trial comparing a short prophylactic treatment with progesterone after amniocentesis with untreated controls.