Lower oesophageal sphincter pressure during early pregnancy: manometric studies before and after abortion.

Resting lower oesophageal sphincter pressure (L.O.S.P.) was determined in 14 pregnant women with heartburn and 12 pregnant women without heartburn before (10 to 18 weeks of gestation) and in the first week after an elective abortion. Mean L.O.S.P. in pregnant women with heartburn was 11.5 ± 1.5 mm Hg before and 17.3 ± 1.8 mm Hg after abortion, the difference being statistically significant (p < 0.001). In the group of pregnant women without heartburn the mean resting L.O.S.P. before and after abortion was not significantly different. Although the exact mechanism by which gastro-oesophageal reflux occurs during early pregnancy is not entirely understood, it appears that hormonal changes (elevated serum concentrations of progesterone and oestrogens) play a major role by depressing L.O.S., the main antireflux barrier.