Pregnancy heartburn in Nigerians and Caucasians with theories about aetiology based on manometric recordings from the oesophagus and stomach.

A study by questionnaire of the incidence of pregnancy heartburn in two groups of Nigerians and one group of Caucasians showed an incidence of 9-8 per cent in all Nigerians as against 78-8 per cent in Caucasians. The difference was highly significant (chi 2 = 102-75; P less than 0-0001). An oesophageal manometric study of the lower esophageal sphincter in 12 non-pregnant women and in 12 pregnant Nigerians (10 without heartburn and 2 with heartburn) showed that the mean lower oesophageal sphincter pressure (+/- SD) in the pregnant patients without heartburn was 20-1 +/- 7-0 mm Hg as against 17-9 +/- 7-0 in the non-pregnant women. While one pregnant subject without heartburn had a lower oesophageal sphincter which was partially displaced into the thorax, none of the non-pregnant women had such sphincter displacement. The two pregnant women with heartburn had low resting sphincter pressures and in both of them the sphincters were partially in the thorax. It is argued that pregnancy heartburn is due to the displacement of the lower oesophageal sphincter into the negative pressure environment of the thorax where the sphincter is less capable of resisting reflux. It is also argued that pregnancy heartburn is commoner in Caucasians that in Nigerians because the spincter in non-pregnant Caucasians is often partly intrathoracic and is thus more easily displaced completely into the thorax by the pregnant uterus.