preterm labour or other obstetric complications in patients with anxiety and ... Jacksonville,. FL 32214-5227, USA ... Department of Obstetrics and Gynaecology,.
LETTERS
Psychological distress and preterm delivery Consider urogenital infection EDITOR,-Morten Hedegaard and colleagues' study on psychological distress in pregnancy and preterm delivery depended on questionnaires completed by patients.' Answers to questions about urogenital infections in pregnancy are unreliable since many urogenital infections are asymptomatic, as we have shown.' We found a significantly higher prevalence of appreciable bacteriuria and pathogenic bacteria in the genital tract of patients with preterm labour. It has been suggested that microorganisms may trigger preterm labour by synthesising prostaglandins. Almost half of women admitted in spontaneous early preterm labour have abnormal genital colonisation compared with only 15% in control groups.3 Might some of the patients with preterm labour in Hedegaard and colleagues' study have had urogenital colonisation without local symptoms, which made them unwell, anxious, and depressed? Hedegaard and colleagues suggest that stress causes preterm labour through the release of oxytocin, but the likelihood of a physiological role for oxytocin in the initiation of spontaneous labour at term or earlier has been largely rejected. There is no evidence that oxytocin will induce the formation of gap junctions between myometrial cells. The central role of prostaglandins in labour, however, is well documented. Perkin et al did not find an increased incidence of preterm labour or other obstetric complications in patients with anxiety and depression.4 Nor did we find an increased incidence of preterm labour in our depressed patients, who included four patients with known depression or malignancy, or who had suffered a death in the family. Instead we found anxiety and depression to be more common in women who did not go into labour spontaneously until 42 weeks.5 All possible causes of preterm labour should be excluded by detailed investigation, particularly for urogenital colonisation, before psychological distress is given as the cause and elaborate mechanisms to reduce stress are introduced. Postal questionnaires cannot identify the causes of preterm labour in asymptomatic women. Their use is a possible source of bias in the study and may explain the discrepancy between the findings of two recent studies.' 4 J B SHARMA M R B NEWMAN R JSMITH Kettering and District General Hospital,
Kettering, Northamptonshire NN16 8UZ I Hedegaard M, Henriksen TB, Sabroe S. Secher NJ. Psychological distress in pregnancy and preterm delivery. BMJ
2 Sharma JB. Prevalence of pathogenic bacteria in genital tract in preterm labour. J7ournal of Obstetrics and Gnoaecolog of India 1990;40:229-34. 3 Lamont RF, Fisk N. The role of infection in the pathogenesis of preterm labour. In: Studd J, ed. Progress in obstetrics and gynaecology. Vol 10. London: Churchill iUvingstone, 1993: 135-58. 4 Perkin MR, Bland JM, Peacock JL, Anderson HR The effect of anxiety and depression during pregnancy on obstetric complications. BrJ Obster Gynaecol 1993;100:629-34. 5 Sharma JB, Smith RJ, Wilkin DIW. Induction of labour at term. BMJ 1993;306:1413.
Unconvincing link EDITOR,-Morten Hedegaard and colleagues' article on psychological distress in pregnancy and preterm delivery highlights an important issue.' We found it odd, however, that the authors decided to collapse the continuous questionnaire scores (which are apparently interval data) into an ordinal trichotomy. We also found it odd that this resulted in a more significant result. The reported relative risk of preterm delivery on the basis of interval data was 1-022 (95% confidence interval 1-007 to 1-036), but this figure rose to 1 75 (1 20 to 2 54) when ordinal data were used. The more powerful interval data might be expected to yield a more significant difference if such a difference actually existed. On what basis were the questionnaire scores divided into low, moderate, and high? Hedegaard and colleagues say only that the score of 24 was chosen to differentiate low from moderate scores as "this included scores above the mean" and the cut off point of 31 "divided the scores above the mean into a smaller 'high' and a larger 'moderate' group." Although the study showed a significant difference in the relative risk of preterm labour with increasing psychological stress, this difference does not seem to be clinically important. A relative risk of 1 022 implies at most a small skewing of the odds. We tried to calculate the population attributable risk to show what part psychological stress played in the overall risk of preterm delivery but were unable to do so from the data given. Providers of health care should think about p'sychological stress in all patients, especially those facing a major life event such as pregnancy, but we remain unconvinced that it is a clinically important factor in preterm delivery. REBECCA S KING W R KISER
Department of Family Practice, Naval Hospital, 2080 Child Street,
934
MORTEN HEDEGAARD TINE BRINK HENRIKSEN NIELS JORGEN SECHER
Jacksonville, FL 32214-5227, USA
1 Hedegaard M, Henriksen TB, Sabroe S, Secher NJ. Psychological distress in pregnancy and preterm delivery. BMJ3
1993;307:234-9. (24 July.)
Perinatal Epidemiological Research Unit, Department of Obstetrics and Gynaecology, Aarhus University Hospital, DK-8000 Aarhus C,
Denmark SVEND SABROE
Institute of Epidemiology and Social Medicine, Aarhus University,
1993;307:234-9. (24 July.)
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and psychological distress. As psychological distress has been associated with raised serum corticosteroid concentrations,' which suppress immunological resistance, we would expect psychological distress to lead to asymptomatic microbiological changes in the urogenital tract rather than the other way round. Brooke et al did not find any association between psychological distress and birth weight for gestational age,2 but their study did not consider gestational age and is therefore not comparable with ours. Perkin et al found an association between depression and preterm delivery (odds ratio of 1-28 per step, four steps), although it was not significant (pO- 10).' According to Perkin et al, women in the highest quartile had a risk estimate of 2 10 (1 283) compared with women in the lowest quartile.' Sharma and colleagues give examples of term deliveries in four depressed patients and two patients who experienced stressful life events during pregnancy. The examples do not contradict our findings: our study was population based, and the risks were based on frequencies. Even in the high risk group 94-6% delivered at term (table III). Rebecca S King and W R Kiser found that it was impossible to review the scores obtained with the general health questionnaire for the 197 women who delivered before term. In table III, however, the mean and SD of the scores for the women who did and did not deliver before term are presented separately. Furthermore, King and Kiser ask why we collapsed an interval scale into a trichotomy. To give the most information we presented both results. An odds ratio of 1-022 (95% confidence interval 1-007 to 1 036, p
