- Email: [email protected]
Risk factors for preterm delivery
CORRESPONDENCE
Nowadays, about half the total population (57 million) of Bangladesh is known to drink toxic concentrations of arsenic.3 9 years have already passed since its first detection, but only 10 000 patients have been confirmed as having chronic arsenic poisoning. Some natural protection might therefore remain to be explored. Bae and colleagues suggest that the 10–35% higher amount of arsenic in cooked rice than raw rice might be due to chelation by rice. We are, at present, examining the effect of rice bran on the extent of arsenic absorption from the gastrointestinal tract. Bran might have some chelating property so that arsenic within the gastrointestinal tract will not be absorbed and pass through with the faeces. Mir Misbahuddin Department of Pharmacology, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh (e-mail: [email protected]) 1
2
3
Bae M, Watanabe C, Inaoka T, et al. Arsenic in cooked rice in Bangladesh. Lancet 2002; 360: 1839–40. Sinha SK, Misbahuddin M, Ahmed ANN. Factor(s) involved in the development of chronic arsenic poisoning. Arch Environ Health (in press). Mudur G. Half of Bangladesh population at risk of arsenic poisoning. BMJ 2000; 320: 822.
Risk factors for preterm delivery Sir—To the list of possible risk factors for preterm delivery suggested by Michael Slattery and John Morrison (Nov 9, p 1489),1 we would like to add heavy liquorice consumption, which we have investigated in two series of mothers in Finland.2,3 We calculated the maternal intake of glycyrrhizin—a constituent of liquorice—using food tables, and showed that heavy intake (⭓500 mg/week) during pregnancy was associated with increased risk of preterm birth (odds ratio 2·15 [95% CI 0·93–4·95] for birth at <37 weeks of gestation, and 3·07 [1·17–8·05] for birth at <34 weeks).3 Odds ratios were adjusted for mother’s age, parity, smoking, and sex of the child. The finding might have clinical relevance only in countries such as Denmark, Finland, the Netherlands, and northern Germany where consumption of liquorice-type sweets is popular. According to our data, 10% of mothers in Helsinki are heavy consumers.2 However, because glycyrrhizin might act through cortisol-related or prostaglandin-
436
related pathways, it could possibly be used in the investigation of mechanisms causing preterm delivery. *Timo E Strandberg, Sture Andersson, Anna-Liisa Järvenpää *Department of Medicine (TES), and Department of Paediatrics (SA, A-LJ), University of Helsinki, PO Box 340, 00029 Helsinki, Finland (e-mail: [email protected]) 1 2
3
Slattery MM, Morrison JJ. Preterm delivery. Lancet 2002; 360: 1489–97. Strandberg TE, Järvenpää A-L, Vanhanen H, McKeigue PM. Birth outcome in relation to licorice consumption during pregnancy. Am J Epidemiol 2001; 153: 1085–88. Strandberg TE, Andersson Sture, Järvenpää A-L, McKeigue PM. Preterm birth and licorice consumption during pregnancy. Am J Epidemiol 2002; 156: 803–05.
Sir—In their review of the various epidemiological risk factors for preterm delivery,1 Michael Slattery and John Morrison are surprisingly discreet about dietary habits. They mention only that possible explanations for social disadvantage include worse nutritional status. Since their paper is followed by six references dated 2002, a report of the prospective cohort study by Olsen and Secher might have been included.2 Today one can claim that low consumption of seafood is the bestknown risk factor for preterm delivery. Danish pregnant women (n=8729) were interviewed about their dietary habits. The occurrence of preterm delivery differed significantly across four groups of seafood intake. Adjusted odds for preterm delivery were increased by a factor of 3·6 (95% CI 1·2–11·2) in the zero consumption group compared with the highest consumption group. Of course, Olsen and Secher assessed dietary habits that preceded to a great extent the beginning of pregnancy. This is how we explain the apparent contradiction between the Danish results and the results of our own studies: encouraging pregnant women to increase their consumption of sea fish had no effect on the duration of pregnancy.3,4 Dietary recommendations in antenatal clinics probably occur too late to have detectable effects in the perinatal period.
3
4
Odent MR, McMillan L, Kimmel T. Prenatal care and sea fish. Eur J Obstet Gynecol Reprod Biol 1996; 68: 49–51. Odent M, Colson S, De Reu P. Consumption of sea food and preterm delivery: encouraging pregnant women to eat fish did not show effect. BMJ 2002; 324: 1279.
Authors’ reply Sir—In general terms, we believe that sound conclusions about the role of nutritional factors in preterm birth are difficult to draw.1,2 We are aware of the previously published data by Timo Strandberg and colleagues3 regarding liquorice consumption during pregnancy. That study involved 95 mothers delivered preterm for any reason except twins, elective caesarean section, and induced delivery. Close scrutiny of these data indicate that further assessment of the role of liquorice in preterm birth might be appropriate before routinely advising women. First, the cases included represent a heterogeneous group of preterm births; second, the data were collected on three maternity wards by use of retrospective postnatal questionnaires—ie, many months later; and third, on statistical analysis, there was no significant difference between mothers of cases (ie, preterm birth) and mothers of controls (term birth) in terms of heavy glycyrrhizin intake (p<0·06). Michel Odent raises an interesting point in that reduced rates of preterm delivery and low birthweight have been seen in fish-eating northern European populations.4 Whether this effect (ie, significant prolongation of gestation) can be mimicked by women increasing their consumption of sea fish, and if so at a particular period of gestation, remains to be seen. Abnormal or insufficient fatty acid nutrition might have a role in adversely affecting prostaglandin and other eicosanoid metabolism. Various studies are underway to examine these issues and the potential perinatal benefits that might arise from supplementation with long-chain n-3 fatty acids.4,5 Michael M Slattery, *John J Morrison
Primal Health Research Centre, 72 Savernake Road, London NW3 2JR, UK (e-mail: [email protected])
Department of Obstetrics and Gynaecology, National University of Ireland, Galway, Republic of Ireland (MMS); and *Clinical Science Institute, University College Hospital, Newcastle Road, Galway (JJM) (e-mail: [email protected])
1
1
Michel Odent
2
Slattery MM, Morrison JJ. Preterm delivery. Lancet 2002; 360: 1489–97. Olsen S, Secher NJ. Low consumption of seafood in early pregnancy as a risk factor for preterm delivery: prospective cohort study. BMJ 2002; 324: 447.
2
Kramer MS. Nutritional advice in pregnancy (Cochrane Review). In: The Cochrane Library, issue 4. Oxford: Update Software, 2002. Cohen GR, Curet LB, Levine RJ, et al. Ethnicity, nutrition, and birth outcomes in
THE LANCET • Vol 361 • February 1, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet Publishing Group.
Nowadays, about half the total population (57 million) of Bangladesh is known to drink toxic concentrations of arsenic.3 9 years have already passed since its first detection, but only 10 000 patients have been confirmed as having chronic arsenic poisoning. Some natural protection might therefore remain to be explored. Bae and colleagues suggest that the 10–35% higher amount of arsenic in cooked rice than raw rice might be due to chelation by rice. We are, at present, examining the effect of rice bran on the extent of arsenic absorption from the gastrointestinal tract. Bran might have some chelating property so that arsenic within the gastrointestinal tract will not be absorbed and pass through with the faeces. Mir Misbahuddin Department of Pharmacology, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh (e-mail: [email protected]) 1
2
3
Bae M, Watanabe C, Inaoka T, et al. Arsenic in cooked rice in Bangladesh. Lancet 2002; 360: 1839–40. Sinha SK, Misbahuddin M, Ahmed ANN. Factor(s) involved in the development of chronic arsenic poisoning. Arch Environ Health (in press). Mudur G. Half of Bangladesh population at risk of arsenic poisoning. BMJ 2000; 320: 822.
Risk factors for preterm delivery Sir—To the list of possible risk factors for preterm delivery suggested by Michael Slattery and John Morrison (Nov 9, p 1489),1 we would like to add heavy liquorice consumption, which we have investigated in two series of mothers in Finland.2,3 We calculated the maternal intake of glycyrrhizin—a constituent of liquorice—using food tables, and showed that heavy intake (⭓500 mg/week) during pregnancy was associated with increased risk of preterm birth (odds ratio 2·15 [95% CI 0·93–4·95] for birth at <37 weeks of gestation, and 3·07 [1·17–8·05] for birth at <34 weeks).3 Odds ratios were adjusted for mother’s age, parity, smoking, and sex of the child. The finding might have clinical relevance only in countries such as Denmark, Finland, the Netherlands, and northern Germany where consumption of liquorice-type sweets is popular. According to our data, 10% of mothers in Helsinki are heavy consumers.2 However, because glycyrrhizin might act through cortisol-related or prostaglandin-
436
related pathways, it could possibly be used in the investigation of mechanisms causing preterm delivery. *Timo E Strandberg, Sture Andersson, Anna-Liisa Järvenpää *Department of Medicine (TES), and Department of Paediatrics (SA, A-LJ), University of Helsinki, PO Box 340, 00029 Helsinki, Finland (e-mail: [email protected]) 1 2
3
Slattery MM, Morrison JJ. Preterm delivery. Lancet 2002; 360: 1489–97. Strandberg TE, Järvenpää A-L, Vanhanen H, McKeigue PM. Birth outcome in relation to licorice consumption during pregnancy. Am J Epidemiol 2001; 153: 1085–88. Strandberg TE, Andersson Sture, Järvenpää A-L, McKeigue PM. Preterm birth and licorice consumption during pregnancy. Am J Epidemiol 2002; 156: 803–05.
Sir—In their review of the various epidemiological risk factors for preterm delivery,1 Michael Slattery and John Morrison are surprisingly discreet about dietary habits. They mention only that possible explanations for social disadvantage include worse nutritional status. Since their paper is followed by six references dated 2002, a report of the prospective cohort study by Olsen and Secher might have been included.2 Today one can claim that low consumption of seafood is the bestknown risk factor for preterm delivery. Danish pregnant women (n=8729) were interviewed about their dietary habits. The occurrence of preterm delivery differed significantly across four groups of seafood intake. Adjusted odds for preterm delivery were increased by a factor of 3·6 (95% CI 1·2–11·2) in the zero consumption group compared with the highest consumption group. Of course, Olsen and Secher assessed dietary habits that preceded to a great extent the beginning of pregnancy. This is how we explain the apparent contradiction between the Danish results and the results of our own studies: encouraging pregnant women to increase their consumption of sea fish had no effect on the duration of pregnancy.3,4 Dietary recommendations in antenatal clinics probably occur too late to have detectable effects in the perinatal period.
3
4
Odent MR, McMillan L, Kimmel T. Prenatal care and sea fish. Eur J Obstet Gynecol Reprod Biol 1996; 68: 49–51. Odent M, Colson S, De Reu P. Consumption of sea food and preterm delivery: encouraging pregnant women to eat fish did not show effect. BMJ 2002; 324: 1279.
Authors’ reply Sir—In general terms, we believe that sound conclusions about the role of nutritional factors in preterm birth are difficult to draw.1,2 We are aware of the previously published data by Timo Strandberg and colleagues3 regarding liquorice consumption during pregnancy. That study involved 95 mothers delivered preterm for any reason except twins, elective caesarean section, and induced delivery. Close scrutiny of these data indicate that further assessment of the role of liquorice in preterm birth might be appropriate before routinely advising women. First, the cases included represent a heterogeneous group of preterm births; second, the data were collected on three maternity wards by use of retrospective postnatal questionnaires—ie, many months later; and third, on statistical analysis, there was no significant difference between mothers of cases (ie, preterm birth) and mothers of controls (term birth) in terms of heavy glycyrrhizin intake (p<0·06). Michel Odent raises an interesting point in that reduced rates of preterm delivery and low birthweight have been seen in fish-eating northern European populations.4 Whether this effect (ie, significant prolongation of gestation) can be mimicked by women increasing their consumption of sea fish, and if so at a particular period of gestation, remains to be seen. Abnormal or insufficient fatty acid nutrition might have a role in adversely affecting prostaglandin and other eicosanoid metabolism. Various studies are underway to examine these issues and the potential perinatal benefits that might arise from supplementation with long-chain n-3 fatty acids.4,5 Michael M Slattery, *John J Morrison
Primal Health Research Centre, 72 Savernake Road, London NW3 2JR, UK (e-mail: [email protected])
Department of Obstetrics and Gynaecology, National University of Ireland, Galway, Republic of Ireland (MMS); and *Clinical Science Institute, University College Hospital, Newcastle Road, Galway (JJM) (e-mail: [email protected])
1
1
Michel Odent
2
Slattery MM, Morrison JJ. Preterm delivery. Lancet 2002; 360: 1489–97. Olsen S, Secher NJ. Low consumption of seafood in early pregnancy as a risk factor for preterm delivery: prospective cohort study. BMJ 2002; 324: 447.
2
Kramer MS. Nutritional advice in pregnancy (Cochrane Review). In: The Cochrane Library, issue 4. Oxford: Update Software, 2002. Cohen GR, Curet LB, Levine RJ, et al. Ethnicity, nutrition, and birth outcomes in
THE LANCET • Vol 361 • February 1, 2003 • www.thelancet.com
For personal use. Only reproduce with permission from The Lancet Publishing Group.