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Dietary fatty acids and platelet thromboxane production in puerperal women and their offspring
Dietary fatty acids and platelet thromboxane production in puerperal women and their offspring Pekka Kiipa, M.D., Matti Uhari, M.D., Tapia Nikkari, M.D., Lasse Viinikka, M.D., and Olavi Ylikorkala, M.D. Ouiu, Tampere, and Helsinki, Finland The effects of the ratio of polyunsaturated to saturated fatty acids in the diet of puerperal women on maternal and neonatal fatty acids and thromboxane A2 synthesis were studied in 91 mother-infant pairs on the fourth to fifth day after delivery. The mothers received a diet with either a low (0.1) or a high (1.5) polyunsaturated to saturated fatty acid ratio for 4 to 5 days. The fatty acid composition in maternal and neonatal serum and in breast milk was determined in 34 mother-infant pairs from both dietary groups. The capacity of the platelets to produce thromboxane B2, a stable metabolite of thromboxane A2 , was determined in another 57 mother-infant pairs. The percentage of linoleic acid was increased in maternal and neonatal sera as well as in the breast milk in the group with a high dietary polyunsaturated to saturated fatty acid ratio, whereas the content of arachidonic acid was increased only in maternal serum. This was accompanied by increased platelet thromboxane B2 production in the mothers, and maternal and neonatal thromboxane B2 synthesis correlated significantly with each other (r = 0.43, P < 0.05). This finding may provide therapeutic possibilities in the future. (AM J CasTET GVNECOL 1986;155:146-9.)
Key words: Dietary fatty acids, thromboxane A2 , thromboxane B2 , puerperal women, newborn infants
Arachidonic acid (20: 4w6) is the immediate precursor of dienoic prostaglandins and is synthesized from linoleic acid (18: 2w6) in the human body.1.2 Since humans are unable to synthesize linoleic acid, they are entirely dependent on the dietary supply oflinoleic acid and arachidonic acid! The major prostaglandin produced by the platelets is thromboxane A2 , which is a potent proaggregatory and vasoconstrictory agent that is synthesized and released during platelet aggregation. 3 • 4 In puerperal women and neonates the platelet thromboxane A2 production is higher than that in nonpregnant subjects, although the reasons for this phenomenon are unknown. 5 . 6 On the other hand, the fatty acid composition of the diet may influence thromboxane A2 synthesis,' and dietary polyunsaturated fatty acids have been reported to decrease the thromboxane A2 synthesis in vitro. 7 We compared the effects of a maternal diet with either a low (0.1) or a high (1.5) ratio of polyunsaturated to saturated fatty acids (PIS ratio) From the Departments of Pediatrics and Clinical Chemistry, University of Oulu, the Department of Biomedical Science, University of Tampere, and the Departments of Pediatrics and Obstetrics and Gynecology, University of Helsinki. The Medical Research Council, the Academy of Finland, the Finnish Heart Foundation, and the Foundation for Nutrition Research provided financial support. Received for publication October 11, 1985; revised March 10, 1986; accepted March 12, 1986. Reprint requests: Olavi Ylikorkala, M.D., Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Haartmaninkatu 2, SF-00290 Helsinki, Finland.
146
on fatty acid composition in maternal and neonatal serum and breast milk and on the maternal and neonatal platelet thromboxane A2 production.
Subjects and methods Subjects. Ninety-one mothers and their healthy neonates on two postnatal wards volunteered for this study with the approval of the local ethical committee. During a 3-week period the mothers on one puerperal ward received an ordinary hospital diet with a PIS ratio of 0.1, while the mothers on the other ward had a diet rich in vegetable oils, chicken meat and fish, vegetables, and fruits (PIS ratio 1.5). During a second 3-week period the diets on the wards were switched. The total energy intake was kept on the same level in both diets (2000 to 2200 kcal/day). The infants of mothers with ordinary and experimental diets had similar gestational ages (38.5 ± 1:2 and 38.9 ± 1.0 weeks, mean ± SD, respectively) and birth weights (3300 ± 640 and 3510 ± 550 gm, mean ± SD, respectively). The infants were breast-fed normally, and if additional breast milk was needed, it was collected from the mothers using the same diet. Samples of maternal and neonatal serum from a peripheral vein and breast milk were collected for fatty acid analysis from 34 mother-infant pairs on the fourth or fifth day of dietary intervention. On the same days maternal and neonatal serum samples by venipuncture were taken from another 57 mother-infant pairs for thromboxane A2 determinations (26 on
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Table I. The percentages of polyunsaturated and saturated fatty acids in maternal and neonatal serum and breast milk in 34 mother-infant pairs after 4 to 5 days of use of an ordinary hospital diet with PIS ratio of 0.1 or an experimental diet with PIS ratio of 1.5 Breast milk
Mother Fatty acid
14:0 16:0 18:0 18:2 18:3w6 18:3w3 20:3w6 20:4w6 20:5w3 22:6w3
Ordinary diet (mean ± SD)
1.7 24.1 6.5 26.6 0.3 0.6 1.7 4.5 0.6 2.1
± ± ± ± ± ± ± ± ± ±
0.5 1.5 0.7 5.5 0.1 0.1 0.2 0.8 0.2 0.5
Experimental diet (mean ± SD)
1.2 23.1 6.2 32.3 0.4 0.4 1.9 5.3 0.5 2.1
± ± ± ± ± ± ± ± ± ±
Experimental diet (mean ± SD)
Ordinary diet (mean ± SD)
9.1 29.2 9.4 9.1 0.1 0.6 0.5 0.6 0.1 0.6
0.3* 1.8 0.5 4.9t 0.2 0.1* 0.3:1: 1.3:1: 0.2 0.4
± ± ± ± ± ± ± ± ± ±
Infant
2.4 2.4 0.9 3.4 0.0 0.2 0.1 0.1 0.0 0.1
8.7 24.3 7.4 21.3 0.1 0.7 0.6 0.7 0.1 0.6
± ± ± ± ± ± ± ± ± ±
0.4 2.4t LOt 5.6t 0.0 0.1 O.lt 0.2 0.0 0.1
Ordinary diet (mean ± SD)
2.0 27.6 8.0 14.1 0.2 0.3 1.5 7.2 0.4 2.7
± ± ± ± ± ± ± ± ± ±
0.7 1.7 0.3 2.6 0.0 0.1 0.2 1.2 0.1 0.6
Experimental diet (mean ± SD)
1.8 26.1 7.5 18.4 0.2 0.3 1.5 7.9 0.4 2.7
± ± ± ± ± ± ± ± ± ±
0.7 2.2:1: O.4t 5.1* 0.1 0.1 0.3 1.4 0.1 0.5
*p < 0.01 in comparison with the values of the ordinary hospital diet. tp < 0.00 I in comparison with the values of the ordinary hospital diet. :l:p < 0.05 in comparison with the values of the ordinary hospital diet.
Table II. Platelet thromboxane B2 production in 57 mother-infant pairs with ordinary hospital diet (PIS ratio of 0.1) or with experimental diet (PIS ratio of 1.5) Dietary group
Thromboxane B2
Maternal serum (ng/ml) Neonatal serum (ng/ml)
Ordinary (n = 26) (mean ± SD)
Experimental (n = 31) (mean ± SD)
Difference
Confidence limits
p Value
112.5 ± 115.8
205.6 ± 132.2
93.1
90.5-95.7
<0.025
189.2 ± 106.1
233.4 ± 104.2
44.2
43.1-45.3
NS
the standard diet and 31 on the experimental diet). None of the mothers in the study had taken drugs known to interfere with prostaglandin synthesis during to days preceding the study. Methods and sampling Fatty acid analysis. Aliquots of milk or serum (100 to 200 fl.l) were extracted with chloroform-methanol (1 : I, v/v). The extract was purified, evaporated, and saponified in potassium hydroxide-ethanol (0.5 moIlL), as described in detail previously.8 After extraction of the nonpolar material with petroleum ether (boiling point 60° to 80° C), the lower phase was acidified with hydrochloric acid and the fatty acids were extracted into petroleum ether. The solvent was evaporated and the fatty acids were esterified with hydrochloric acid-methanol. 8 The methyl esters were analyzed in a HewlettPackard 6880A gas chromatograph with the use of an open tubular fused silica column 25 m long and 0.32 mm inside diameter coated with OV-351 (Orion Analytica, Espoo, Finland) and a flame ionization detector. All peaks corresponding to fatty acids from 14: 0 to 22:6 were quantified with a Hewlett-Packard 6880A
integrator. The results were expressed as percentages of the total area of all identified fatty acid peaks. Thromboxane A2 measurement. To study the ability of the platelets to generate thromboxane A2 during spontaneous clotting, a blood sample (3 to 5 ml) was drawn from both mothers and infants into a dry test tube and allowed to clot at 37° C for 60 minutes. The concentration of thromboxane B2, a hydration product of thromboxane A2, in serum was then measured radioimmunologically. 9 Statistical analyses. Because of the abnormal distribution of the thromboxane B2 values, thromboxane B2 data were transformed logarithmically and the significances of the differences were tested with Student's t test. Pearson's correlation coefficient was calculated between the thromboxane B2 values of the mothers and their infants. The results are expressed as means and SDs. Results
A maternal diet with a high PIS ratio was accompanied with an increased content of linoleic acid, dihomo-
148 Kaapa et al.
'Y-linoleic acid, and arachidonic acid in the serum of the mothers and increased proportions of linoleic acid and dihomo-'Y-linoleic acid in the breast milk (Table I). Linoleic acid was also increased in neonatal serum (Table I). Ingestion of a diet with a high PIS ratio resulted in increased production of thromboxane B2 by maternal but not neonatal platelets (Table II), although maternal and neonatal thromboxane B2 production capacities were related to each other (r = 0.43, P < 0.05). A similar trend was also seen in mother-infant pairs with ordinary diet (r = 0.38,0.1 > P > 0.05).
Comment Dietary manipulation of the supply of fatty acids may have important clinical consequences, I which also involve the breast-fed infants. We present evidence that a short-term (4 to 5 days) change in the maternal dietary PIS ratio is already reflected in the fatty acid composition of breast milk andlor neonatal serum. This is in agreement with previous data showing that administration of polyunsaturated fatty acids to mothers increases their percentages in serum lipids but decreases the content of cholesterol in the maternal and neonatal blood. I. 10. II These changes, on the other hand, could be important in the prevention of vascular atherogenesis, possibly through changes in the prostanoid biosynthesis. 12 In our study a rise in the dietary PIS ratio from 0.1 to 1.5 increased the proportions of the precursors of dienoic prostaglandins (linoleic acid, dihomo-'Y-linoleic acid, and arachidonic acid), whereas the concentration of a-linoleic acid (18: 3w3) was decreased in the mothers. Because the latter can also be converted to eicosapentaenoic acid (20: 5w3) in man,13 its reduction may cause a decrease in the synthesis of trienoic prostaglandins. 14 Because of the competition between the syntheses of series 2 and 3 prostaglandins, this change should result in increased production of series 2 prostanoids, and, indeed, maternal platelet thromboxane B2 production was increased during the dietary interventiOli. On the other hand, there was no decrease in the proportion of eicosapentaenoic acid in our experiment (Table I). In the infants the change of maternal diet resulted in an increase in the serum linoleic acid, whereas the thromboxane B2 production was unchanged. There was, however, a correlation between maternal and neonatal thromboxane B2 productions, which suggests that perhaps a more profound dietary intervention could have also increased the neonatal thromboxane B2 synthesis. Previous studies on non puerperal subjects have shown that platelet aggregation decreases after ingestion of diets rich in polyunsaturated fatty acids, espe-
July, 1986 Am J Obstet Gynecol
cially linoleic acid. 15. 16 Our finding of an increased production of proaggregatory and vasoconstrictory thromboxane A2 in puerperal women with a high dietary PIS ratio is in apparent discrepancy with these results. There may be several explanations for the discrepancy: (1) The diets in different studies have not been standardized. Varying amounts of fatty acids other than linoleic acid, for instance, arachidonic acid and eicosapentaenoic acid, may lead to different results in both platelet aggregation and thromboxane A2 production. (2) The production of thromboxane A2 may not relate directly to the aggregation of the platelets. Other diet-dependent factors, such as a change in membrane fluidity, production of the antiaggregatory prostaglandin EI from dihomo-'Y-linoleic acid, and the balance between thromboxane A2 and its biologic antagonist prostacyclin, may influence the aggregation process. I. 2 (3) We studied puerperal women, whose thromboxane B2 production is increased 5 and who may respond differently to the dietary changes in PIS ratio. These changes may also be sex-dependent, since such a dietary manipulation decreases the thromboxane B2 production in men but tends to increase it in women. 12 The clinical significance of the increased thromboxane A2 synthesis remains unknown. Prostanoids are hemodynamically important during the early neonatal period. 6 It is possible that their metabolism could be affected by changing the supply of fatty acids to the newborn infant through alterations in the maternal diet, as is evident from our data. Thus maternal dietary manipulation may offer new possibilities for treatment and prevention of various neonatal disorders.
REFERENCES 1. Friedman Z. Essential fatty acids revisited. Am] Dis Child 1980; 134:397-408. 2. Ramwell PW, Foegh M, Loeb R, Leovey EMK. Synthesis and metabolism of prostaglandins, prostacyclin and thromboxanes: the arachidonic acid cascade. Semin Perinatol 1980;4:3-13. 3. Hamberg M, Svensson ], Samuelsson B. Prostaglandin endoperoxides. A new concept concerning the mode of action and release of prostaglandins. Proc Nat! Acad Sci USA 1974;71:3824-8. 4. Hamberg M, Svensson], Samuelsson B. Thromboxanes: a new group of biologically active compounds derived from prostaglandin endoperoxides. Proc Nat! Acad Sci USA 1975;72:2994-8. 5. Ylikorkala 0, Viinikka L. Thromboxane A2 in pregnancy and puerperium. Br Med] 1980;281:1601-2. 6. Kaapa P, Viinikka L, Ylikorkala O. Thromboxane B2 production by fetal and neonatal platelets: effect of idiopathic respiratory distress syndrome and birth asphyxia. Pediatr Res 1984; 18:756-8. 7. Schoene NW,]udd]T, Marshall MW, Reeves V, Carvalho A. Effects of diets varying in fat and PIS ratio on arachidonic acid metabolism in human platelets. Adv Prostaglandin Thromboxane Res 1980;8: 1787-8. 8. Moilanen T, Nikkari T. The effect of storage on the fatty
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9. 10.
II.
12.
acid composlUon of human serum. Clin Chim Acta 1981; 114: 111-6. Viinikka L, Ylikorkala 0. Measurement of thromboxane B2 in human plasma or serum by radioimmunoassay. Prostaglandins 1980;20:759-66. Mellies Mj, Ishikawa TT, Gartside PS, et al. Effects of varying maternal dietary fatty acids in lactating women and their infants. Am j Clin Nutr 1979;32:299-303. Potter jM, Nestel PJ. The effects of dietary fatty acids and cholesterol on the milk lipids of lactating women and the plasma cholesterol of breast-fed infants. Am j Clin Nutr 1976;29:54-60. Tremoli E, Petroni A, Galli C, et al. North Karelian study: changes in dietary fat reduce thromboxane B, formation by platelets only in male subjects. Preliminary report. Adv Prostaglandin Thromboxane Leukotriene 1983; 12:203-7.
13. Sanders TAB, Younger KM. The effect of dietary supplement of w3 polyunsaturated fatty acids on fatty acid composition of platelets and plasma choline phosphoglycerides. Br j Nutr 1981;45:613-6. 14. Needleman P, Raz A, Minkes MS, Ferrendelli jA, Sprecher H. Triene prostaglandins: prostacyclin and thromboxane biosynthesis and unique biological properties. Proc Nat! Acad Sci USA 1979;76:944-8. 15. Hornstra G, Chait A, Karvonen Mj, Lewis B, Turpeinen 0, Vergroesen AJ. Influence of dietary fat on platelet function in men. Lancet 1973;1:1155-7. 16. O'BrienjR, Etherington MD,jamieson S, Vergroesen Aj, Ten Hoor F. Effect of a diet of polyunsaturated fats on some platelet function tests. Lancet 1976;2:995-7.
The use of the nonstress test in patients with premature rupture of the membranes Anthony M. Vintzileos, M.D., Winston A. Campbell, M.D., David J. Nochimson, M.D., and Paul J. Weinbaum, M.D. Farmington, Connecticut The value of the nonstress test in predicting the outcome of infection was determined by a retrospective analysis of 127 consecutive high-risk patients who presented with premature rupture of the membranes and no clinical signs of infection or labor. The last study performed within 48 hours of delivery was used for comparison with the outcome of pregnancy. The relationship between nonstress test results and the outcome of pregnancy, as reflected by the development of clinical amnionitis and/or neonatal sepsis, was determined. The sensitivity and specificity of the nonstress test in predicting infection outcome in patients with premature rupture of the membranes were 78.1 % and 86.3%, respectively. These data suggest that the nonstress test is a useful tool for evaluating patients with premature rupture of the membranes. (AM J OBSTET GVNECOL 1986;155:149-53.)
Key words: Nonstress test, premature rupture of membranes Premature rupture of the membranes is one of the most common complications of pregnancy. It occurs in approximately 10% of all pregnancies I and is associated with an increased incidence of perinatal death,2 fetal distress during labor,' and infection (maternal and fetal).' Since the contraction stress test is contraindicated in the presence of ruptured membranes, antepartum fetal evaluation of these patients has been confined solely to nonstress testing. The value of the nonstress test has been well documented in high-risk patients with
From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, The University of Connecticut Health Center. Received for publication October 2, 1985; accepted March 3,
1986. Reprint requests: Dr. Anthony M. Vintzileos, Division of MaternalFetal Medicine, Department of Obstetrics and Gynecology, The University of Connecticut Health Center, Farmington, CT 06032.
intact membranes""; however, its value in the antepartum fetal surveillance of patients with premature rupture of the membranes has not been determined accurately. The fetal biophysical profile has been described' recently by the authors as an early predictor of impending infection in patients with premature rupture of the membranes. In that report' a tendency for a higher incidence of infection with nonreactive nonstress testing was observed. Since the nonstress test is most frequently used as a primary antepartum fetal surveillance test, the present retrospective study was undertaken to determine the value of the nonstress test in evaluating patients who presented with premature rupture of the membranes and no clinical signs of infection or labor. Measures of pregnancy outcome included the presence of clinical amnionitis, possible neonatal sepsis, and neonatal sepsis.
149
Key words: Dietary fatty acids, thromboxane A2 , thromboxane B2 , puerperal women, newborn infants
Arachidonic acid (20: 4w6) is the immediate precursor of dienoic prostaglandins and is synthesized from linoleic acid (18: 2w6) in the human body.1.2 Since humans are unable to synthesize linoleic acid, they are entirely dependent on the dietary supply oflinoleic acid and arachidonic acid! The major prostaglandin produced by the platelets is thromboxane A2 , which is a potent proaggregatory and vasoconstrictory agent that is synthesized and released during platelet aggregation. 3 • 4 In puerperal women and neonates the platelet thromboxane A2 production is higher than that in nonpregnant subjects, although the reasons for this phenomenon are unknown. 5 . 6 On the other hand, the fatty acid composition of the diet may influence thromboxane A2 synthesis,' and dietary polyunsaturated fatty acids have been reported to decrease the thromboxane A2 synthesis in vitro. 7 We compared the effects of a maternal diet with either a low (0.1) or a high (1.5) ratio of polyunsaturated to saturated fatty acids (PIS ratio) From the Departments of Pediatrics and Clinical Chemistry, University of Oulu, the Department of Biomedical Science, University of Tampere, and the Departments of Pediatrics and Obstetrics and Gynecology, University of Helsinki. The Medical Research Council, the Academy of Finland, the Finnish Heart Foundation, and the Foundation for Nutrition Research provided financial support. Received for publication October 11, 1985; revised March 10, 1986; accepted March 12, 1986. Reprint requests: Olavi Ylikorkala, M.D., Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Haartmaninkatu 2, SF-00290 Helsinki, Finland.
146
on fatty acid composition in maternal and neonatal serum and breast milk and on the maternal and neonatal platelet thromboxane A2 production.
Subjects and methods Subjects. Ninety-one mothers and their healthy neonates on two postnatal wards volunteered for this study with the approval of the local ethical committee. During a 3-week period the mothers on one puerperal ward received an ordinary hospital diet with a PIS ratio of 0.1, while the mothers on the other ward had a diet rich in vegetable oils, chicken meat and fish, vegetables, and fruits (PIS ratio 1.5). During a second 3-week period the diets on the wards were switched. The total energy intake was kept on the same level in both diets (2000 to 2200 kcal/day). The infants of mothers with ordinary and experimental diets had similar gestational ages (38.5 ± 1:2 and 38.9 ± 1.0 weeks, mean ± SD, respectively) and birth weights (3300 ± 640 and 3510 ± 550 gm, mean ± SD, respectively). The infants were breast-fed normally, and if additional breast milk was needed, it was collected from the mothers using the same diet. Samples of maternal and neonatal serum from a peripheral vein and breast milk were collected for fatty acid analysis from 34 mother-infant pairs on the fourth or fifth day of dietary intervention. On the same days maternal and neonatal serum samples by venipuncture were taken from another 57 mother-infant pairs for thromboxane A2 determinations (26 on
Dietary fats and platelet thromboxane in puerperium
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Table I. The percentages of polyunsaturated and saturated fatty acids in maternal and neonatal serum and breast milk in 34 mother-infant pairs after 4 to 5 days of use of an ordinary hospital diet with PIS ratio of 0.1 or an experimental diet with PIS ratio of 1.5 Breast milk
Mother Fatty acid
14:0 16:0 18:0 18:2 18:3w6 18:3w3 20:3w6 20:4w6 20:5w3 22:6w3
Ordinary diet (mean ± SD)
1.7 24.1 6.5 26.6 0.3 0.6 1.7 4.5 0.6 2.1
± ± ± ± ± ± ± ± ± ±
0.5 1.5 0.7 5.5 0.1 0.1 0.2 0.8 0.2 0.5
Experimental diet (mean ± SD)
1.2 23.1 6.2 32.3 0.4 0.4 1.9 5.3 0.5 2.1
± ± ± ± ± ± ± ± ± ±
Experimental diet (mean ± SD)
Ordinary diet (mean ± SD)
9.1 29.2 9.4 9.1 0.1 0.6 0.5 0.6 0.1 0.6
0.3* 1.8 0.5 4.9t 0.2 0.1* 0.3:1: 1.3:1: 0.2 0.4
± ± ± ± ± ± ± ± ± ±
Infant
2.4 2.4 0.9 3.4 0.0 0.2 0.1 0.1 0.0 0.1
8.7 24.3 7.4 21.3 0.1 0.7 0.6 0.7 0.1 0.6
± ± ± ± ± ± ± ± ± ±
0.4 2.4t LOt 5.6t 0.0 0.1 O.lt 0.2 0.0 0.1
Ordinary diet (mean ± SD)
2.0 27.6 8.0 14.1 0.2 0.3 1.5 7.2 0.4 2.7
± ± ± ± ± ± ± ± ± ±
0.7 1.7 0.3 2.6 0.0 0.1 0.2 1.2 0.1 0.6
Experimental diet (mean ± SD)
1.8 26.1 7.5 18.4 0.2 0.3 1.5 7.9 0.4 2.7
± ± ± ± ± ± ± ± ± ±
0.7 2.2:1: O.4t 5.1* 0.1 0.1 0.3 1.4 0.1 0.5
*p < 0.01 in comparison with the values of the ordinary hospital diet. tp < 0.00 I in comparison with the values of the ordinary hospital diet. :l:p < 0.05 in comparison with the values of the ordinary hospital diet.
Table II. Platelet thromboxane B2 production in 57 mother-infant pairs with ordinary hospital diet (PIS ratio of 0.1) or with experimental diet (PIS ratio of 1.5) Dietary group
Thromboxane B2
Maternal serum (ng/ml) Neonatal serum (ng/ml)
Ordinary (n = 26) (mean ± SD)
Experimental (n = 31) (mean ± SD)
Difference
Confidence limits
p Value
112.5 ± 115.8
205.6 ± 132.2
93.1
90.5-95.7
<0.025
189.2 ± 106.1
233.4 ± 104.2
44.2
43.1-45.3
NS
the standard diet and 31 on the experimental diet). None of the mothers in the study had taken drugs known to interfere with prostaglandin synthesis during to days preceding the study. Methods and sampling Fatty acid analysis. Aliquots of milk or serum (100 to 200 fl.l) were extracted with chloroform-methanol (1 : I, v/v). The extract was purified, evaporated, and saponified in potassium hydroxide-ethanol (0.5 moIlL), as described in detail previously.8 After extraction of the nonpolar material with petroleum ether (boiling point 60° to 80° C), the lower phase was acidified with hydrochloric acid and the fatty acids were extracted into petroleum ether. The solvent was evaporated and the fatty acids were esterified with hydrochloric acid-methanol. 8 The methyl esters were analyzed in a HewlettPackard 6880A gas chromatograph with the use of an open tubular fused silica column 25 m long and 0.32 mm inside diameter coated with OV-351 (Orion Analytica, Espoo, Finland) and a flame ionization detector. All peaks corresponding to fatty acids from 14: 0 to 22:6 were quantified with a Hewlett-Packard 6880A
integrator. The results were expressed as percentages of the total area of all identified fatty acid peaks. Thromboxane A2 measurement. To study the ability of the platelets to generate thromboxane A2 during spontaneous clotting, a blood sample (3 to 5 ml) was drawn from both mothers and infants into a dry test tube and allowed to clot at 37° C for 60 minutes. The concentration of thromboxane B2, a hydration product of thromboxane A2, in serum was then measured radioimmunologically. 9 Statistical analyses. Because of the abnormal distribution of the thromboxane B2 values, thromboxane B2 data were transformed logarithmically and the significances of the differences were tested with Student's t test. Pearson's correlation coefficient was calculated between the thromboxane B2 values of the mothers and their infants. The results are expressed as means and SDs. Results
A maternal diet with a high PIS ratio was accompanied with an increased content of linoleic acid, dihomo-
148 Kaapa et al.
'Y-linoleic acid, and arachidonic acid in the serum of the mothers and increased proportions of linoleic acid and dihomo-'Y-linoleic acid in the breast milk (Table I). Linoleic acid was also increased in neonatal serum (Table I). Ingestion of a diet with a high PIS ratio resulted in increased production of thromboxane B2 by maternal but not neonatal platelets (Table II), although maternal and neonatal thromboxane B2 production capacities were related to each other (r = 0.43, P < 0.05). A similar trend was also seen in mother-infant pairs with ordinary diet (r = 0.38,0.1 > P > 0.05).
Comment Dietary manipulation of the supply of fatty acids may have important clinical consequences, I which also involve the breast-fed infants. We present evidence that a short-term (4 to 5 days) change in the maternal dietary PIS ratio is already reflected in the fatty acid composition of breast milk andlor neonatal serum. This is in agreement with previous data showing that administration of polyunsaturated fatty acids to mothers increases their percentages in serum lipids but decreases the content of cholesterol in the maternal and neonatal blood. I. 10. II These changes, on the other hand, could be important in the prevention of vascular atherogenesis, possibly through changes in the prostanoid biosynthesis. 12 In our study a rise in the dietary PIS ratio from 0.1 to 1.5 increased the proportions of the precursors of dienoic prostaglandins (linoleic acid, dihomo-'Y-linoleic acid, and arachidonic acid), whereas the concentration of a-linoleic acid (18: 3w3) was decreased in the mothers. Because the latter can also be converted to eicosapentaenoic acid (20: 5w3) in man,13 its reduction may cause a decrease in the synthesis of trienoic prostaglandins. 14 Because of the competition between the syntheses of series 2 and 3 prostaglandins, this change should result in increased production of series 2 prostanoids, and, indeed, maternal platelet thromboxane B2 production was increased during the dietary interventiOli. On the other hand, there was no decrease in the proportion of eicosapentaenoic acid in our experiment (Table I). In the infants the change of maternal diet resulted in an increase in the serum linoleic acid, whereas the thromboxane B2 production was unchanged. There was, however, a correlation between maternal and neonatal thromboxane B2 productions, which suggests that perhaps a more profound dietary intervention could have also increased the neonatal thromboxane B2 synthesis. Previous studies on non puerperal subjects have shown that platelet aggregation decreases after ingestion of diets rich in polyunsaturated fatty acids, espe-
July, 1986 Am J Obstet Gynecol
cially linoleic acid. 15. 16 Our finding of an increased production of proaggregatory and vasoconstrictory thromboxane A2 in puerperal women with a high dietary PIS ratio is in apparent discrepancy with these results. There may be several explanations for the discrepancy: (1) The diets in different studies have not been standardized. Varying amounts of fatty acids other than linoleic acid, for instance, arachidonic acid and eicosapentaenoic acid, may lead to different results in both platelet aggregation and thromboxane A2 production. (2) The production of thromboxane A2 may not relate directly to the aggregation of the platelets. Other diet-dependent factors, such as a change in membrane fluidity, production of the antiaggregatory prostaglandin EI from dihomo-'Y-linoleic acid, and the balance between thromboxane A2 and its biologic antagonist prostacyclin, may influence the aggregation process. I. 2 (3) We studied puerperal women, whose thromboxane B2 production is increased 5 and who may respond differently to the dietary changes in PIS ratio. These changes may also be sex-dependent, since such a dietary manipulation decreases the thromboxane B2 production in men but tends to increase it in women. 12 The clinical significance of the increased thromboxane A2 synthesis remains unknown. Prostanoids are hemodynamically important during the early neonatal period. 6 It is possible that their metabolism could be affected by changing the supply of fatty acids to the newborn infant through alterations in the maternal diet, as is evident from our data. Thus maternal dietary manipulation may offer new possibilities for treatment and prevention of various neonatal disorders.
REFERENCES 1. Friedman Z. Essential fatty acids revisited. Am] Dis Child 1980; 134:397-408. 2. Ramwell PW, Foegh M, Loeb R, Leovey EMK. Synthesis and metabolism of prostaglandins, prostacyclin and thromboxanes: the arachidonic acid cascade. Semin Perinatol 1980;4:3-13. 3. Hamberg M, Svensson ], Samuelsson B. Prostaglandin endoperoxides. A new concept concerning the mode of action and release of prostaglandins. Proc Nat! Acad Sci USA 1974;71:3824-8. 4. Hamberg M, Svensson], Samuelsson B. Thromboxanes: a new group of biologically active compounds derived from prostaglandin endoperoxides. Proc Nat! Acad Sci USA 1975;72:2994-8. 5. Ylikorkala 0, Viinikka L. Thromboxane A2 in pregnancy and puerperium. Br Med] 1980;281:1601-2. 6. Kaapa P, Viinikka L, Ylikorkala O. Thromboxane B2 production by fetal and neonatal platelets: effect of idiopathic respiratory distress syndrome and birth asphyxia. Pediatr Res 1984; 18:756-8. 7. Schoene NW,]udd]T, Marshall MW, Reeves V, Carvalho A. Effects of diets varying in fat and PIS ratio on arachidonic acid metabolism in human platelets. Adv Prostaglandin Thromboxane Res 1980;8: 1787-8. 8. Moilanen T, Nikkari T. The effect of storage on the fatty
Dietary fats and platelet thromboxane in puerperium
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9. 10.
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acid composlUon of human serum. Clin Chim Acta 1981; 114: 111-6. Viinikka L, Ylikorkala 0. Measurement of thromboxane B2 in human plasma or serum by radioimmunoassay. Prostaglandins 1980;20:759-66. Mellies Mj, Ishikawa TT, Gartside PS, et al. Effects of varying maternal dietary fatty acids in lactating women and their infants. Am j Clin Nutr 1979;32:299-303. Potter jM, Nestel PJ. The effects of dietary fatty acids and cholesterol on the milk lipids of lactating women and the plasma cholesterol of breast-fed infants. Am j Clin Nutr 1976;29:54-60. Tremoli E, Petroni A, Galli C, et al. North Karelian study: changes in dietary fat reduce thromboxane B, formation by platelets only in male subjects. Preliminary report. Adv Prostaglandin Thromboxane Leukotriene 1983; 12:203-7.
13. Sanders TAB, Younger KM. The effect of dietary supplement of w3 polyunsaturated fatty acids on fatty acid composition of platelets and plasma choline phosphoglycerides. Br j Nutr 1981;45:613-6. 14. Needleman P, Raz A, Minkes MS, Ferrendelli jA, Sprecher H. Triene prostaglandins: prostacyclin and thromboxane biosynthesis and unique biological properties. Proc Nat! Acad Sci USA 1979;76:944-8. 15. Hornstra G, Chait A, Karvonen Mj, Lewis B, Turpeinen 0, Vergroesen AJ. Influence of dietary fat on platelet function in men. Lancet 1973;1:1155-7. 16. O'BrienjR, Etherington MD,jamieson S, Vergroesen Aj, Ten Hoor F. Effect of a diet of polyunsaturated fats on some platelet function tests. Lancet 1976;2:995-7.
The use of the nonstress test in patients with premature rupture of the membranes Anthony M. Vintzileos, M.D., Winston A. Campbell, M.D., David J. Nochimson, M.D., and Paul J. Weinbaum, M.D. Farmington, Connecticut The value of the nonstress test in predicting the outcome of infection was determined by a retrospective analysis of 127 consecutive high-risk patients who presented with premature rupture of the membranes and no clinical signs of infection or labor. The last study performed within 48 hours of delivery was used for comparison with the outcome of pregnancy. The relationship between nonstress test results and the outcome of pregnancy, as reflected by the development of clinical amnionitis and/or neonatal sepsis, was determined. The sensitivity and specificity of the nonstress test in predicting infection outcome in patients with premature rupture of the membranes were 78.1 % and 86.3%, respectively. These data suggest that the nonstress test is a useful tool for evaluating patients with premature rupture of the membranes. (AM J OBSTET GVNECOL 1986;155:149-53.)
Key words: Nonstress test, premature rupture of membranes Premature rupture of the membranes is one of the most common complications of pregnancy. It occurs in approximately 10% of all pregnancies I and is associated with an increased incidence of perinatal death,2 fetal distress during labor,' and infection (maternal and fetal).' Since the contraction stress test is contraindicated in the presence of ruptured membranes, antepartum fetal evaluation of these patients has been confined solely to nonstress testing. The value of the nonstress test has been well documented in high-risk patients with
From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, The University of Connecticut Health Center. Received for publication October 2, 1985; accepted March 3,
1986. Reprint requests: Dr. Anthony M. Vintzileos, Division of MaternalFetal Medicine, Department of Obstetrics and Gynecology, The University of Connecticut Health Center, Farmington, CT 06032.
intact membranes""; however, its value in the antepartum fetal surveillance of patients with premature rupture of the membranes has not been determined accurately. The fetal biophysical profile has been described' recently by the authors as an early predictor of impending infection in patients with premature rupture of the membranes. In that report' a tendency for a higher incidence of infection with nonreactive nonstress testing was observed. Since the nonstress test is most frequently used as a primary antepartum fetal surveillance test, the present retrospective study was undertaken to determine the value of the nonstress test in evaluating patients who presented with premature rupture of the membranes and no clinical signs of infection or labor. Measures of pregnancy outcome included the presence of clinical amnionitis, possible neonatal sepsis, and neonatal sepsis.
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