The effect of pregnancy on metabolic responses during rest, immersion, and aerobic exercise in the water

The effect of pregnancy on metabolic responses during rest, immersion, and aerobic exercise in the water

The effect of pregnancy on metabolic responses during rest, immersion, and aerobic exercise in the water R. G. McMurray, PhD, V. L. Katz, MD, M. J. Be...

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The effect of pregnancy on metabolic responses during rest, immersion, and aerobic exercise in the water R. G. McMurray, PhD, V. L. Katz, MD, M. J. Berry, PhD, and R. C. Cefalo, MD, PhD Chapel Hill, North Carolina To examine the effects of advancing pregnancy on metabolic responses, 12 women, who were recruited early in pregnancy, were studied during 20 minutes of immersion in 30° C water, followed by 20 minutes of exercise in the water (60% of predicted maximal capacity) and 20 minutes of lateral supine recovery. Each subject completed the trials during the fifteenth, twenty-fifth, and thirty-fifth weeks of pregnancy, as well as a control period 8 to 10 weeks postpartum. Resting oxygen uptake increased with advancing pregnancy. Resting oxygen uptake was higher in the water than on land but was not altered by pregnancy. Exercise oxygen uptakes were similar for all trials, but the work load required to elicit the Vo2 decreased during the thirty-fifth week of pregnancy. Exercise heart rates followed the same pattern as oxygen uptake. Lactate concentrations declined with advancing pregnancy after exercise. Blood glucose levels were normal for pregnancy but declined slightly during exercise. Blood triglyceride levels were elevated with exercise, with a tendency to increase with advancing pregnancy. Resting plasma cortisol concentrations increased with pregnancy but remained lower during immersion and exercise. These results suggest that pregnancy significantly alters metabolic responses to exercise in the water. (AM J OBSTET GYNECOL 1988;158:481-6.)

Key words: Pregnancy, exercise, immersion, oxygen uptake, heart rate, lactate, glucose, triglyceride, cortisol

Artal and Wiswell' and Katz• have suggested that swimming may be the perfect aerobic activity for pregnant women because the bouyant effect of the water supports the weight of the woman and provides a favorable medium for heat dissipation. Knuttgen and Emerson' and Pernoll et al.4 have demonstrated that the energy cost of weight-bearing exercise is increased in the pregnant woman. Conversely, Seitchik' has previously noted that the energy cost of non-weightbearing exercise is similar for pregnant and nonpregnant women. The bouyant effect of water suggests that immersion exercise is non-weight bearing. Therefore the metabolic rate would be expected to be unaffected by pregnancy status. Although practitioners have advocated exercise in the water, be it swimming or water calisthentics, little evidence exists concerning the metabolic response of pregnant women during immersion or exercise in the water. Studies on the metabolic responses of gravid women during mild land exercise have indicated that fats are the primary source of energy, but blood glucose levels may be somewhat reduced. 6 Moderate levels of exertion increase the contribution of carbohydrates and

From the Exercise Physiology Laboratory and Division of Maternal and Fetal Medicine, Department of Obstetrics, University of North Carolina. Received for publication July 10, 1987; revised August 19, 1987; accepted September 22, 1987. Reprint requests: Robert G. McMurray, PhD, Physical Education Department, University of North Carolina, Chapel Hill, NC 27514.

thus further reduce blood glucose levels.'·" Other studies'·•. 7 that used R values to indicate substrate use have also suggested an increase in carbohydrate use. The results of animal studies have found that moderate exercise results in a reduction in blood glucose, which leads to a rapid depletion of muscle glycogen." In constrast, Artal et al. 6 and Lotgering et al." suggest that blood glucose levels are not affected by moderate intensity exercise. No data were available on the metabolic responses during exercise in the water. Glucocorticoids levels increase throughout pregnancy but seem to have little response during exercise on land. 1. 10 Since cold is known to elevate cortisol levels, 11 the question remains whether immersion or exercise in water that is lower than body temperature affects this response. Thus the purpose of this study was to examine metabolic responses of pregnant women during immersion and exercise in water, and more specifically, to examine these responses as they occur with advancing pregnancy and compare them with those occurring 10 weeks postpartum, with each subject serving as her own control.

Methods Twelve women were recruited early in their pregnancies. The subjects averaged 30 ± 3 years of age, 164 ± 5 cm in height, and had a nonpregnant weight of approximately 62.4 ± 8.2 kg. Physical examination indicated that the women were free of pregnancy complications and had no exercise limitations. All the women considered themselves active, but only two par481

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March 1988 Am J Obstet Gynecol

Table I. The effect of pregnancy status on oxygen uptake, heart rate, and hematocrit (mean ± SEM) 15 weeks

25 weeks

35 weeks

Postpartum

0.20 ± 0.03 0.43 ± 0.06 1.16 ± 0.14

0.26 :'.. 0.03 0.45 ± 0.03 1.18 ± 0.17

0.28 ± 0.04 0.39 ± 0.02 0.12 ± 0.20

0.20 ± 0.03 0.31 ± 0.02 1.20 ± 0.13

86 ± 2 82 ± 4 134 ± 4

89 ± 2 83 ± 3 133 ± 4

92 ± 3 84 ± 4 131 ± 4

69 ± 3 62 ± 3 128 ± 2

34.1 ± 0.5 33.2 ± 0.4 34.7 ± 0.4

32.9 ± 0.6 31.9 ± 0.6 33.8 ± 0.7

34.2 ± 0.6 33.5 ± 0.7 34.5 ± 0.7

38.9 ± 0.7 38.9 ± 0.7 40.8 ± 0.7

V02 (L/min) Rest Immersion Exercise Heart rate (bpm) Rest Immersion Exercise Hematocrit (%) Rest Immersion Exercise

ticipated in a regular fitness program consisting of aerobics or tennis. All signed an informed consent approved by the Committee on the Rights of Human Subjects. All subjects were tested during the fifteenth, twentyfifth, and thirty-fifth week of pregnancy and 8 to IO weeks' postpartum following the same procedures. The testing consisted of two trials. During the first trial, each subject completed a graduated exercise bout on land to determine the work load equal to 60% of their predicted maximal capacity to be used for the subsequent water trial. This intensity of exercise was chosen on the basis of pilot testing, which indicated that most pregnant women could not pedal the ergometer in the water for 20 minutes at a higher intensity. The subjects reported to the laboratory and were weighed, and electrocardiographic leads were attached using a CM-5 arrangement. The subject was then moved to the bicycle ergometer and began to pedal with zero load. The work load was increased by 12 to 25 W every 3 minutes until the subject had attained a heart rate equal to 60% of her predicted maximal heart rate (0.6[220 - Age - HR rest] + HR rest). This work load was then maintained for I minute while oxygen uptake was measured. The Vo 2 was then entered into the regression equation of Morlock and Dressendorfer 12 to obtain the correct pedal frequency to be used for exercise ergometer testing in the water. The water trials consisted of a 20-minute lateral supine rest on land, 20 minutes of rest immersed to the level of the xiphoid, followed immediately by 20 minutes of exercise at the predetermined pedal frequency (Vo2). Immersion and exercise were completed in a tank that contained 68 cu ft of water, with the temperature of the tank maintained at 30 ± 0.2° C. Exercise was performed on a bicycle ergometer as modified by Morlock and Dressendorfer. 12 This modification removes the friction belt apparatus and relies on pedal frequency to provide the resistance (work load). This method was chosen because bicycling has been found to be independent of weight' and allowed us to have full control over the subject while in the water.

Risch et al." have also shown that immersion to the level of the xiphoid causes changes in the heart similar to those with horizontal swimming. The subject reported in shorts and shirt to the laboratory, was weighed, electrocardiographic leads were attached, and began a 20-minute rest on land while lying on her side covered by a blanket to reduce possible cooling. After 20 minutes, the subject's resting metabolic rate was measured for 7 minutes. Once the resting metabolic rate was completed, a 20-gauge catheter was inserted into an antecubital vein, and a 20 ml resting blood sample was obtained. The subject then entered the water tank and seated herself on a bicycle ergometer where she rested for 20 minutes. Oxygen uptake was measured during the nineteenth minute of immersion, and a 20 ml blood sample was obtained during the twentieth minute. At the end of the immersion rest, the subject began pedaling the bicycle ergometer at the predetermined pedal frequency and continued at that frequency for 20 minutes. During the exercise period, oxygen uptake was measured every 5 minutes. Electrocardiogram was continuously monitored via an oscilloscope and recorded the last IO seconds of each minute. At the end of exercise, a 20 ml blood sample was again obtained. The subject was then assisted out of the tank and moved to a cot where she rested on her side for 20 minutes. Heart rate was taken at 5-minute intervals, and a 20 ml blood sample was obtained at the end of the rest period. The subject was then weighed. To ascertain the correct weight, the weight of the dry clothing was subtracted from the initial weight, and the weight of the wet clothing was subtracted from the final weight.

Instrumentation Resting metabolic rate and exercise oxygen uptake were measured by open circuit spirometry. During rest, the subject breathed through a small-bore HansRudolph valve, with the expired side connected to a meterologic bag to collect the full 7 minutes of expiration. The contents of the bag were then analyzed

Exercise anq pregnancy 483

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IMMERSION EXERCISE RECOVERY

Fig. 2. Plasma cortisol responses (mean ± SEM) at rest, during immersion, at the end of exercise, and after 20 minutes of recovery in relation to pregnancy status: (•) 15 weeks, (•) 25 weeks, (A) 35 weeks, (O) postpartum. p < 0.05 postpartum versus 15, 25, or 35 weeks; p < 0.05 15 weeks versus 25 or 35 weeks; p < 0.05 rest versus immersion, exercise, or recovery.

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I- 100 IMMERSION EXERCISE RECOVERY Fig. 1. Mean ± SEM plasma lactate, glucose, and triglyceride concentrations during rest, immersion, exercise (60% Vo2 max), and recovery with respect to pregnancy status. (PP = Postpartum.)

for oxygen and carbon dioxide content by means of an Applied Electrochemistry oxygen analyzer and a Beckman LB-2 carbon dioxide analyzer. The volume of the air in the bag was measured by a ParkinsonCowen dry gas meter and divided by seven to obtain minute ventilation. During the water trials, the subject breathed through a Collins Triple-] valve. The inspired side of the valve was connected to a dry gas meter to obtain measurements of inspired minute ventilation. The expired side of the valve was connected to a mixing chamber from which expired oxygen and carbon dioxide were monitored by the previously analyzers. Oxygen uptake and carbon dioxide output were calculated from the minute ventilation and expired gas readings. R values were calculated from the oxygen and carbon dioxide data. Blood samples were immediately analyzed for hematocrit by means of the microhematocrit method in triplicate. The plasma portion of the hematocrit was

then removed and used for lactate analysis with a YSI lactate analyzer. The remainder of the blood was centrifuged, and the plasma was removed and frozen ( - 20° C) for later analysis. Plasma glucose levels were obtained with a commercially available kit (Sigma Diagnostics). Plasma cortisol levels were obtained by a radioimmunoassay technique (Becton Dickinson Immuno Diagnostics). The rest and postexercise plasma cholesterol and triglyceride levels were measured by an autoanalyzer. The data were analyzed by means of analysis of variance techniques comparing each variable for the four trials. When a significant F was obtained, a Tukey a posteriori multiple comparisons test was used to determine the source of the difference. Significance was set at the 0.05 level for all analyses. Results

Postpartum resting oxygen uptake averaged 0.20 ± 0.03 L/min (Table I). This was similar to the 15-week resting Vo 2 , but significantly less than the 25-week or 35-week results. Resting postpartum heart rate averaged 69 ± 3 bpm (Table I). Resting heart rates were significantly elevated by the fifteenth week and remained elevated throughout the duration of pregnancy. Immersion in water to the level of the xiphoid in-

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McMurray et al.

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Table II. Resting blood metabolites and cortisol concentrations with respect to pregnancy status (mean± SEM) 15 weeks Lactate (mmol/L) Glucose (mg/di) Triglyceride (mg/di) Cholesterol (mg/di) Cortisol (µg/dl)

I.I ± 0.2

92.9 132 195 15.2

± ± ± ±

1.5 54 37 3.8

creased the oxygen uptake over resting postpartum values, but no significant effect of pregnancy status was noted (Table I). Immersion heart rates were lower than land rest rates and followed the same trend as the oxygen uptake. Oxygen uptake during the water exercise at 60% of predicted maximal heart rate averaged l.20 ± 0.13 Umin post partum (Table I). The postpartum values were similar to values from the fifteenth and twenty-fifth weeks but greater than those of the thirtyfifth week, which averaged l.12 ± 0.20 Umin. Landpredicted exercise heart rate ranged from 1.45 ± 4 bpm post partum to 151 ± 6 bpm for the thirty-fifth week. No significant difference was noted for the immersion exercise heart rate when compared with pregnancy status. In all patients the exercise heart rates in the water were approximately 15 bpm lower than those in the land trials. Blood lactate values were similar at rest for all trials (Table I). Exercise significantly increased blood lactate, with the highest levels post partum and during the fifteenth weeks compared with either the twentyfifth or thirty-fifth week (Fig. 1). All plasma glucose levels were within normal limits for pregnancy (75 to 95 mg/di), but exercise was found to significantly reduce levels compared with rest (Fig. 1). Resting plasma triglyceride levels were significantly elevated by pregnancy, and there was a tendency for concentrations to increase with duration of pregnancy (Table II). Postexercise values followed the same trend as resting values, with the greatest changes occurring during the twenty-fifth and thirty-fifth weeks (Fig. 1). Plasma cortisol concentrations were not corrected for plasma volume, since changes were <4%. Resting postpartum cortisol levels averaged 5.8 ± 2.9 µg/dl (Table II), which was significantly less than that during pregnancy. Plasma cortisol decreased with immersion and remained low with exercise (Fig. 2). In all patients postpartum levels were lower than during pregnancy, but no significant effect was evident when weeks of pregnancy were compared.

Comment This investigation was designed to explore the effects of immersion and exercise in water. Previous investi-

25 weeks 1.2 89.5 206 247 20.0

0.3 11.8 88 69 ± 4.4

± ± ± ±

35 weeks I.I 85.6 210 215 18.6

± ± ± ± ±

0.3 10.0 IOI 77 3.0

Postpartum 0.8 87.0 102 182 5.8

± ± ± ± ±

0.2 5.1 38 48 2.9

gators have examined only land responses; no data are related to the effects of water. Our land resting data followed the expected trend.1. 9 Metabolism (V 0 2 ) and heart rates increased with the duration of pregnancy. Plasma lactate concentrations were not significantly altered, but glucose concentrations declined, which was probably related to the increased turnover. 1• Resting cortisol levels were three to four times higher than postpartum resting levels as previously documented.' Immersion in 30° C water because of the increase in thermal conductivity presumably placed the subject in negative heat balance. Therefore an elevation in resting metabolic rate would be expected to increase heat production. The increase in metabolic rate over rest was greatest for the fifteenth week (215%) compared with the twenty-fifth week (173%), thirty-fifth week ( 140%), or postpartum ( 155%). The similarity of the immersion metabolic rates for the three pregnancy trials suggests that a specific heat production was necessary to counter the effects of the water. Consequently, the resting metabolic rate increased to meet that demand. Since resting metabolism and therefore heat production increased with advancing pregnancy, the amount of heat necessary to meet the additional demand of the immersion decreased with advancing pregnancy. The metabolic demand during immersion was lower in the postpartum state than during pregnancy. The increased heat production during pregnancy may have been an attempt to maintain an optimal fetal environment caused by the progesterone effect on the thermoregulation center.' Therefore immersion in the 30° C water placed minimal strain on the mother throughout her pregnancy. It should be remembered that normal swimming pool temperatures (25 to 28° C) are somewhat lower than that used in this study. Thus a further increase in metabolic rate and a greater heat loss may be expected, which may result in thermodiscomfort for the women. The work load for predicted 60% work capacities was similar for the fifteenth and twenty-fifth weeks but declined during the thirty-fifth week. Since the work load declined, the absolute oxygen uptake would be expected to decline, which is consistent with our results. Many of the women stated that during the thirty-fifth week trials they could not keep up with the pedaling rate in the water (-50 rpm). This may have been simply

Volume 158 Number 3, Part I

related to abdominal mass-limiting leg cycling. Heart rate responses during the immersion exercise were lower than those predicted from the land exercise but were not significantly altered by pregnancy status. The lower heart rates in the water (compared with land) are in agreement with previous research" and are related to the greater filling of the heart in response to the hydrostatic pressure. Since pregnancy status had minimal effects on oxygen uptake during exercise in the water, substrate use during exercise with respect to duration of pregnancy can be compared. The results indicated that postexercise lactate concentrations decreased at the twentyfifth and thirty-fifth weeks compared with those of the fifteenth week or postpartum. These results are in opposition to the land results previously reported 1. 6 but similar to the recent results of Clapp et al. 15 Theoretically, lactate production may have been significantly changed when corrections are made for the plasma volume expansion known to occur during pregnancy: 9 Postpartum exercise lactate levels were 3.3 mmol/L. By the fifteenth week of pregnancy, plasma volume would be expected to increase by about 25%. Thus fifteenth-week plasma lactate concentration of 3.1 mmol/L would be the same as 3.9 mmol/L for the postpartum plasma volume. Similarly, the 2.4 mmol/L at 25 weeks would be equal to 3.4 mmol/L postpartum (40% plasma volume expansion expected), and 2.5 mmol/L at 35 weeks would be similar to 3.6 mmol/L. Therefore when exercise responses of pregnant and nonpregnant women are compared, exercise during pregnancy probably resulted in no change or a slight increase in total lactate production. Resting blood glucose concentrations, although declining slightly with pregnancy, were within normal limits. Exercise during pregnancy at 60% of predicted capacity caused a significant decrease in blood glucose. This change was not evident in the postpartum state. Artal et al. 6 stated during mild land exercise no change in blood glucose concentration would be expected. The animal research of Chandler et al. 16 agrees. In contrast, Clapp et al. ' 5 and Lotgering et al. 9 point out that it is not uncommon for blood glucose concentrations to decrease during exercise on land, with the decriment more pronounced as exercise intensity increases. Our results suggest that the glucose response to exercise in the water is no different than that expected during land exercise. Artal and Wiswell' have noted that during pregnancy, resting plasma cortisol concentrations increase, particularly during the second half of pregnancy. Our results agree: we noted a threefold rise during the fifteenth week and a fourfold increase during the 25- and 35-week trials. The increase in cortisol may have been responsible for the increase in plasma triglycerides of

Exercise and pregnancy 485

our subjects, since one of the purposes of cortisol is to mobilize lipid stores. Immersion in 30° C water caused a slight but significant decline in cortisol response. Similar responses during cold water immersion have been reported by Rochelle and Horvath," who examined men who had not acclimated to the cold. The decline in cortisol was probably related to the hemodilution that was encountered during the immersion (as indicated by a decrease in hematocrit) or an increase in turnover or excretion rate." An increase in turnover rate would result in greater mobilization of energy reserves to support the increased metabolic rate that occurred during immersion. Plasma cortisol concentrations during exercise were lower than resting levels. Since some hemoconcentration occurred during exercise (see hematocrit data, Table I), an increase in cortisol concentration would have been expected. The low cortisol concentration may have been a result of continued mobilization of energy stores. In support of this hypothesis, we noted that plasma glucose levels declined slightly, but triglycerides were elevated during exercise. Other investigators found no change or increase in cortisol response during exercise. Artal 6 and Rauramo et al. ' 0 found no change in cortisol response, but the exertion was extremely mild compared with ours. The study reported by Lotgering et al. 9 involved strenuous exercise in pregnant sheep. Thus considerable differences existed between these studies and ours. Previous studies have used R values to indicate exercise substrate use.'· 5 · 7 These studies have concluded that exercise in pregnant women is completed at considerable carbohydrate expense. We believe that caution is necessary when interpreting R value results. R values are the ratio of carbon dioxide output to oxygen uptake. Several studies,'· 4 including ours, have found a hyperventilatory response in pregnant women both at rest and during exercise. This response would cause a greater carbon dioxide output resulting in an inflated R value, which would be interpreted as greater carbohydrate use. Therefore one must examine other metabolic markers to determine substrate use correctly during exercise. Our observations of a slight decline in blood glucose and an increase in total lactate production suggest that in the pregnant state considerably more glucose is used as an energy source for exercise. Although glucose decreased, the increase in triglycerides cannot be overlooked. Indeed, if cortisol turnover increased, then the suggestion is that the triglycerides were sequestered by the liver to replenish glucose levels. Thus, despite the inflated R value, our results suggest that at a moderate level of exertion in the water, carbohydrate stores are the primary source of energy. This is in agreement with previously published data for land exercise.

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Am .J Obstet Gynecol

Our results suggest that immersion and moderate exercise in water do not result in any metabolic compromise. Although changes in blood glucose, lactate, triglycerides, and cortisol concentrations are evident, they present no detrimental effect to pregnant women. Our water temperatures were slightly greater than one would expect for a swimming pool, and cooler water temperatures may magnify some of the metabolic changes. We would not expect any metabolic compromise during swimming since the heat production from the exercise counters the heat loss. Conversely, prolonged immersion in cool swimming pools without exercise may result in considerable heat loss, and we would expect to see further elevation of metabolic rate and possible signs of thermodiscomfort.

6. 7. 8. 9. 10. 11. 12.

REFERENCES I. Artal R, Wiswell R. Exercise in pregnancy. Baltimore: Williams & Wilkins, 1986: 1-228. 2. Katz J. Swimming through your pregnancy, the perfect exercise for pregnant women. New York: Doubleday, 1983:1-159. 3. Knuttgen HG, Emerson Jr K. Physiological responses to pregnancy at rest and during exercise. J Appl Physiol I 974;36:549-53. 4. Pernoll ML, Metcalfe J, Kovach PA, Wachtel R, Dunham MJ. Ventilation during rest and exercise in pregnancy and postpartum. Respir Physiol l 975;25:295-310. 5. Seitchik J. Body composition and energy expenditure

13.

14. 15. 16.

during rest and work in pregnancy. AM J OBSTET GvNECOL 1967;97:701-13. Artal R, Platt LD, Sperling M, Kammula RK,Jilekj, Nakamura R. Exercise in pregnancy. AM J 0BSTET GYNECOL 1981; 140: 123-7. Blackburn MW, Calloway DH. Basal metabolic rate and work energy expenditure of mature, pregnant women. J Am Diet Assoc 1976;69:24-8. Gorski J. Energy sources mobilization during muscular exercise in pregnant rats. Acta Physiol Pol 1983;34: 269-76. Lotgering FK, Gilbert RD, Longo LD. Maternal and fetal responses to exercise during pregnancy. Physiol Rev 1985;65: 1-36. Rauramo I, Andersson B, Laatikainen T. Stress hormones and placental steroids in physical exercise during pregnancy. Br J Obstet Gynaecol I 982;89:921-5. Rochelle RD, Horvath SM. Thermoregulation in surfers and nonsurfers immersed in cold water. Undersea Biomed Res 1978;5:377-90. Morlock JF, Dressendorfer RH. Modification of a standard bicycle ergometer for undersea use. Undersea Biomed Res 1974;1:335-42. Risch WD, Koubenee H, Bechmann U, Lange S, Gauer OH. The effect of graded immersion on heart volume, central venous pressure, pulmonary blood distribution, and heart in man. Pflugers Arch 1978;374: 115-8. Knopp RH. Fuel metabolism in pregnancy. Contemp Obstet Gynecol 1978; 12:83-90. Clapp JF, Wesley M, Sleamaker RH. Thermoregulatory and metabolic responses to jogging prior to and during pregnancy. Med Sci Sports Exerc 1987;19:124-30. Chandler KD, Bell AW. Effects of materna.l exercise on fetal and maternal respiration and nutrient metabolism in the pregnant ewe. J Dev Physiol 1981;3:161-76.

The effect of hepatitis B antigenemia on pregnancy outcome Joseph G. Pastorek II, MD, Joseph M. Miller, Jr., MD, and Paul R. Summers, MD New Orleans, Louisiana Sixty patients documented to have hepatitis B antigenemia during pregnancy were identified retrospectively and compared with an equal number of matched control patients. Maternal and newborn infant parameters were examined. No statistically significant differences were noted between the two groups, except for an increase in infant birth weight in the group showing antigen-positive test results, specifically in infants born to Oriental mothers. It is concluded that infants born to women testing positive for hepatitis B surface antigen represent normal infants eminently suitable for peripartal preventive immunotherapy. (AM J 0BSTET GYNECOL 1988;158:486-9.)

Key words: Hepatitis B surface antigen, pregnancy, pregnancy outcome Neonates born to mothers testing positive for hepatitis B surface antigen are at risk for vertical receipt

From the Departments of Obstetrics and Gynecology, Louisiana State University Medical Center and Tulane University School of Medu:me. Received for publication July 2, 1987; revised August 26, 1987; accepted September 22, 1987. Reprint requests: Dr.Joseph G. Pastorek II., LSUMC, 1542 Tulane Ave., New Orleans, LA 70112.

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of the virus, with subsequent development of antigenemia, hepatitis, cirrhosis, and even hepatocellular carcinoma. In areas of high prevalence such as the Orient, as many as 40% of hepatitis B cases may be the result of perinatal vertical transmission of the virus,' which makes perinatal vertical transmission of the disease one of the most important modes of transmission of the disease worldwide. The fact that perinatal transmission of hepatitis B