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Correlation between urinary estriol excretion and fetal acidosis in high-risk pregnancies
Correlation between urinary estriol excretion and fetal acidosis in high-risk pregnancies J.
H.
FLIEGNER,
M.B.,
F.R.A.C.S., PETER
N.
A.
J.
M.B.,
WOOD,
B.
BROWN,
Melbourne,
Victoria,
B.S.,
M.B.,
BEISCHER,
F.R.A.C.S.,
(E~rri.),
M.R.C.O.C.
RENOU,
CARL
F.R.C.S.
M.R.C.O.G.
F.R.C.S., M.B.,
F.R.C.O.G. M.G.O.,
F.R.A.C.S.
(EDIN.),
M.R.C.O.G. M.Sc.(N.Z.),
PH.D.(EDIN.)
Australia
Urinary estriol
excretion and fetal acid-base status were measured in 80 patients with high-risk pregnancies. Estriol excretion was below normal limits in 24 patients (30 per cent), and in this group the incidence of pH values less than 7.20 was 41 per cent, which was significantly different from that in patients with normalestriol values (p < 0.001). The detection of low urinary estriol excretion by screening of all high-risk pregnancies would enable more accurate selection ,of those patients who require fetal blood pH measurement.
TH E
N E E D for more accurate diagnosis
exists as clinical methods are inadequate in selecting all patients in whom the fetus is in jeopardy. Extensive studies of the measurement of urinary excretion of estriol have shown this to be useful in predicting fetal hazard. In patients with pre-eclampsia, hypertension, and suspected placental insufficiency the estriol excretion is invariably below normal when perinatal deaths occur.4 In the present investigation both the urinary excretion of estriol and the fetal acidbasestatus were measuredin 80 patients and these results analyzed in relation to the fetal outcome. By this means it was hoped to compare the usefulnessof these 2 tests of fetal condition and to determine whether the measurement of urinary estriol excretion would enable more .accurate selection of patients requiring fetal blood pH measurement.
of fetal distress is emphasisedby the poor correlation between the condition of the infant at birth and that predicted by the clinical criteria of alteration of fetal heart rate and the presence of meconium in the 1iquor.l Recently it has been shown that the measurement of pH in fetal scalp blood during labor is more accurate in determining fetal prognosis than are the clinical signs of fetal distress.2Only 1 in 5 patients with meconium in the liquor has a low fetal pH been found and those patients with a normal fetal pH can be managed conservativel~.~ While fetal pH may improve diagnostic accuracy for the obstetrician, a problem concerning the selection of patients for this test From the Departments of Obstetrics and Gynaecology, University of Melbourne, Royal Women’s Hospital, and Monash University Medical School, and Queen Victoria Memorial Hospital. This
study
was sup
orted
Material
methods
Table I lists the main obstetric eomplications indicating investigation, but most patients showed evidence of intrauterine growth
by grants
from the National R e&h and Medical Research Council and The Three R’s Research
and
Foundation.
252
Volume Number
High-risk
105 2
pregnancies
253
Table I. Indications for investigation of urinary estriol and fetal acid-base status and associated obstetric data
Indication investigation
No. of patients
for
Prolonged pregnancy (3 42 weeks) Intrauterine growth retardation Hypertension Pre-eclampsia with proteinuria Rhesus isoimmunization Diabetes mellitus
Subnormal estriol values
Meconium in liquor
Apgar o-3
11
3
3
7
1
1
2
21 23
8 2
4 1
7 6
3 1
3 2
8 4
21
10
5
6
5
7
1
1 1
-
-
28
5
11
1 i
Total
No liquor
Fetal growth retardation (weight
80
24
14
I 22
Table II. ReIationship between urinary estriol excretion, fetal pH, and the condition of the fetus at birth Fetal Urinary estriol values
Fetal
No. of patients
< 7.20
pH
Apgar
1 > 7.20
Normal Subnormal
56 24
4(7%) 10 (41%)”
52 14
Total
80
41
66
*The incidence of low pH in the patients with subnormal normal estriol values (p < 0.001). tThe incidence of fetal growth retardation in the patients in patients with normal estriol levels (p < 0.001).
o-3
score 1
5 ( 9%) 6 (25%) 11 estriol
levels
with
subnormal
is
growth
4.10
weight < IOth bercentile
51 18
8 (14%) 14 (58%)t
69
22
significantly
different
retardation > 10th percentile 48 10 58
from
that
in
patients
with
retardation, although this was seldom the only abnormality present. This study was performed during the 12 months January to December, 1967, and the patients were selected from the combined obstetrics populations of the Royal Women’s Hospital and the Queen Victoria Memorial Hospital, Mdbourne, an annual total of approximately 13,000 patients. Estriol excretion was measured by the method of Brown and associates5and was considered to be subnormal if the values were below the line joining 8 mg. at 30 weeks’ gestation to 12 mg. at 40 weeks and beyond.* Fetal scalp capillary blood was collected by the method of Saling.B The fetal pH was measured by the ultramicromethod of Astrup and associates7or an I. L. 113 ultramicroelectrode assembly at 38O
estriol
values
is significantly
different
from
that
C. The condition of the infant at birth was assessed by the Apgar score 2 minutes after delivery and the presence or absence of pIacenta1 insufficiency, evaluated by a senior pediatrician. Fetal growth retardation was diagnosed when the infant’s weight was below the tenth percentile for the period of gestation as seen in patients in this community.8 Results
Normal excretion of urinary estriol (Table II). Only 4 of 56 patients in this group had a fetal blood pH of less than 7.20. This incidence of low pH is similar to that of patients with “high-risk” pregnancies.3Of the 4 with a low pH, 3 were born in poor condition (Apgar O-3) but soon recovered and in the other a repeat pH measurement
254
Fliegner
et al.
was normal (Case 5). Both the urinary estriol and fetal blood pH were normal in 2 patients whose fetuses were born with a low Apgar score. In one of them the cord prolapsed some time after the fetal blood collection and the fetus was stillborn, while the other developed an abnormal heart rate pattern 1 to 2 hours before delivery. In these 56 patients with normal estriol excretion the incidence of cesarean section was 12.5 per cent and the perinatal mortality rate was 1.8 per cent. Subnormal excretion of urinary estriol (Table II). Low estriol values were recorded in 30 per cent of the 80 patients, which is a similar incidence to that previously reported in complicated pregnancies4 Fortyone per cent of the patients with low estrio1 values had a fetal scalp blood pH of less than 7.20, and this incidence was significantly higher (p
case
reports
The value of low urinary estriol excretion and low fetal pH as joint indicators of significant and perhaps irreversible fetal damage is shown in Cases 1 to 3. There seems no place for conservative management when both of these parameters indi-
cate fetal jeopardy, irrespective of the fetal heart rate pattern. Case1. Clinical evidence of intrauterine fetal growth retardation was first noted at 32 weeks’ gestation in a 27-year-old primigravida with hypertension. Urinary estriol excretion was 17 mg. per 24 hours at 32 weeksbut had fallen to 4.9 mg. at 35 weeks,at which time proteinuria was first recorded. At amniotomy at 36 weeks’ gestationthe liquor was clear, but the fetal pH was 7.13 and after 6 hours a value of 6.79 was obtained. The fetal heart rate was monitored and showedchanges,suggestinguteropIacenta1 insufficiency. Fetal heart soundsbecameunrecordable20 minuteslater. The infant wasa stillborn male and weighed 1,050 grams.The placenta weighed 325 grams and showedextensive infarction. Case2. A 23-year-old primigravida with clinical evidence of oligohydramnioshad a urinary estriol excretion of 7.2 mg. at 43 weeks’gestation. No liquor was obtained at amniotomy but, as the fetal heart wasregular, labor wasallowed to proceed. The fetal pH when the cervix was 4 cm. diIated was 7.14. After 12 hours of labor the patient was spontaneouslydelivered of a female infant weighing 2,970grams.The infant showedobvious placental insufficiency, required vigorous resuscitation,and had 4 cyanotic attacks during the 36 hours after birth. The placenta weighed 400 grams. Case 3. A 25-year-old primigravida had a urinary estriol excretion of 9.8 mg. at 42 weeks’ gestation.Meconium-stainedliquor was obtained at amniocentesis and amniotomy and, following the latter procedure,the fetal heart was irregu lar, Auctuating between 90 and 100 beats per minute. The fetal scalp pH at amniotomy was 7.14. Cesareansection was performed and the patient was delivered of a male infant weighing 2,540 grams. The infant was in poor condition at birth and although resuscitationwas effective, there were subsequentlya number of cyanotic attacks. The placentaweighed350 grams. Although low estriol excretion indicates termination of a mature pregnancy, a fetal pH within the normal range shows that there is no need for immediate abdominal delivery. The patient in the foIlowing report had an estriol value which is usually diagnostic of intrauterine fetal death yet at birth the condition of the infant was satisfactory.
Volume 105 Number 2
Case 4. A 20-year-old primigravida with clinical evidence of intrauterine fetal growth retardation had a urinary estriol excretion of 0.9. mg. at 41 weeks’ gestation. An amniotomy meconium was obtained and the fetal scalp pH was 7.29. The fetal delivery was performed. The infant, a living female weighing 2,620 grams, showed the signs of growth retardation but had an Apgar score of 7 at 2 minutes. Atelectasis was the only neonatal complication. The placenta weighed 650 grams and contained several infarcts. The finding of fetal acidosis determines the time and therefore the method of delivery, but its presence should be confirmed by a second estimation of scalp blood PH. The next case report illustrates the need for this as an initial low pH was not confirmed on the second fetal blood pH measurement. Case 5. A 21-year-old primigravida with hypertension had an amniotomy performed at 38 weeks’ gestation, the estriol values having been 29 mg. both at 36 and 37 weeks. The amniotic fluid contained meconium and the scalp pH was 7.18. The fetal heart rate was normal. Repetition of pH estimation gave a value of 7.38. Spontaneous labor was ahowed and a living male infant weighing 3,070 grams was born in good condition by midforceps delivery. The placenta weighed 525 grams. Comment
From the present study it was clear that a low urinary excretion can be used not only to help determine the timing of termination of a pregnancy but also to predict the likelihood of the presence of fetal acidosis. As indicated in the case reports, both the tests have somelimitation, but when used in combination they have an increased value to the obstetrician, A number of studies have demonstrated a relationship between fetal acidosisand the condition of the fetus at birth.2p 6p0slo This relationship will depend partly upon whether the newborn infant is depressed by complications present before or during labor or occurring at the time of birth due to the mechanics of delivery. In our previous studies of fetal pH during the first stage of labor, a large number of chronic com-
High-risk pregnancies
255
plications, such as pre-eclampsia, hypertension, and growth retardation, were present, and this probably accounted for our positive correlation between fetal pH and the Apgar score. In an obstetric population without any natal complications, such correlation would not be expected, as the main factors depressing the fetus, such as anesthesia, midforceps delivery, or shoulder dystocia, would occur after the time of fetal blood collection. Paul, Gare, and Whethami found only 2 of 146 fetuses with a pH less than 7.20 in the first stage of labor, and this could be partly accounted for by their selection of patients without serious obstetric complications. At the present time we would advocate the screening of all high-risk pregnancies by measurement of the urinary excretion of estriol. Patients with low levels or showing clinical deterioration should have this repeated at intervals. From the results of this test and the clinical findings, the need for termination of the pregnancy and its timing can be determined. If the urinary estriol is low or meconium is present in the liquor at the time of membrane rupture, then the fetal scalp blood pH should be measured. Maternal blood pH is also measured, as maternal acidosis may cause fetal acidosis. Further studies will be necessary before an authoritative statement can be made on how to use these 2 fetal diagnostic tests in the management of labor. However, from our previous experience of measurement of fetal scalp blood pH in 250 patients during labor2 and the results of the present investigation, the following pIan of management is suggested. If the fetal pH is less than 7.15 on 2 separate measurements, even if estriol excretion is normal, cesarean section is indicated unless conditions are suitable for immediate vaginal delivery. When estriol excretion is below normal, a fetal scalp pH of less than 7.20 is regarded as sufficient additional indication to warrant elective cesarean section, irrespective of the presence of clinical signs of fetal distress (Cases 1 to 3). The management of patients must take into consideration clinical features as well
256
Fliegner
et al.
as the results of investigations, but it is thought that the combination of urinary estriol excretion and fetal blood pH measurements has added another safeguard to obstetrics. The present study is also relevant to the understanding of fetoplacental function, as it is apparent that when estriol production is decreased in the fetoplacental unit, then fetal blood pH is also likely to change. Fetal acidosis and failure of estriol synthesis may both be caused by asphyxia, although other mechanisms cannot be excluded. It is possible that low fetal pH values before the onset of labor may be found only in patients
REFERENCES
1. Wood, C., and Pinkerton, J. H. M.: J. Obst. & Gynaec. Brit. Comm. 68: 427, 1961. 2. Wood, C.: In Prenatal Life, Biological and Clinical Perspectives, Springfield, Illinois, 1968, Charles C Thomas, Publisher. 3. Wood, C., Ferguson, R., Leeton, J., Newman, W., and Walker, A.: AM. J. OBST. & GYNEC. 98: 62, 1967. 4. MacLeod, S. Cl., Brown, J. B., Beischer, N. A., and Smith, M. A.: Australia-New Zealand J. Obst. & Gynaec. 1: 25, 1967. 5. Brown, J. B., MacLeod, S. C., Macnaughtan, C., Smith, M. A., and Smyth, B.: J. Endocrinol. In press, 1968, 6. Saling, E. J.: Internat. Fed. Gynaec. & Obst. 3: 101, 1965. 7. Astrup, P., Jorgensen, K., Siggard Anderson, O., and Engel, K.: Lancet 1: 1035, 1960.
with long-standing subnormal urinary estriol excretion, and it is such patients whose infants may be found on follow-up examination to be mentally retarded.l”z I3 When fetal acid-base status becomes abnormal only as a result of the stress of labor, prompt delivery, when effected without birth trauma, should be associated with more favorable perinatal mortality and morbidity rates. We are grateful to the Medical Staffs of our Hospitals for their cooperation in this study. Dr. Warwick Newman, Misses Judith Hammond, and Margery Smith provided skilled technical assistance.
8. Kitchen, W. H.: Australian Paediat. J. In press, 1968. 9. Mender-Bauer, C., Arnt, I. C., Escarcena, L., and Caldeyro-Barcia, R.: AM. J. OBST. & GYNEC. 97: 530, 1967. 10. Beard, R. W., Morris, E. D., and Clayton, S. G.: J. Obst. & Gynaec. Brit. Comm. 73: 562, 1966. 11. Paul, W. M., Gare, D. J., and Whetham, J. C.: AM. J. OBST. & GYNEC. !#: 745, 1967. 12. Wallace, S. J., and Michie, E. A.: Lancet 2: 560, 1966. 13. Brown, J. B., and Beischer, N. A.: In Wood, C.. and Walters. W. A. W.. editors: Fifth World Congress’ of Gynaecology and Obstetrics, Sydney, Australia, Butterworth & Company, Ltd., p. 75.
H.
FLIEGNER,
M.B.,
F.R.A.C.S., PETER
N.
A.
J.
M.B.,
WOOD,
B.
BROWN,
Melbourne,
Victoria,
B.S.,
M.B.,
BEISCHER,
F.R.A.C.S.,
(E~rri.),
M.R.C.O.C.
RENOU,
CARL
F.R.C.S.
M.R.C.O.G.
F.R.C.S., M.B.,
F.R.C.O.G. M.G.O.,
F.R.A.C.S.
(EDIN.),
M.R.C.O.G. M.Sc.(N.Z.),
PH.D.(EDIN.)
Australia
Urinary estriol
excretion and fetal acid-base status were measured in 80 patients with high-risk pregnancies. Estriol excretion was below normal limits in 24 patients (30 per cent), and in this group the incidence of pH values less than 7.20 was 41 per cent, which was significantly different from that in patients with normalestriol values (p < 0.001). The detection of low urinary estriol excretion by screening of all high-risk pregnancies would enable more accurate selection ,of those patients who require fetal blood pH measurement.
TH E
N E E D for more accurate diagnosis
exists as clinical methods are inadequate in selecting all patients in whom the fetus is in jeopardy. Extensive studies of the measurement of urinary excretion of estriol have shown this to be useful in predicting fetal hazard. In patients with pre-eclampsia, hypertension, and suspected placental insufficiency the estriol excretion is invariably below normal when perinatal deaths occur.4 In the present investigation both the urinary excretion of estriol and the fetal acidbasestatus were measuredin 80 patients and these results analyzed in relation to the fetal outcome. By this means it was hoped to compare the usefulnessof these 2 tests of fetal condition and to determine whether the measurement of urinary estriol excretion would enable more .accurate selection of patients requiring fetal blood pH measurement.
of fetal distress is emphasisedby the poor correlation between the condition of the infant at birth and that predicted by the clinical criteria of alteration of fetal heart rate and the presence of meconium in the 1iquor.l Recently it has been shown that the measurement of pH in fetal scalp blood during labor is more accurate in determining fetal prognosis than are the clinical signs of fetal distress.2Only 1 in 5 patients with meconium in the liquor has a low fetal pH been found and those patients with a normal fetal pH can be managed conservativel~.~ While fetal pH may improve diagnostic accuracy for the obstetrician, a problem concerning the selection of patients for this test From the Departments of Obstetrics and Gynaecology, University of Melbourne, Royal Women’s Hospital, and Monash University Medical School, and Queen Victoria Memorial Hospital. This
study
was sup
orted
Material
methods
Table I lists the main obstetric eomplications indicating investigation, but most patients showed evidence of intrauterine growth
by grants
from the National R e&h and Medical Research Council and The Three R’s Research
and
Foundation.
252
Volume Number
High-risk
105 2
pregnancies
253
Table I. Indications for investigation of urinary estriol and fetal acid-base status and associated obstetric data
Indication investigation
No. of patients
for
Prolonged pregnancy (3 42 weeks) Intrauterine growth retardation Hypertension Pre-eclampsia with proteinuria Rhesus isoimmunization Diabetes mellitus
Subnormal estriol values
Meconium in liquor
Apgar o-3
11
3
3
7
1
1
2
21 23
8 2
4 1
7 6
3 1
3 2
8 4
21
10
5
6
5
7
1
1 1
-
-
28
5
11
1 i
Total
No liquor
Fetal growth retardation (weight
80
24
14
I 22
Table II. ReIationship between urinary estriol excretion, fetal pH, and the condition of the fetus at birth Fetal Urinary estriol values
Fetal
No. of patients
< 7.20
pH
Apgar
1 > 7.20
Normal Subnormal
56 24
4(7%) 10 (41%)”
52 14
Total
80
41
66
*The incidence of low pH in the patients with subnormal normal estriol values (p < 0.001). tThe incidence of fetal growth retardation in the patients in patients with normal estriol levels (p < 0.001).
o-3
score 1
5 ( 9%) 6 (25%) 11 estriol
levels
with
subnormal
is
growth
4.10
weight < IOth bercentile
51 18
8 (14%) 14 (58%)t
69
22
significantly
different
retardation > 10th percentile 48 10 58
from
that
in
patients
with
retardation, although this was seldom the only abnormality present. This study was performed during the 12 months January to December, 1967, and the patients were selected from the combined obstetrics populations of the Royal Women’s Hospital and the Queen Victoria Memorial Hospital, Mdbourne, an annual total of approximately 13,000 patients. Estriol excretion was measured by the method of Brown and associates5and was considered to be subnormal if the values were below the line joining 8 mg. at 30 weeks’ gestation to 12 mg. at 40 weeks and beyond.* Fetal scalp capillary blood was collected by the method of Saling.B The fetal pH was measured by the ultramicromethod of Astrup and associates7or an I. L. 113 ultramicroelectrode assembly at 38O
estriol
values
is significantly
different
from
that
C. The condition of the infant at birth was assessed by the Apgar score 2 minutes after delivery and the presence or absence of pIacenta1 insufficiency, evaluated by a senior pediatrician. Fetal growth retardation was diagnosed when the infant’s weight was below the tenth percentile for the period of gestation as seen in patients in this community.8 Results
Normal excretion of urinary estriol (Table II). Only 4 of 56 patients in this group had a fetal blood pH of less than 7.20. This incidence of low pH is similar to that of patients with “high-risk” pregnancies.3Of the 4 with a low pH, 3 were born in poor condition (Apgar O-3) but soon recovered and in the other a repeat pH measurement
254
Fliegner
et al.
was normal (Case 5). Both the urinary estriol and fetal blood pH were normal in 2 patients whose fetuses were born with a low Apgar score. In one of them the cord prolapsed some time after the fetal blood collection and the fetus was stillborn, while the other developed an abnormal heart rate pattern 1 to 2 hours before delivery. In these 56 patients with normal estriol excretion the incidence of cesarean section was 12.5 per cent and the perinatal mortality rate was 1.8 per cent. Subnormal excretion of urinary estriol (Table II). Low estriol values were recorded in 30 per cent of the 80 patients, which is a similar incidence to that previously reported in complicated pregnancies4 Fortyone per cent of the patients with low estrio1 values had a fetal scalp blood pH of less than 7.20, and this incidence was significantly higher (p
case
reports
The value of low urinary estriol excretion and low fetal pH as joint indicators of significant and perhaps irreversible fetal damage is shown in Cases 1 to 3. There seems no place for conservative management when both of these parameters indi-
cate fetal jeopardy, irrespective of the fetal heart rate pattern. Case1. Clinical evidence of intrauterine fetal growth retardation was first noted at 32 weeks’ gestation in a 27-year-old primigravida with hypertension. Urinary estriol excretion was 17 mg. per 24 hours at 32 weeksbut had fallen to 4.9 mg. at 35 weeks,at which time proteinuria was first recorded. At amniotomy at 36 weeks’ gestationthe liquor was clear, but the fetal pH was 7.13 and after 6 hours a value of 6.79 was obtained. The fetal heart rate was monitored and showedchanges,suggestinguteropIacenta1 insufficiency. Fetal heart soundsbecameunrecordable20 minuteslater. The infant wasa stillborn male and weighed 1,050 grams.The placenta weighed 325 grams and showedextensive infarction. Case2. A 23-year-old primigravida with clinical evidence of oligohydramnioshad a urinary estriol excretion of 7.2 mg. at 43 weeks’gestation. No liquor was obtained at amniotomy but, as the fetal heart wasregular, labor wasallowed to proceed. The fetal pH when the cervix was 4 cm. diIated was 7.14. After 12 hours of labor the patient was spontaneouslydelivered of a female infant weighing 2,970grams.The infant showedobvious placental insufficiency, required vigorous resuscitation,and had 4 cyanotic attacks during the 36 hours after birth. The placenta weighed 400 grams. Case 3. A 25-year-old primigravida had a urinary estriol excretion of 9.8 mg. at 42 weeks’ gestation.Meconium-stainedliquor was obtained at amniocentesis and amniotomy and, following the latter procedure,the fetal heart was irregu lar, Auctuating between 90 and 100 beats per minute. The fetal scalp pH at amniotomy was 7.14. Cesareansection was performed and the patient was delivered of a male infant weighing 2,540 grams. The infant was in poor condition at birth and although resuscitationwas effective, there were subsequentlya number of cyanotic attacks. The placentaweighed350 grams. Although low estriol excretion indicates termination of a mature pregnancy, a fetal pH within the normal range shows that there is no need for immediate abdominal delivery. The patient in the foIlowing report had an estriol value which is usually diagnostic of intrauterine fetal death yet at birth the condition of the infant was satisfactory.
Volume 105 Number 2
Case 4. A 20-year-old primigravida with clinical evidence of intrauterine fetal growth retardation had a urinary estriol excretion of 0.9. mg. at 41 weeks’ gestation. An amniotomy meconium was obtained and the fetal scalp pH was 7.29. The fetal delivery was performed. The infant, a living female weighing 2,620 grams, showed the signs of growth retardation but had an Apgar score of 7 at 2 minutes. Atelectasis was the only neonatal complication. The placenta weighed 650 grams and contained several infarcts. The finding of fetal acidosis determines the time and therefore the method of delivery, but its presence should be confirmed by a second estimation of scalp blood PH. The next case report illustrates the need for this as an initial low pH was not confirmed on the second fetal blood pH measurement. Case 5. A 21-year-old primigravida with hypertension had an amniotomy performed at 38 weeks’ gestation, the estriol values having been 29 mg. both at 36 and 37 weeks. The amniotic fluid contained meconium and the scalp pH was 7.18. The fetal heart rate was normal. Repetition of pH estimation gave a value of 7.38. Spontaneous labor was ahowed and a living male infant weighing 3,070 grams was born in good condition by midforceps delivery. The placenta weighed 525 grams. Comment
From the present study it was clear that a low urinary excretion can be used not only to help determine the timing of termination of a pregnancy but also to predict the likelihood of the presence of fetal acidosis. As indicated in the case reports, both the tests have somelimitation, but when used in combination they have an increased value to the obstetrician, A number of studies have demonstrated a relationship between fetal acidosisand the condition of the fetus at birth.2p 6p0slo This relationship will depend partly upon whether the newborn infant is depressed by complications present before or during labor or occurring at the time of birth due to the mechanics of delivery. In our previous studies of fetal pH during the first stage of labor, a large number of chronic com-
High-risk pregnancies
255
plications, such as pre-eclampsia, hypertension, and growth retardation, were present, and this probably accounted for our positive correlation between fetal pH and the Apgar score. In an obstetric population without any natal complications, such correlation would not be expected, as the main factors depressing the fetus, such as anesthesia, midforceps delivery, or shoulder dystocia, would occur after the time of fetal blood collection. Paul, Gare, and Whethami found only 2 of 146 fetuses with a pH less than 7.20 in the first stage of labor, and this could be partly accounted for by their selection of patients without serious obstetric complications. At the present time we would advocate the screening of all high-risk pregnancies by measurement of the urinary excretion of estriol. Patients with low levels or showing clinical deterioration should have this repeated at intervals. From the results of this test and the clinical findings, the need for termination of the pregnancy and its timing can be determined. If the urinary estriol is low or meconium is present in the liquor at the time of membrane rupture, then the fetal scalp blood pH should be measured. Maternal blood pH is also measured, as maternal acidosis may cause fetal acidosis. Further studies will be necessary before an authoritative statement can be made on how to use these 2 fetal diagnostic tests in the management of labor. However, from our previous experience of measurement of fetal scalp blood pH in 250 patients during labor2 and the results of the present investigation, the following pIan of management is suggested. If the fetal pH is less than 7.15 on 2 separate measurements, even if estriol excretion is normal, cesarean section is indicated unless conditions are suitable for immediate vaginal delivery. When estriol excretion is below normal, a fetal scalp pH of less than 7.20 is regarded as sufficient additional indication to warrant elective cesarean section, irrespective of the presence of clinical signs of fetal distress (Cases 1 to 3). The management of patients must take into consideration clinical features as well
256
Fliegner
et al.
as the results of investigations, but it is thought that the combination of urinary estriol excretion and fetal blood pH measurements has added another safeguard to obstetrics. The present study is also relevant to the understanding of fetoplacental function, as it is apparent that when estriol production is decreased in the fetoplacental unit, then fetal blood pH is also likely to change. Fetal acidosis and failure of estriol synthesis may both be caused by asphyxia, although other mechanisms cannot be excluded. It is possible that low fetal pH values before the onset of labor may be found only in patients
REFERENCES
1. Wood, C., and Pinkerton, J. H. M.: J. Obst. & Gynaec. Brit. Comm. 68: 427, 1961. 2. Wood, C.: In Prenatal Life, Biological and Clinical Perspectives, Springfield, Illinois, 1968, Charles C Thomas, Publisher. 3. Wood, C., Ferguson, R., Leeton, J., Newman, W., and Walker, A.: AM. J. OBST. & GYNEC. 98: 62, 1967. 4. MacLeod, S. Cl., Brown, J. B., Beischer, N. A., and Smith, M. A.: Australia-New Zealand J. Obst. & Gynaec. 1: 25, 1967. 5. Brown, J. B., MacLeod, S. C., Macnaughtan, C., Smith, M. A., and Smyth, B.: J. Endocrinol. In press, 1968, 6. Saling, E. J.: Internat. Fed. Gynaec. & Obst. 3: 101, 1965. 7. Astrup, P., Jorgensen, K., Siggard Anderson, O., and Engel, K.: Lancet 1: 1035, 1960.
with long-standing subnormal urinary estriol excretion, and it is such patients whose infants may be found on follow-up examination to be mentally retarded.l”z I3 When fetal acid-base status becomes abnormal only as a result of the stress of labor, prompt delivery, when effected without birth trauma, should be associated with more favorable perinatal mortality and morbidity rates. We are grateful to the Medical Staffs of our Hospitals for their cooperation in this study. Dr. Warwick Newman, Misses Judith Hammond, and Margery Smith provided skilled technical assistance.
8. Kitchen, W. H.: Australian Paediat. J. In press, 1968. 9. Mender-Bauer, C., Arnt, I. C., Escarcena, L., and Caldeyro-Barcia, R.: AM. J. OBST. & GYNEC. 97: 530, 1967. 10. Beard, R. W., Morris, E. D., and Clayton, S. G.: J. Obst. & Gynaec. Brit. Comm. 73: 562, 1966. 11. Paul, W. M., Gare, D. J., and Whetham, J. C.: AM. J. OBST. & GYNEC. !#: 745, 1967. 12. Wallace, S. J., and Michie, E. A.: Lancet 2: 560, 1966. 13. Brown, J. B., and Beischer, N. A.: In Wood, C.. and Walters. W. A. W.. editors: Fifth World Congress’ of Gynaecology and Obstetrics, Sydney, Australia, Butterworth & Company, Ltd., p. 75.