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Induction of labor
Induction of labor Readiness for induction
HARRY Philadelphia,
FIELDS,
M.D.
Pennsylvania
METHODS TO PREDICT the onset of labor or pinpoint the end of full-term pregnancy have been for the most part inaccurate. Menstrual history, various abdominal measurements, evaluation of the uterine cervix, uterine irritability, and even x-ray examination have been used with little consistent success. Although the cervix is a good indicator of the ease with which a patient may be induced, it is common knowledge that many patients with soft, dilated cervices may carry pregnancies for a month or more without spontaneous labor. If such patients are electively induced on the basis of the “ripeness” of the cervix alone, prematurity of the infant is common, with all the inherent dangers of morbidity and mortality. Since the ripeness of the cervix is not always a good indicator, other means of determining the readiness of a patient for induction must be considered. In a study of induction of labor at the Hospital of the University of Pennsylvania, from 1950 to date, observations have revealed that there are features, other than the condition of the cervix, which should influence the decision as to when to induce a patient. The factors used to determine the readiness for induction are as follows: ( 1) calculated date of confinement, (2) patient attitude, (3) estimated size of the infant, (4) uterine irrita-
bility, (5) softness of the ment, (7) position of the of the presenting part, (10) recent increase in
cervix, (6) effacecervix, (8) station (9) dilatation, and vaginal discharge.
Method of scoring Each one of these factors may be scored as 0, 1, or 2, yielding a maximum score of 20. The combined total represents the patient’s readiness for induction. Calculated date of confinement. If the patient gives a poor menstrual history and the expected date of confinement is uncertain, or she is more than 3 weeks prior to that date, this factor is scored 0. If the history is accurate, the patient is more than one week and less than 3 weeks prior to the estimated date of confinement, she receives a score of 1, and within one week of the estimated date of confinement or after it, the score is 2. Patient’s attitude. If the patient objects to or fears induction of labor, she is scored 0; if she hesitates but accepts elective induction of labor after it is explained to her, 1; and if she requests induction or is enthusiastic about it, she receives a score of 2. Estimated size of the infant. When the infant is considered less than 2,500 grams, the score is 0. If there is some question as to the size of the infant, the score is 1. If the infant is definitely estimated to be well over 2,500 grams, a score of 2 is given. Uterine irritability. Manual abdominal palpation may produce uterine contractions. If the uterus is flaccid following abdominal palpation, this factor is scored as 0. If a certain amount of tension develops as a
From the Department of Obstetrics and Gynecology, School of Medicine, University of Pennsylvania. Read in #art before the Obstetrical Society of Philadelphia, Nov. 7, 1963.
426
Volume Number
95 3
Induction
result of abdominal palpation, it is scored as 1. When the uterus develops a full, firm contraction in response to palpation, it is scored as 2. Softness of the cervix. Firmness of the cervix is scored 0. If it is somewhat softened and indentable, it is scored 1. If the cervix is soft and dilatable, the score is 2. Effacement. The presence of an internal OS is scored zero. If the internal OS has been is effaced to “taken up” and the cervix 80 per cent, a score of 1 is given. An 80 per cent or more effacement yields 2. Position of the cervix. When the cervical canal points directly posterior, the score is 0. If it points about 45 degrees to the axis of the vagina, it is scored as 1. If the cervical canal points directly towards the introitus, the full score of 2 is achieved. Station of the presenting part. If the presenting part is more than 2 ems. above the ischial spines or is floating, it is scored 0. Between 1 cm. above and the level of the spine is scored 1. When the presenting part is well engaged, a full score is given. Dilatation. When the cervix admits only a finger or is closed, the score for dilatation is 0. If the dilatation is 2 or 3 ems., the score is 1, and anything over 3 ems. dilatation is scored 2. Recent increase in vaginal discharge. If the patient gives a history of no change in the vaginal discharge during the week prior to examination, the score is 0. If there is an increase in the amount of mucous discharge, this is scored as 1, but if the discharge is blood tinged it is scored as 2. Prognosis
for
induction
Each of these categories may be evaluated according to the above criteria and given the appropriate score. When added, a rating is obtained. The perfect rating is 20, indicating every possibility that the patient is ready for induction by any modern method. In reviewing 4,461 elective inductions carried out at the Hospital of the University of Pennsylvania during the past 13 years, it would appear that a score of 16 to 20 gives an excellent prognosis. A score of 11 to 15
of
labor
427
indicates that induction can be carried out but may take longer than usual. When elective induction is considered in a nullipara or a breech presentation, the score should be 18 as a minimum rather than 16. When a multipara has a cephalic presentation there is a little more leeway, for a score of 16 results in successful induction. Any patient who receives a score of 10 or less should not be considered for elective induction. If the induction is indicated, preliminary “ripening” at the first session should be considered rather than induction. In these instances, if termination is urgent, cesarean section should be the method of choice. When the patient is finally considered for induction, the readiness for induction is again re-evaluated and the suitability determined by the new score. Results
of clinical
study
To further prove this thesis, a prospective study was undertaken. From December 1963, through April 1965, 332 patients were induced at the Hospital of the University of Pennsylvania. Of these, 264 were elective and 68 were indicated for medical or obstetric complications. Elective induction was performed in 9.7 per cent of 2,724 deliveries and indicated in 2.5 per cent. Each patient was evaluated before induction and the readiness for induction estimated. Indicated inductions which required ripening were graded just before induction was started regardless of the number of days of ripening which preceded. Table I presents the distribution of the inductions according to readiness for induction. Of the 19.9 per cent with readiness for induction of 10 or less most were elective.
Table
I
‘%s$%-
1 No.
o- 10 11 - 15 16-20 Total
of cases 66 176 90
_
332
~
Per
cent 19.9 53.0 27.1
100.0
428
June I, 1966 Am. J. Obst. & Gym.
Fields
Table II. Length
of labor
I
Scores o-
Hours
of
labor
with
No.
II Per
cent
38 22 6
57.7 33.3 9.2
143 28 5
Total
66
100.0
176
Nonoperative Midforceps Cesarean section
I
system 16-20
Per
cent
No.
81.3 16.0 2.7
Per
cent 93.3 5.5
84 5 1
100.0
with
readiness
o- 10 No. 54 10 2
Total
66
IIPer
cent 81.8 15.1 3.1
100.0
Table IV. Complications O-10
11-20
(66)
(266)
Uterine spasm Fetal distress Cervical laceration Postpartum hemorrhage Abruptio placentae
2 2 2
9 2 1
0 1
2 1
Total
7 (10.6%)
1.2
100.0
90
15
No.
for
induction
system
15
16-20 Per
cent 90.0 9.7 0.3
158 17 1
100.0
176
No. 86 4 0 90
Per
cent 95.6 4.4 0
100.0
shorter, and safer the induction, or conversely, the lower the readiness for induction the more difficult, longer, and more dangerous the induction. Comment
(5.6%)
27.1 per cent were in the ideal group to 20). Table II reveals that the longer labors occur with greater frequency in the lower readiness for induction group. These statistics suggest that the lower the readiness for induction the longer the labor. In evaluating the method of delivery, Table III reveals that the lower the readiness for induction, the higher the incidence of operative delivery. Complications also seem to be related to the readiness for induction. A readiness for induction of 10 or below carries with it the risk of complications almost twice that of a higher readiness for induction (Table IV). The above statistics suggest that the higher the readiness for induction the easier, (16
induction
of delivery Scores
Method
for -15
No.
O-6 7 - 12 Over 12
Table III. Method
Only
readiness
10
Such a rating system appears methodical, and it is obvious that there will be individual variations. A few patients with high scores have taken longer than anticipated to be delivered while others with low scores are delivered quickly. The major advantage of the above system or rating readiness for induction is not that it will make induction of labor foolproof but that it will make obstetricians more aware of the factors concerned with induction of labor. This may result in better selection of candidates for induction, and will thus increase the safety of the procedure. Summary 1. A rating system is proposed to indicate “readiness for induction.” 2. The factors composing the system are presented and the method of scoring (0, 1, or 2) is outlined. 3. The ideal score is 20. Elective induc-
Volume Number
95 3
tion should be very successful with any score from 16 to 20 inclusive. From 11 to 15 inclusive, indicated induction may be performed, but the likelihood is that it will be somewhat prolonged. With a score of 10 or below, ripening only should be considered.
Induction
of
labor
429
4. The above thesis is corroborated in a prospective study by analysis of 332 inductions with calculated readiness for induction. 133 South Philadelphia,
36th Street Pennsylvania
HARRY Philadelphia,
FIELDS,
M.D.
Pennsylvania
METHODS TO PREDICT the onset of labor or pinpoint the end of full-term pregnancy have been for the most part inaccurate. Menstrual history, various abdominal measurements, evaluation of the uterine cervix, uterine irritability, and even x-ray examination have been used with little consistent success. Although the cervix is a good indicator of the ease with which a patient may be induced, it is common knowledge that many patients with soft, dilated cervices may carry pregnancies for a month or more without spontaneous labor. If such patients are electively induced on the basis of the “ripeness” of the cervix alone, prematurity of the infant is common, with all the inherent dangers of morbidity and mortality. Since the ripeness of the cervix is not always a good indicator, other means of determining the readiness of a patient for induction must be considered. In a study of induction of labor at the Hospital of the University of Pennsylvania, from 1950 to date, observations have revealed that there are features, other than the condition of the cervix, which should influence the decision as to when to induce a patient. The factors used to determine the readiness for induction are as follows: ( 1) calculated date of confinement, (2) patient attitude, (3) estimated size of the infant, (4) uterine irrita-
bility, (5) softness of the ment, (7) position of the of the presenting part, (10) recent increase in
cervix, (6) effacecervix, (8) station (9) dilatation, and vaginal discharge.
Method of scoring Each one of these factors may be scored as 0, 1, or 2, yielding a maximum score of 20. The combined total represents the patient’s readiness for induction. Calculated date of confinement. If the patient gives a poor menstrual history and the expected date of confinement is uncertain, or she is more than 3 weeks prior to that date, this factor is scored 0. If the history is accurate, the patient is more than one week and less than 3 weeks prior to the estimated date of confinement, she receives a score of 1, and within one week of the estimated date of confinement or after it, the score is 2. Patient’s attitude. If the patient objects to or fears induction of labor, she is scored 0; if she hesitates but accepts elective induction of labor after it is explained to her, 1; and if she requests induction or is enthusiastic about it, she receives a score of 2. Estimated size of the infant. When the infant is considered less than 2,500 grams, the score is 0. If there is some question as to the size of the infant, the score is 1. If the infant is definitely estimated to be well over 2,500 grams, a score of 2 is given. Uterine irritability. Manual abdominal palpation may produce uterine contractions. If the uterus is flaccid following abdominal palpation, this factor is scored as 0. If a certain amount of tension develops as a
From the Department of Obstetrics and Gynecology, School of Medicine, University of Pennsylvania. Read in #art before the Obstetrical Society of Philadelphia, Nov. 7, 1963.
426
Volume Number
95 3
Induction
result of abdominal palpation, it is scored as 1. When the uterus develops a full, firm contraction in response to palpation, it is scored as 2. Softness of the cervix. Firmness of the cervix is scored 0. If it is somewhat softened and indentable, it is scored 1. If the cervix is soft and dilatable, the score is 2. Effacement. The presence of an internal OS is scored zero. If the internal OS has been is effaced to “taken up” and the cervix 80 per cent, a score of 1 is given. An 80 per cent or more effacement yields 2. Position of the cervix. When the cervical canal points directly posterior, the score is 0. If it points about 45 degrees to the axis of the vagina, it is scored as 1. If the cervical canal points directly towards the introitus, the full score of 2 is achieved. Station of the presenting part. If the presenting part is more than 2 ems. above the ischial spines or is floating, it is scored 0. Between 1 cm. above and the level of the spine is scored 1. When the presenting part is well engaged, a full score is given. Dilatation. When the cervix admits only a finger or is closed, the score for dilatation is 0. If the dilatation is 2 or 3 ems., the score is 1, and anything over 3 ems. dilatation is scored 2. Recent increase in vaginal discharge. If the patient gives a history of no change in the vaginal discharge during the week prior to examination, the score is 0. If there is an increase in the amount of mucous discharge, this is scored as 1, but if the discharge is blood tinged it is scored as 2. Prognosis
for
induction
Each of these categories may be evaluated according to the above criteria and given the appropriate score. When added, a rating is obtained. The perfect rating is 20, indicating every possibility that the patient is ready for induction by any modern method. In reviewing 4,461 elective inductions carried out at the Hospital of the University of Pennsylvania during the past 13 years, it would appear that a score of 16 to 20 gives an excellent prognosis. A score of 11 to 15
of
labor
427
indicates that induction can be carried out but may take longer than usual. When elective induction is considered in a nullipara or a breech presentation, the score should be 18 as a minimum rather than 16. When a multipara has a cephalic presentation there is a little more leeway, for a score of 16 results in successful induction. Any patient who receives a score of 10 or less should not be considered for elective induction. If the induction is indicated, preliminary “ripening” at the first session should be considered rather than induction. In these instances, if termination is urgent, cesarean section should be the method of choice. When the patient is finally considered for induction, the readiness for induction is again re-evaluated and the suitability determined by the new score. Results
of clinical
study
To further prove this thesis, a prospective study was undertaken. From December 1963, through April 1965, 332 patients were induced at the Hospital of the University of Pennsylvania. Of these, 264 were elective and 68 were indicated for medical or obstetric complications. Elective induction was performed in 9.7 per cent of 2,724 deliveries and indicated in 2.5 per cent. Each patient was evaluated before induction and the readiness for induction estimated. Indicated inductions which required ripening were graded just before induction was started regardless of the number of days of ripening which preceded. Table I presents the distribution of the inductions according to readiness for induction. Of the 19.9 per cent with readiness for induction of 10 or less most were elective.
Table
I
‘%s$%-
1 No.
o- 10 11 - 15 16-20 Total
of cases 66 176 90
_
332
~
Per
cent 19.9 53.0 27.1
100.0
428
June I, 1966 Am. J. Obst. & Gym.
Fields
Table II. Length
of labor
I
Scores o-
Hours
of
labor
with
No.
II Per
cent
38 22 6
57.7 33.3 9.2
143 28 5
Total
66
100.0
176
Nonoperative Midforceps Cesarean section
I
system 16-20
Per
cent
No.
81.3 16.0 2.7
Per
cent 93.3 5.5
84 5 1
100.0
with
readiness
o- 10 No. 54 10 2
Total
66
IIPer
cent 81.8 15.1 3.1
100.0
Table IV. Complications O-10
11-20
(66)
(266)
Uterine spasm Fetal distress Cervical laceration Postpartum hemorrhage Abruptio placentae
2 2 2
9 2 1
0 1
2 1
Total
7 (10.6%)
1.2
100.0
90
15
No.
for
induction
system
15
16-20 Per
cent 90.0 9.7 0.3
158 17 1
100.0
176
No. 86 4 0 90
Per
cent 95.6 4.4 0
100.0
shorter, and safer the induction, or conversely, the lower the readiness for induction the more difficult, longer, and more dangerous the induction. Comment
(5.6%)
27.1 per cent were in the ideal group to 20). Table II reveals that the longer labors occur with greater frequency in the lower readiness for induction group. These statistics suggest that the lower the readiness for induction the longer the labor. In evaluating the method of delivery, Table III reveals that the lower the readiness for induction, the higher the incidence of operative delivery. Complications also seem to be related to the readiness for induction. A readiness for induction of 10 or below carries with it the risk of complications almost twice that of a higher readiness for induction (Table IV). The above statistics suggest that the higher the readiness for induction the easier, (16
induction
of delivery Scores
Method
for -15
No.
O-6 7 - 12 Over 12
Table III. Method
Only
readiness
10
Such a rating system appears methodical, and it is obvious that there will be individual variations. A few patients with high scores have taken longer than anticipated to be delivered while others with low scores are delivered quickly. The major advantage of the above system or rating readiness for induction is not that it will make induction of labor foolproof but that it will make obstetricians more aware of the factors concerned with induction of labor. This may result in better selection of candidates for induction, and will thus increase the safety of the procedure. Summary 1. A rating system is proposed to indicate “readiness for induction.” 2. The factors composing the system are presented and the method of scoring (0, 1, or 2) is outlined. 3. The ideal score is 20. Elective induc-
Volume Number
95 3
tion should be very successful with any score from 16 to 20 inclusive. From 11 to 15 inclusive, indicated induction may be performed, but the likelihood is that it will be somewhat prolonged. With a score of 10 or below, ripening only should be considered.
Induction
of
labor
429
4. The above thesis is corroborated in a prospective study by analysis of 332 inductions with calculated readiness for induction. 133 South Philadelphia,
36th Street Pennsylvania