In current obstetric practice, induction of labour is often carried out for various maternal and/or fetal reasons


Chart 4 : ANC visits in high BS group



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Chart 4 : ANC visits in high BS group
In the present study, majority had ANC attendance i.e. 92% in the low BS group and 93% in the high BS group (P=1.0). There was no difference of ANC attendence between the two study groups.

SOCIO - ECONOMIC STATUS (SES)



Chart 5 : SES in low BS group



Chart 6 : SES in high BS group

There was no statistical difference in the percentage of women of the three socio-economic classes in the two study groups. This merely reflects the obstetrics-care seeking by the pregnant women from the different socio-eonomic strata within the catchment area of the Thapathali's Maternity Hospital.



TABLE II : INDICIATIONS FOR INDUCTION IN RELATION TO BISHOP SCORE



Indication
Score___0-4__(n=16)__5-8__(n=42)'>Score___0-4___5-8___P'>Bishop Score


0-4


5-8


P

(< 0.05)

POST-DATES

64.58 %

76.36 %

NS

HDP

12.50 %

10.90 %

NS

NIGGLING PAIN

12.50 %

9.09 %

NS

LESS FM

6.25 %

3.63 %

NS

SFD

2.08 %

--




OLIGOHYDRAMNIOS

2.08 %

--




Total

100.00 % (n=48)

100.00 % (n=55)



Postdates (Overdue by dates, post - EDD) was the leading indication for induction, comprising of 64.58% women among low BS group and 76.36% women in high BS group. The indications were similar in both the study groups, the difference being not significant statistically.



TABLE III : OUTCOME OF INDUCTION ACCORDING TO BISHOP SCORE



Outcome
BS


0-4

(n=48)

5-8

(n=55)

P

(< 0.05)

Failed Induction

43.75 % (21/48)

9.09 % (5/55)

S

Vaginal Delivery

33.33 (16/48)

76.36 % (42/55)

S

LSCS

22.91 % (11/48)

14.54 (8/55)

S

Total

100.0 %

100.0 %







  • The overall failure rate was 25.2% (26/103).

The failure rate was significantly higher (P=.0000) in the low BS (0-4) group than in the high BS (5-8) group. The vaginal delivery rate was lower in the low BS group whereas the CS rate was higher in the low BS group. Thus, the women with low BS had high failure rate and more operative delivery rate in the present study.

TABLE IV : MEAN IDI IN RELATION TO BISHOP'S SCORE

(Controlled for parity)



Parity
Score


0-4

(n=16)

5-8

(n=42)

P

(< 0.05)

0

12.81 hours

 3.58


9.32 hours

 3.23

S


1

10.61 hours

 2.62


8.12 hours

 2.85

S


Overall

11.16 hours

 3.04


9.02 hours

 3.15

S


  • Cases in which CS was performed were omitted in calculation of the IDI.

  • Data presented as mean  SD.

The women with low Bishop's score had significantly (p=0.0281) longer mean IDI than those with high BS (11.16 hr Vs 9.02 hr).


Nulliparas in both the groups had longer mean IDI than that of multiparas. So, parity was inversely related to the mean IDI. Thus nulliparous women with low BS had longer mean IDI in the present study.
TABLE V : MODE OF DELIVERY IN RELATION TO BISHOP SCORE


Mode of

Delivery
Bishop Score


0-4

(n=27)

5-8

(n=50)

P

(< 0.05)

Vaginal Delivery

59.25% (16/27)

84.0 % (42/50)

0.0162

LSCS

40.74 % (11/27)

16.0% (8/50)

0.0162

Total

100.0 % (27/27)

100.0 % (50/50)




  • Cases of failed induction were omitted in calculation of mode of delivery.

Vaginal delivery rate was significantly higher (P=0.0162) in the high BS groups as compared to the low BS group. However, the CS rate was significantly lower (P=0.0162) in the high BS group than in the low BS group. Therefore, women with high BS at induction had better outcome as compared to those with low BS at induction.


TABLE VI : DISTRIBUTION OF LSCS ACCORDING TO BISHOP SCORE (Controlled for parity)


Score
Parity


0

1

P

(< 0.05)

0-4 (n = 27)

33.3% (9/27)

7.40% (2/27)

S

5-8 (n=50)

16.0% (8/50)

0 % (0/50)

S

  • Cases of failed induction were omitted in calculation of LSCS.

In total, about 40% women in the low BS group had LSCS, whereas only 16% women in the high BS group had LSCS. The difference is significant (P=0.0162) statistically.

On parity-wise analysis, in the low BS group nulliparas had significantly higher (P=0.0426) CS rate as compared to multiparas. Similarly, in the high BS group also nulliparas had significantly higher (P=0.0057) CS rate as compared to multiparas. Thus, nulliparas in both the study groups had higher CS rate, as compared to multiparas.

TABLE VII : MATERNAL COMPLICATIONS IN RELATION TO BISHOP SCORE


Type
Score

0-4

(n=27)

5-8

(n=50)

P

(< 0.05)

No Complication

88.8 %

88.0 %

NS

PPH

11.1 %

0 %

S

Pyrexia

0 %

6.0 %

NS

Genital Tract Injury

0 %

6.0%

NS

Total

100.0 %

100.0 %




  • Cases of failed induction were omitted in calculation of complications.

The majority did not have complications in both the study groups. Women with low BS did not have pyrexia and genital tract injury but the difference was not significant statistically (P=0.5478). Eleven percent in the low BS group had PPH, but none had PPH in the high BS group. The difference was significant statistically too (P=0.0399).


TABLE VIII : APGAR SCORE AT BIRTH IN RELATION TO BISHOP SCORE (at one minute)


Apgar Score
Bishop

Score

0-4

(n=27)

5-8

(n=50)

Overall

P

(< 0.05)

0-3

3.7

4.0

3.89

NS

4-6

44.4

30.0

35.0

NS

7-10

51.8

66.0

61.0

NS

TOTAL

100.0

100.0

100.0






  • Data presented as percent of total numbers of cases in each group.

The majority had good Apgar score (7-10) at 1 minute, i.e. 52% in the low BS group and 66% in the high BS group. However, the difference was not significant (P=0.2244). Very low Apgar score (0-3) at one minute was found to be 3.7% and 4.0% in the low BS group and in the high BS group respectively. There was also no significant difference in between the groups (P=0.9488).


TABLE IX : APGAR SCORE AT FIVE MINUTES IN RELATION TO BISHOP SCORE


Apgar Score
Bishop

Score

0-4

(n=27)

5-8

(n=50)

Overall

P

(< 0.05)

0-3

0

0

0




4-6

0

4

2.59

NS

7-10

100.0

96

97.4

NS

Total

100.0

100.0

100.0







  • Data presented as percent of total numbers of cases in each group.

None had very poor Apgar score at 5 minutes in either groups. Only 4% had an Apgar score of 4-6 in the high BS group but none in the low BS group. The difference was insignificant (P=.5386).


Cent percent in the low BS group and 96% in the high BS group had good Apgar score (7-10). The difference was insignificant too (P=.5386).
TABLE X : SCBU (BABY UNIT) ADMISSIONS IN RELATION TO BISHOP SCORE


Duration
Bishop

Score

0-4

(n=27)

5-8

(n=50)

Overall

P

(< 0.05)

No Admission

70.3

84

79.2

NS

 24 hours

14.8

12

12.9

NS

> 24 hours

14.8

4

7.7

NS

Total

100.0

100.0

100.0




  • Data presented as percent of total numbers in each group.

  • No SB/NND/Congenital anomaly observed.

Only about 20% new-borns needed baby unit admission; very few (i.e. 7.7%) needed longer stay of > 24 hours in the baby unit.


In the low BS group, 29.6% needed admission, half of them (i.e. 14.8%) needed longer stay, whereas in the high BS group, only 16% needed admission, and 1/4 (i.e. 4%) needing longer stay. So, more babies in the low BS group needed SCBU admission and more stayed longer as compared to the high BS group. But these differences were not significant statistically.

In the present study with the induction rate of 3.7%, various outcome parameters of induction of labour were studied.


The rate of induction varies greatly. A rate of 4% in one centre in Britain compared to 40% in another centre exemplifies the variation 18. The reason for a low rate in our study was not clear but it might be due to obstetricians' reluctance of induction unless there is a valid indication.
In National Maternity Hospital, Dublin the induction rate has declined from 31% in the year 1971 to 12.1% in 1979, and in Simson Pavilan hospital, the incidence has declined from 54% in 1974 to 26% in 1980 3.
In a Singaporean study, the induction rate was 9.8% 19 and in a recent survey from Finland it was 19.5% 20. Similarly in an Indian study, the rate was 11.4% 21.
Indications for induction of labour are fetal, maternal or both and at times social. Fetal reasons constitute the large majority of indications. The fear of poor perinatal outcome in epidemiological studies is more often an important factor. The indications for 103 cases of induction of labour in the present study are shown in table II. In the present series, the major indication for induction was postdated pregnancy with a 70.8% of all induced labours followed by HDP (11.6%), niggling pain (10.6%), less fetal movement (4.8%) and others (1.9%). The indications did not differ significantly by Bishop category in both the study groups.

In Simpson Pavilian Hospital, post-maturity was the commonest indication (54%) followed by pre-eclampsia/hypertension (28%), accidental haemorrhage (5%), rhesus iso-immunisation (3%) 3. In a Finnish study, HDP (40%) was the most common indication followed by post-dated pregnancy (27.5), intra-uterine growth retardation (11.5%), fetal deaths (5%) and others 20. But, in an Indian study, the indications were mainly post-term pregnancy (72%) and uncontrolled


hypertension (25%) 21.
In Arulkumaran and his colleagues' study, static weight or weight loss at term was the major indication of IOL comprising 33.7% of induced patients, followed by mild pre-eclampsia (22.7%) and prolonged pregnancy (9.5%)19.
In our study, postdate was major indication. This might be due to the practice of early induction at 40+ weeks by the obstetricians which may be because of lack of facilities for intensive fetal surveillance for postdated pregnancies.
In the present study, the overall failed induction rate was 25.2% (26/103), and majority of the failures was in the nulliparous women (20%).
When analysed by the Bishop score, 43.75% of the low BS group patients experienced failure compared to only 9.09% of those from the high BS group. This is shown in table III. Parity showed a strong relation to the success of induction. In a Singaporean study, overall failed induction rate was 7% in patients induced with amniotomy and syntocinon 19.
In a collaborative study by Hendricks et al, failure of attempted induction exceeded 20% among patients with a very low BS, and a BS of 8 being associated with only 3% failures23.
The higher failure rate in the present study may be because of higher number of nulliparas included in this study, lack of use of cervical primers like prostaglandins prior to induction and delayed amniotomy only in the active stage of labour.
Bishop score at induction and parity are important factors which influence the mean induction delivery interval. This was well demonstrated in the present study. The women with a low BS had significantly longer IDI as compared to women with the high BS (11.16 hrs Versus 9.02 hr). Nulliparas in both the study groups had longer mean IDI than multiparas as shown in table IV.
In a study of primigravidae whose labour was induced by amniotomy and oxytocin, it was found that the mean IDI was higher in women with a low cervical score of
0-3, than in women with high score of 4-7 (14.9 hrs Versus 8.9hrs)9. Pant and her colleagues found that the BS was directly related to the mean IDI. In their study, the women with a low BS (0-4) had a mean IDI of 12.30 hrs and those with a score of 5-8, had a mean IDI of 9.5 hrs27.

In agreement with our study, many studies also showed a longer IDI in nulliparus women than in multiparous women. Mukherjee and his colleagues reported the mean IDI, in women with the BS of less than 5, to be 22.5 hrs and 12.4 hrs in primigravidas and multigravidas respectively 29.


Similarly, Mishra and her colleagues found mean IDI to be 11.35 hrs in primigravidas and 7.99 hrs in multigravidas, all of them had a pre-induction BS of less that 3 21.
A Singaporean study showed the mean length of labour in women with low cervical score (0-3) to be 10.8 hrs and 7.1 hrs in primigravidas and multigravidas respectively. Similarly in 4-6 scores group it was 8.6 hrs and 5.2 hrs in primigravidas and multigravidas respectively 10.
In those studies, the mean IDI was longer in patients with low score at induction, may it be Bishop score or its modified version.
This also applied equally to the present study in which women with low BS had significantly longer IDI than those with a high BS.
The risk of caesarean section is greater in the induction group than in the spontaneous labour group. Thus the greatest maternal risk of induction of labour is the risk of morbidity associated with CS for various reasons and the risk increases with the decrease in parity and also with the decrease in the favourability of the cervix at induction. This was well demonstrated in the present study in which the CS rate was significantly higher in women with low BS group than in the high BS group (23% Versus 14.5%) as shown in table III and nulliparas in both the groups of the study had a higher CS rate as compared to multiparas, as shown in table VI.
These findings are consistent with the findings of many studies from various parts of the world.
In an Indian study, Pant and her colleagues reported a CS rate of 40% in induced labour with a low BS (0-4) score and a CS rate of 15% in women with a BS
of 5-827.
In another study of induced labour using an integrative approach (prostaglandin, amniotomy, oxytocin), it was found that the women who had a BS of 3 or less had higher CS rate than those with a BS above 3 (29% Versus 15.4%)32.
The findings of their study are close to that of our study but prostaglandin and initial amniotomy were not used in the present study.
In a study of primigravidas whose labour was induced by amniotomy and oxytocin, the CS rate, in women with a low cervical score (0-3) was reported to be 32% where as it was only 4% in women with a score of 4-7. That study used cervical score instead of BS and only primigravidas were studied9.
Macer JA and his colleagues reported that the BS did not affect the CS rate for multiparous women. However nulliparous women with a BS  5 had higher CS rate than those with BS > 5, 50% compared with 26%30.
Misra et al in a study of induced labour with a modified BS of 0-3, reported the CS rate of 47.2% and 14.6% in primigravidas and multigravidas respectively 21. In a study by Kurup and his colleagues, the CS rate was 48.6% in those with a poor cervical score (5) compared with 8.8% in those who had a good score ( 6)31. In a study carried out in Singapore the CS rate in multiparas and nulliparas with a good cervical scores (7-10) was not high. However nulliparas with a cervical score of 3 or less had a CS rate of 65% for all indications (45.8% for failed induction). Multiparas with the same cervical score (< 3) had a CS rate of 7.7% only. In the same study, nulliparas with a cervical score of 4-6 had a CS rate of 10.3%, whereas multiparas with cervical score of 4-6 had a CS rate of 3.9%. In that study nulliparas had a higher CS rate than multiparas and women with low score had higher CS rate 10.
The vaginal delivery rate including the instrumental delivery was higher in the high BS group than in the low BS group (84% Versus 59%) in our study. Calder in his study found the vaginal delivery rate of 68% in women with low pre-induction cervical score (0-3) and 96% in women with a score of 4-79. Pant and her colleagues reported the vaginal delivery rate in women with a low BS (0-4) was lower than in women with a high BS (5-8) (60% Versus 84%)27. These findings are quite close to our findings in the present study.
Another study of oxytocin induced labour in women with a low modified BS (0-3) showed a vaginal delivery rate of 52.8% and 85.4% in the primigravida and multigravida respectively21.
Many studies of induced labour showed some maternal complications of induction of labour by oxytocin infusion.
In the present study, the majority did not have complications in both the study groups (88.8% in low BS group Versus 80% in the high BS group). Women with low BS did not experience pyrexia and genital tract injury but 11% women in this group had PPH which was significant. In the high BS group, few women had pyrexia and genital tract injury (not significant statistically), none had PPH.
In a study of induced labour by Xenakis et al maternal complications associated with induction were infrequent and did not differ by Bishop category. Chorio-amnionitis was the most common complication occurring in 3.5% of the 0-3 Bishop score group and 4% of the 4 and above Bishop group. All other complications (hyperstimulation, PPH, hysterectomy) occurred in 2% or less population. Overall 93% of the women experienced no complication 32.
In an Indian study, vomiting was observed in 4.8% and hyperstimulation in 9.5% women with low BS (<5) induced by oxytocin33. Other studies showed the side effects of oxytocin in induced labour were rare 9,29.
The fetal/neonatal outcome in induced labour was generally good with no stillbirth and early neonatatal deaths.
In the present study there was no stillbirth and early neonatal death. Apgar score of 7-10 at one minute was found to be in 52% in the low BS group and 66% in the high BS group with no congenital anomalies. The difference was not significant statistically. Very low Apgar score of 0-3 at one minute was found to be in 3.7% in the low BS group and 4% in the high BS group and the difference was also insignificant. Similarly, Apgar score of 7-10 at 5 minute was found to be cent percent in the low BS group, and 96% in the high BS group. None had a very poor (0-3) Apgar score at 5 minutes in either group.
Regarding the baby unit admission, the majority did not need SCBU admission, only about 20% newborns needed admission; very few (i.e. 7.7%) needed longer stay of > 24 hours in the baby unit, and there was no significant difference between the study groups regarding the SCBU admission and the duration of stay.

Macer JA et al in their study found that all babies were born alive and there was no neonatal deaths in the induction group. Neonatal intensive care unit admission was only in 0.8% babies 30. In a study the neonatal outcome was reported to be good with 5 minute Apgar score of < 7, only in 3.2% babies of women induced by traditional oxytocin protocol 25.


In a few studies, neonatal hyperbilirubinemia and neonatal sepsis were found in cases of induced labour 23, 35.
In another study, one minute Apgar score < 5 was found in 23% and 6% patients with cervical score of 0-3 and 4-7 groups respectively 9.
Women with poor cervical score had a poor neonatal outcome in a Singaporean study in which one minute and 5 minute Apgar score was slightly but not significantly lower in those with poor cervical scores, especially in multigravidas only 4.7% neonates were admitted to the SCBU 10.

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