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The use of castor oil to stimulate labor in patients with premature rupture of membranes
THEUSEOFCASTOROILTOSTIMULATELABORINPATIENTS WITHPREMATURERUPTUREOFMEMBRANES
Lorna Davis, CNM,
MSN
ABSTRACT Induction of labor is often necessary in patients with premature rupture of membranes. While the effect of oxytocin to stimulate labor is well established, it is potentially hazardous to both the mother and infant. In this study, castor oil was evaluated as a method to induce labor in uncomplicated patients at term gestation with premature rupture of membranes. A total of 196 patients with premature rupture of membranes was studied retrospectively. Of 107 patients who received castor oil, 75% went into labor as compared to 58% of 89 control patients who went into labor spontaneously (P < 0.02). On the basis of these results, it is concluded that castor oil, which is more economical and convenient than oxytocin, can be used safely and effectively to stimulate labor.
Castor oil was first noted to have oxytocic properties by ancient Egyptians,l and remained a very popular stimulant for the induction of labor until the mid-1950s.2-6 Specific reasons for the decline in the use of castor oil thereafter are not apparent
in the literature. However, it seems likely that the decline was due primarily to the introduction and widespread use of oxytocin. There have been only two clinical trials published on the use of castor oil as a means of inducing labor. In 1958, Nabors7 evaluated the effectiveness of castor oil in combination with pitocin and artificial rupture of membranes. He demonstrated slightly fewer failed inductions in the
*This paper is adapted from a presentation made at the 28th Annual Convention of the AmericanCollegeof Nurse-Midwives,Los Angeles, CA, May 1983. Data obtained from Maternity Center Association, New York, New York. Address correspondence to Lorna Davis, CNM, 250 Mercer Street, New York, NY 10012.
group that was given castor oil, but concluded that castor oil was of no real value in the induction of labor. The subjects in this trial were all highrisk patients; they were not at term gestation, and their cervices were not considered “ripe.” The inductions were considered obligatory because of definite obstetrical indications such as preeclampsia and hypertension. In 1959, Mathie and Dawson8 published a more favorable opinion of castor oil. They measured the contractility of the uterus after the administration of castor oil and demonstrated a marked increase in uterine activity. The authors felt the castor oil could expedite the spontaneous onset of labor or increase the effectiveness of other methods of induction, and they concluded that it should continue to be used for this purpose. The benefit of oxytocin to stimulate labor is well established and is essential in inductions for numerous medical indications. However, it is potentially hazardous to both the inJournal
366 Copyright
0 1984 by the American
College of Nurse-Midwives
of Nurse-Midwifery
l
fant and mother and is neither as convenient nor as economical as castor oil. Observations at this birth center suggested that castor oil could safely stimulate labor, and therefore still had a place in obstetrical practice. This study was designed to evaluate the capability of castor oil to stimulate labor in medically uncomplicated patients at term gestation with premature rupture of membranes (PROM). MATERIALS
AND
METHODS
The data for this study were obtained retrospectively by reviewing all charts of patients admitted to an out-of-hospital
birthing
center
from
1976
through 1981. Maternity care at this center is provided by a team of certified nurse-midwives and obstetricians and is offered to carefully screened low-risk mothers. Some maternal complications that exclude the mother from receiving birth center care include hypertension, diabetes, cardiac disease, anemia, mulVol. 29, No. 6, November/December
1984
0091-2182/84/$03.00
tiple pregnancy, labor onset occurring at less than 37 weeks gestation, nonvertex presentations, meconium staining, and ruptured membranes for longer than 24 hours. If the patient becomes ineligible for care according to the risk criteria, she is transferred to a hospital where one of the birth center’s three obstetricians assumes responsibility for her care. All patients studied had uncomplicated medical and obstetrical histories and singleton, vertex presentations with PROM between 37 and 42 weeks gestation. In this study, the term PROM is used to define the spontaneous rupture of membranes at term gestation occurring before the onset of labor. It was diagnosed on the basis of gross leakage of fluid, ferning, or a positive nitrazine test. Labor was defined as the onset of regular contractions resulting in cervical dilation and effacement. Prior to 1978, the policy at the birth center regarding PROM was to await labor onset without administering any intervention; all women in this group with ruptured membranes became the control group. Subsequently, the medical board approved a policy prescribing that all patients presenting with PROM and a latency period of at least four hours be given 2 oz of castor oil orally. There was no selection process used once this policy changed; this group constituted the experimental group. All patients during this study period, 1976-1981, were observed for labor onset for 24 hours after PROM. If labor did not occur during this
time, the patients were transferred to a hospital for oxytocin stimulation. The longest interval between rupture of membranes and subsequent delivery was 48 hours. The doses of oxytocin required to effect cervical dilation were not available and therefore were not evaluated. In addition to assessing whether castor oil stimulated labor, factors that might have influenced the effectiveness of castor oil were also evaluated. Parity, bishop score (evaluation of the cervix for ripeness), gestational age of patients, and birthweight of the infant were all assessed individually. Bishop scoring was done weekly beginning at 36 weeks; the score evaluated in ths study was the one from the most recent pelvic examination prior to rupture of membranes. Furthermore, the outcomes of the labors in the two study groups were analyzed for method of delivery, need for oxytocin intervention, Apgar scores of the infants, and the presence of meconium. Of 196 patients studied, 107 received castor oil, and 89 did not. Most patients were white, predominantly middle- and upper-class women with a mean age of 28 years. There were 160 primiparas and 36 multiparas. Data were analyzed for statistical significance by a t-test to individually evaluate multiple factors on a single dependent variable.
TABLE
RESULTS
During the years 1976 through 1981, 196 patients between 37 and 42 weeks gestation with ruptured membranes for at least four hours and not in labor were treated at the birth center. There were 160 primiparas, which is reflected in the low Bishop scores (Table 1) and 36 multiparas. The patient characteristics of the two groups are shown in Table 1. The two groups did not differ with respect to patient age, parity, gestational age, or Bishop score. Table 2 demonstrates an association between castor oil administration and an increased frequency of labor onset. In the castor oil group, 80 of 107 patients (75%) had labor onset while only 52 of 89 patients (58%) in the control group had spontaneous labor. This difference is sig-
nificant at P < 0.05. The time from administration of castor oil to onset of labor ranged from 1 to 13 hours, with a mean of 4 hours. Factors that might influence the effectiveness of castor oil were also examined. The significance of parity, Bishop scores, birthweight of the infant, and gestational age appear in Table 2. The effects of castor oil were most pronounced among primiparas; 75% of the experimental group primiparas went into labor compared with the control group in which only 54% of the primiparas had spontaneous labor. This is a significant
1
Patient characteristics Castor
oil
(n = 107) Loma
Davis,
CNM,
MSN
graduated
from
the Saint Louis Univeristy nursemidwifery program in 1978. After working for the Maternity Center Association for three years, she joined a priuate practice Kraus,
practice. She is current/y in in New York City with Nancy CNM, Joanne Monson, CNM, Marcia Starch, MD, Shelley Kolton, MD, and Beth Shimlock, MD.
Control (n = 89)
Factor
Mean
SD
Mean
Age Gravidity No. of term births No. of premature births No. of abortions No. living children Gestational age Bishop score
28.6 1.9 0.2 0.0 0.7 0.2 39. 3.6
7.9 1.2 0.6
27.6 2.0 0.2 0.0 0.9 0.2 39. 3.0
1.0
0.6 1.2 3.9
SD
3.8 1.1 0.4 0.9 0.4 1.3 2.5
Level of significance NS NS NS NS NS NS E
NS, Not significant.
Journal
of Nurse-Midwifery
l
Vol. 29, No. 6, November/December
1984
367
TABLE
2
Patient characteristics
extrapolation of this data to all women, which should be done with caution.
and frequency of labor Castor oil group
Control group
No. in labor/
Level of
No. in labor/ total no.
%
total no.
%
significance
Total no. of patients Patient characteristics Primiparas Multiparas Bishop: O-4 Bishop: 5-9 Birthweight 2100-3099 g Birthweight 3100-3900 g Birthweight 3901-4999 g
80/107
74.8
52189
58.4
P < 0.05
66188 14/19
75.0 73.7
46164
71.9
31/40 13/19
39172 13/17 35163 17126
68.4
12/19
80.6 68.4
31/48 418
54.2 76.5 55.6 65.4 63.2 64.6 50.0
P < 0.01 NS NS NS NS NS NS
Weeks gestation 39-40 37-38 Weeks gestation 41-42
48164 19125
76.0 75.0 72.2
32145 18130 2114
60.0 71.1 14.3
E P < 0.01
54167 13/19 13/18
77.5
NS, Not significant.
finding, with P < 0.01 (Table 2). Castor oil was significantly associated with onset of labor at gestational ages 41-42 weeks (P < 0.01). The incidence of labor within 24 hours in the castor oil group and the control group was not significantly different for multiparas, Bishop score categories, birthweight distributions, and gestational ages 37-40. In addition to examining factors that may influence the effect of castor oil, labor outcomes were also evaluated for type of delivery, incidence of oxytocin stimulation, and infant wellbeing, as evidenced by Apgar scores and presence of meconium. There were nearly three times as many cesarean sections in the control group (15.7%) compared to the castor oil group (5.6%), percentages that differ significantly, P < 0.01. The castor oil group did not require oxytocin stimulation (36%) as frequently as did the control group (43%), but the difference was not significant. Of the 38 patients in the castor oil group who needed oxytocin stimulation, 27 were patients who did not have any contractions after the administration of castor oil and another 11 were patients who had contractions that were inadequate to cause cervical dilation. This compares with 37 patients in the
control group who did not go into labor and one patient who had inadequate contractions. Infant outcomes were examined in the two groups by noting Apgar scores at one and five minutes and by determining whether meconium staining was present. There were two infants in both groups with Apgar scores less than seven at one minute and the two in the control group remained less than seven at five minutes. The presence of meconium at the time of rupture of membranes in the two groups was very low, and no one developed meconium staining after the administration of castor oil. In addition to the good infant outcomes, there was no significant maternal morbidity and no maternal deaths. The expected side effect of castor oil, diarrhea, did occur in almost everyone; however, maternal dehydration and electrolyte imbalance were not problematic. Limitations
of the Study
A limitation of this study is the lack of randomization and, therefore, the potential problem of bias and dissimilar groups. In addition, this unique population of women who sought out-of-hospital maternity care limits
Journal
of Nurse-Midwifery
l
COMMENT
These data indicate that patients at term gestation presenting with PROM benefit from the administration of castor oil by stimulating labor. These findings support the clinical observations made at the birth center and are consistent with the research of Mathie and Dawson* in which they reported a marked increase in the contractility of the uterus after the administration of castor oil. Currently, there is no information on the mechanism by which castor oil acts to stimulate contractions. It is thought to work by causing violent intestinal peristalsis, which, by some means, excites the uterus. Luderer et allo in 1980 reported on the mechanism of action of castor oil. They documented by in vivo studies on rats a significant increase in portal venous prostaglandin E concentration after the oral administration of castor oil. The authors concluded that castor oil may induce its cathartic effects by serving as exogenous substrate for intestinal prostaglandin synthesis It may be that there is a relationship between intestinal prostaglandin synthesis produced by castor oil and its effect on the uterus. Patients who took castor oil went into labor more frequently than patients in the control group. However, the effectiveness of the contractions produced by castor oil to accomplish cervical dilation needs further evaluation. In the 80 patients who labored with castor oil, 11 had uterine contractions that were inadequate to dilate the cervix and the patients required further stimulation with oxytocin. There was only one patient in the group who had spontaneous labor that needed further stimulation by oxytocin. This suggests that castor oil stimulated labors may not be as effective as spontaneous labors.
Vol. 29, No. 6, November/December
1984
Parity, Bishop score, birthweight of the infants, and gestational age were factors evaluated individually for their influence on castor oil and spontaneous labor. Among primiparas, the castor oil group had a 75% onset of labor, whereas the control group had a spontaneous labor rate of 58%. Surprisingly, this labor difference was not true among multiparas, primarily due to a high spontaneous labor rate of 77%. The state of the cervix has been shown to relate to successful induction of labor.g Bishop scores of the patients in this study were all less than nine and did not have a significant influence on the effect of castor oil. Birthweight of the infants also did not have an effect on castor oil to stimulate labor. Postdatism is a factor that did appear to produce a significant difference, as seen in the 41-42 week gestational age group. Only 2 of 14 patients in this group went into labor spontaneously, compared with 13 of 18 patients in the castor oil group. This low spontaneous labor rate was unexpected and the explanation for this significant difference is not apparent. The need for oxytocin stimulation and the incidence of cesarean sections were examined in the control group and the castor oil group. Although there was a higher incidence of oxytocin stimulation in the control group, it was not significant. More importantly though, the group who received castor oil had significantly fewer cesarean sections. All patients in both groups who had a cesarean section first received a trial of oxytocin stimulation. The indications for cesarean section were cephalopelvic disproportion (2 patients) and failure to progress (18 patients). Individual practitioner judgment could not be well controlled, but the physicians who made the decisions to perform the cesarean sections remained constant throughout the five-year study period. One theory to explain the low cesarean section rate in the castor oil group is that castor oil may
Journal
of Nurse-Midwifery
l
ripen the cervix, resulting in fewer failed inductions, and therefore fewer cesarean sections as noted by Nabors’ study7 in 1958. There was no maternal or fetal morbidity in either group. There was one suggestion in the literature that meconium staining occurred after the administration of castor oil.‘l However, no one in this study developed meconium-stained amniotic fluid after the administration of castor oil. There are many disadvantages of oxytocin intervention when compared with the convenience, safety, and cost-effectiveness of castor oil. Neonatal jaundice is often cited as a problem in infants after oxytocin stimulation. 12,13 Granat et al. l4 in 1981 demonstrated an association between the mean total dose of oxytocin used for induction and the incidence of byperbilirubinemia. Brinsden and ClarkI in 1978 documented an increased risk of maternal postpartum hemorrhage after oxytocin stimulation. There have been several authors reporting an increased incidence of operative deliveries with the use of oxytocin.16x17 Oxytocin stimulation requires hospitalization and the attention of specially trained personnel. The patient must be confined to bed due to maternal and fetal monitoring, which is essential with oxytocin stimulation. Bimanual examinations are necessary to monitor progress and for the insertion of fetal electrodes and internal pressure catheters, which are often necessary for accurate monitoring. Many studies indicate an increased risk of fetal infection, amnionitis, and endometritis in those patients who recieve internal monitoring. 18,1g In this study everyone who received oxytocin stimulation also required analgesics. There were only five patients who required analgesics in the group that did not get oxytocin. All analgesics carry some risk to the mother and infant and may result in additional cost. When considering the potential hazards of oxytocin, the inconve-
Vol. 29, No. 6, November/December
1984
nience to the patient and physician, the added expense, and the increased likelihood of a cesarean section, the conservative approach of first using castor oil in patients with PROM seems quite justified. In view of these facts, it is recommended in low-risk populations with PROM that 1) there be an appropriate waiting period for spontaneous labor, 2) if no labor occurs, dispense orally 2 oz of castor oil, and 3) if no labor occurs within 13 hours after the administration of castor oil, oxytocin stimulation should be considered.
This paper is dedicatedto the former nursemidwiferyprogram at Saint Louis University.
REFERENCES
1. La Wall CH: Four thousand years of pharmacy. Philadelphia: JB Lippincott
Company, 1927. 2. Goodman LS, Gilman A: The pharmacological basis of therapeutics. New York: The Macmillan Company, 1941. 3. Watson BP: Am J Obstet Gynecol 1: 70, 1920. 4. Hewitt J, Towart D, Baird D: J Obst Gynaec Brit Emp 34520, 1927.
5. Stander HJ: Williams obstetrics, 7th ed. New York: Appleton-CenturyCrofts, Inc, 1936, p. 529. 6. Atlee HB: The gist of obstetrics,
Springfield,
IL: Charles C. Thomas,
1975, p. 231. 7. Nabors GC: Castor oil as an adjunct to induction of labor: critical reevaluation. Am J Obstet Gynecol 75:36, 1958. 8. Mathie JG, Dawson BH: Effect of castor oil, soap enema, and hot bath on the pregnant human uterus near term: a tocographic study. Brit Med J 1162: May 2, 1959. 9. Bishop EH: Pelvic scoring for elective induction. Obstet Gynec 24266, 1964. 10. Luderer JR, Demers LM, Nomides CT, Hayes AH JR: Mechanism of action of castor oil: a biochemical link to
369
the prostaglandins In: Samuelsson B, Ramwell PW, Paoletti R, eds: Advances in prostaglandin and thromboxane research, vol. 8, New York: Raven Press, 1980, pp. 1633- 1635. 11. Woodward HL, Gardner B: Obstetric management and nursing. Revised by R Bryand and AE Overland. 5th ed. Philadelphia: F. A. Davis Co., 1956, p. 645.
12. Davies DP, Gomersall R, Robertson R, Gray OP, Tumbull AC: Neonatal jaundice and maternal oxytocin infusion. Brit Med J 3:476, 1973. 13. D’Souza SW, Black P, Mac-
370
Farlane T, Richard D: The effects of oxytocin in induced labor on neonatal jaundice. Brit J Obstet Gynaecol 86:133, 1979. 14. Granat M, Borochowitz Z, Berger A, Sharf M: Bilirubin and protein concentration in cord bleed after spontaneous versus induced labor: correlation to neonatal hyperbilirubinemia. J Perk-rat Med 9:27, 1981. 15. Brinsden PRS, Clark AD: Postpartum haemorrhage after induced and spontaneous labour. Brit Med J 2:855, 1978. 16. Yudkin P, Frumar AM, Anderson
Journal
of Nurse-Midwifery
l
ABM, Tumbull AC: A retrospective study of induction of labor. Brit J Obstet Gynaec 841257, 1979. 17. Knutzen VK, Tanneberger U, Davey DA: Complications and outcome of induced labour. S African Med J 10482, 1977. 18. Liston WA, Campbell AJ: Dangers of oxytocin induced labour to fetuses. Brit Med J 3:606, 1974. 19. Thadepalli H, Appleman MD, Chan WM, et al: Amniotic fluid contamination during fetal monitoring. J Reprod Med 20:93, 1978.
Vol. 29, No. 6, November/December
1984
Lorna Davis, CNM,
MSN
ABSTRACT Induction of labor is often necessary in patients with premature rupture of membranes. While the effect of oxytocin to stimulate labor is well established, it is potentially hazardous to both the mother and infant. In this study, castor oil was evaluated as a method to induce labor in uncomplicated patients at term gestation with premature rupture of membranes. A total of 196 patients with premature rupture of membranes was studied retrospectively. Of 107 patients who received castor oil, 75% went into labor as compared to 58% of 89 control patients who went into labor spontaneously (P < 0.02). On the basis of these results, it is concluded that castor oil, which is more economical and convenient than oxytocin, can be used safely and effectively to stimulate labor.
Castor oil was first noted to have oxytocic properties by ancient Egyptians,l and remained a very popular stimulant for the induction of labor until the mid-1950s.2-6 Specific reasons for the decline in the use of castor oil thereafter are not apparent
in the literature. However, it seems likely that the decline was due primarily to the introduction and widespread use of oxytocin. There have been only two clinical trials published on the use of castor oil as a means of inducing labor. In 1958, Nabors7 evaluated the effectiveness of castor oil in combination with pitocin and artificial rupture of membranes. He demonstrated slightly fewer failed inductions in the
*This paper is adapted from a presentation made at the 28th Annual Convention of the AmericanCollegeof Nurse-Midwives,Los Angeles, CA, May 1983. Data obtained from Maternity Center Association, New York, New York. Address correspondence to Lorna Davis, CNM, 250 Mercer Street, New York, NY 10012.
group that was given castor oil, but concluded that castor oil was of no real value in the induction of labor. The subjects in this trial were all highrisk patients; they were not at term gestation, and their cervices were not considered “ripe.” The inductions were considered obligatory because of definite obstetrical indications such as preeclampsia and hypertension. In 1959, Mathie and Dawson8 published a more favorable opinion of castor oil. They measured the contractility of the uterus after the administration of castor oil and demonstrated a marked increase in uterine activity. The authors felt the castor oil could expedite the spontaneous onset of labor or increase the effectiveness of other methods of induction, and they concluded that it should continue to be used for this purpose. The benefit of oxytocin to stimulate labor is well established and is essential in inductions for numerous medical indications. However, it is potentially hazardous to both the inJournal
366 Copyright
0 1984 by the American
College of Nurse-Midwives
of Nurse-Midwifery
l
fant and mother and is neither as convenient nor as economical as castor oil. Observations at this birth center suggested that castor oil could safely stimulate labor, and therefore still had a place in obstetrical practice. This study was designed to evaluate the capability of castor oil to stimulate labor in medically uncomplicated patients at term gestation with premature rupture of membranes (PROM). MATERIALS
AND
METHODS
The data for this study were obtained retrospectively by reviewing all charts of patients admitted to an out-of-hospital
birthing
center
from
1976
through 1981. Maternity care at this center is provided by a team of certified nurse-midwives and obstetricians and is offered to carefully screened low-risk mothers. Some maternal complications that exclude the mother from receiving birth center care include hypertension, diabetes, cardiac disease, anemia, mulVol. 29, No. 6, November/December
1984
0091-2182/84/$03.00
tiple pregnancy, labor onset occurring at less than 37 weeks gestation, nonvertex presentations, meconium staining, and ruptured membranes for longer than 24 hours. If the patient becomes ineligible for care according to the risk criteria, she is transferred to a hospital where one of the birth center’s three obstetricians assumes responsibility for her care. All patients studied had uncomplicated medical and obstetrical histories and singleton, vertex presentations with PROM between 37 and 42 weeks gestation. In this study, the term PROM is used to define the spontaneous rupture of membranes at term gestation occurring before the onset of labor. It was diagnosed on the basis of gross leakage of fluid, ferning, or a positive nitrazine test. Labor was defined as the onset of regular contractions resulting in cervical dilation and effacement. Prior to 1978, the policy at the birth center regarding PROM was to await labor onset without administering any intervention; all women in this group with ruptured membranes became the control group. Subsequently, the medical board approved a policy prescribing that all patients presenting with PROM and a latency period of at least four hours be given 2 oz of castor oil orally. There was no selection process used once this policy changed; this group constituted the experimental group. All patients during this study period, 1976-1981, were observed for labor onset for 24 hours after PROM. If labor did not occur during this
time, the patients were transferred to a hospital for oxytocin stimulation. The longest interval between rupture of membranes and subsequent delivery was 48 hours. The doses of oxytocin required to effect cervical dilation were not available and therefore were not evaluated. In addition to assessing whether castor oil stimulated labor, factors that might have influenced the effectiveness of castor oil were also evaluated. Parity, bishop score (evaluation of the cervix for ripeness), gestational age of patients, and birthweight of the infant were all assessed individually. Bishop scoring was done weekly beginning at 36 weeks; the score evaluated in ths study was the one from the most recent pelvic examination prior to rupture of membranes. Furthermore, the outcomes of the labors in the two study groups were analyzed for method of delivery, need for oxytocin intervention, Apgar scores of the infants, and the presence of meconium. Of 196 patients studied, 107 received castor oil, and 89 did not. Most patients were white, predominantly middle- and upper-class women with a mean age of 28 years. There were 160 primiparas and 36 multiparas. Data were analyzed for statistical significance by a t-test to individually evaluate multiple factors on a single dependent variable.
TABLE
RESULTS
During the years 1976 through 1981, 196 patients between 37 and 42 weeks gestation with ruptured membranes for at least four hours and not in labor were treated at the birth center. There were 160 primiparas, which is reflected in the low Bishop scores (Table 1) and 36 multiparas. The patient characteristics of the two groups are shown in Table 1. The two groups did not differ with respect to patient age, parity, gestational age, or Bishop score. Table 2 demonstrates an association between castor oil administration and an increased frequency of labor onset. In the castor oil group, 80 of 107 patients (75%) had labor onset while only 52 of 89 patients (58%) in the control group had spontaneous labor. This difference is sig-
nificant at P < 0.05. The time from administration of castor oil to onset of labor ranged from 1 to 13 hours, with a mean of 4 hours. Factors that might influence the effectiveness of castor oil were also examined. The significance of parity, Bishop scores, birthweight of the infant, and gestational age appear in Table 2. The effects of castor oil were most pronounced among primiparas; 75% of the experimental group primiparas went into labor compared with the control group in which only 54% of the primiparas had spontaneous labor. This is a significant
1
Patient characteristics Castor
oil
(n = 107) Loma
Davis,
CNM,
MSN
graduated
from
the Saint Louis Univeristy nursemidwifery program in 1978. After working for the Maternity Center Association for three years, she joined a priuate practice Kraus,
practice. She is current/y in in New York City with Nancy CNM, Joanne Monson, CNM, Marcia Starch, MD, Shelley Kolton, MD, and Beth Shimlock, MD.
Control (n = 89)
Factor
Mean
SD
Mean
Age Gravidity No. of term births No. of premature births No. of abortions No. living children Gestational age Bishop score
28.6 1.9 0.2 0.0 0.7 0.2 39. 3.6
7.9 1.2 0.6
27.6 2.0 0.2 0.0 0.9 0.2 39. 3.0
1.0
0.6 1.2 3.9
SD
3.8 1.1 0.4 0.9 0.4 1.3 2.5
Level of significance NS NS NS NS NS NS E
NS, Not significant.
Journal
of Nurse-Midwifery
l
Vol. 29, No. 6, November/December
1984
367
TABLE
2
Patient characteristics
extrapolation of this data to all women, which should be done with caution.
and frequency of labor Castor oil group
Control group
No. in labor/
Level of
No. in labor/ total no.
%
total no.
%
significance
Total no. of patients Patient characteristics Primiparas Multiparas Bishop: O-4 Bishop: 5-9 Birthweight 2100-3099 g Birthweight 3100-3900 g Birthweight 3901-4999 g
80/107
74.8
52189
58.4
P < 0.05
66188 14/19
75.0 73.7
46164
71.9
31/40 13/19
39172 13/17 35163 17126
68.4
12/19
80.6 68.4
31/48 418
54.2 76.5 55.6 65.4 63.2 64.6 50.0
P < 0.01 NS NS NS NS NS NS
Weeks gestation 39-40 37-38 Weeks gestation 41-42
48164 19125
76.0 75.0 72.2
32145 18130 2114
60.0 71.1 14.3
E P < 0.01
54167 13/19 13/18
77.5
NS, Not significant.
finding, with P < 0.01 (Table 2). Castor oil was significantly associated with onset of labor at gestational ages 41-42 weeks (P < 0.01). The incidence of labor within 24 hours in the castor oil group and the control group was not significantly different for multiparas, Bishop score categories, birthweight distributions, and gestational ages 37-40. In addition to examining factors that may influence the effect of castor oil, labor outcomes were also evaluated for type of delivery, incidence of oxytocin stimulation, and infant wellbeing, as evidenced by Apgar scores and presence of meconium. There were nearly three times as many cesarean sections in the control group (15.7%) compared to the castor oil group (5.6%), percentages that differ significantly, P < 0.01. The castor oil group did not require oxytocin stimulation (36%) as frequently as did the control group (43%), but the difference was not significant. Of the 38 patients in the castor oil group who needed oxytocin stimulation, 27 were patients who did not have any contractions after the administration of castor oil and another 11 were patients who had contractions that were inadequate to cause cervical dilation. This compares with 37 patients in the
control group who did not go into labor and one patient who had inadequate contractions. Infant outcomes were examined in the two groups by noting Apgar scores at one and five minutes and by determining whether meconium staining was present. There were two infants in both groups with Apgar scores less than seven at one minute and the two in the control group remained less than seven at five minutes. The presence of meconium at the time of rupture of membranes in the two groups was very low, and no one developed meconium staining after the administration of castor oil. In addition to the good infant outcomes, there was no significant maternal morbidity and no maternal deaths. The expected side effect of castor oil, diarrhea, did occur in almost everyone; however, maternal dehydration and electrolyte imbalance were not problematic. Limitations
of the Study
A limitation of this study is the lack of randomization and, therefore, the potential problem of bias and dissimilar groups. In addition, this unique population of women who sought out-of-hospital maternity care limits
Journal
of Nurse-Midwifery
l
COMMENT
These data indicate that patients at term gestation presenting with PROM benefit from the administration of castor oil by stimulating labor. These findings support the clinical observations made at the birth center and are consistent with the research of Mathie and Dawson* in which they reported a marked increase in the contractility of the uterus after the administration of castor oil. Currently, there is no information on the mechanism by which castor oil acts to stimulate contractions. It is thought to work by causing violent intestinal peristalsis, which, by some means, excites the uterus. Luderer et allo in 1980 reported on the mechanism of action of castor oil. They documented by in vivo studies on rats a significant increase in portal venous prostaglandin E concentration after the oral administration of castor oil. The authors concluded that castor oil may induce its cathartic effects by serving as exogenous substrate for intestinal prostaglandin synthesis It may be that there is a relationship between intestinal prostaglandin synthesis produced by castor oil and its effect on the uterus. Patients who took castor oil went into labor more frequently than patients in the control group. However, the effectiveness of the contractions produced by castor oil to accomplish cervical dilation needs further evaluation. In the 80 patients who labored with castor oil, 11 had uterine contractions that were inadequate to dilate the cervix and the patients required further stimulation with oxytocin. There was only one patient in the group who had spontaneous labor that needed further stimulation by oxytocin. This suggests that castor oil stimulated labors may not be as effective as spontaneous labors.
Vol. 29, No. 6, November/December
1984
Parity, Bishop score, birthweight of the infants, and gestational age were factors evaluated individually for their influence on castor oil and spontaneous labor. Among primiparas, the castor oil group had a 75% onset of labor, whereas the control group had a spontaneous labor rate of 58%. Surprisingly, this labor difference was not true among multiparas, primarily due to a high spontaneous labor rate of 77%. The state of the cervix has been shown to relate to successful induction of labor.g Bishop scores of the patients in this study were all less than nine and did not have a significant influence on the effect of castor oil. Birthweight of the infants also did not have an effect on castor oil to stimulate labor. Postdatism is a factor that did appear to produce a significant difference, as seen in the 41-42 week gestational age group. Only 2 of 14 patients in this group went into labor spontaneously, compared with 13 of 18 patients in the castor oil group. This low spontaneous labor rate was unexpected and the explanation for this significant difference is not apparent. The need for oxytocin stimulation and the incidence of cesarean sections were examined in the control group and the castor oil group. Although there was a higher incidence of oxytocin stimulation in the control group, it was not significant. More importantly though, the group who received castor oil had significantly fewer cesarean sections. All patients in both groups who had a cesarean section first received a trial of oxytocin stimulation. The indications for cesarean section were cephalopelvic disproportion (2 patients) and failure to progress (18 patients). Individual practitioner judgment could not be well controlled, but the physicians who made the decisions to perform the cesarean sections remained constant throughout the five-year study period. One theory to explain the low cesarean section rate in the castor oil group is that castor oil may
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ripen the cervix, resulting in fewer failed inductions, and therefore fewer cesarean sections as noted by Nabors’ study7 in 1958. There was no maternal or fetal morbidity in either group. There was one suggestion in the literature that meconium staining occurred after the administration of castor oil.‘l However, no one in this study developed meconium-stained amniotic fluid after the administration of castor oil. There are many disadvantages of oxytocin intervention when compared with the convenience, safety, and cost-effectiveness of castor oil. Neonatal jaundice is often cited as a problem in infants after oxytocin stimulation. 12,13 Granat et al. l4 in 1981 demonstrated an association between the mean total dose of oxytocin used for induction and the incidence of byperbilirubinemia. Brinsden and ClarkI in 1978 documented an increased risk of maternal postpartum hemorrhage after oxytocin stimulation. There have been several authors reporting an increased incidence of operative deliveries with the use of oxytocin.16x17 Oxytocin stimulation requires hospitalization and the attention of specially trained personnel. The patient must be confined to bed due to maternal and fetal monitoring, which is essential with oxytocin stimulation. Bimanual examinations are necessary to monitor progress and for the insertion of fetal electrodes and internal pressure catheters, which are often necessary for accurate monitoring. Many studies indicate an increased risk of fetal infection, amnionitis, and endometritis in those patients who recieve internal monitoring. 18,1g In this study everyone who received oxytocin stimulation also required analgesics. There were only five patients who required analgesics in the group that did not get oxytocin. All analgesics carry some risk to the mother and infant and may result in additional cost. When considering the potential hazards of oxytocin, the inconve-
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nience to the patient and physician, the added expense, and the increased likelihood of a cesarean section, the conservative approach of first using castor oil in patients with PROM seems quite justified. In view of these facts, it is recommended in low-risk populations with PROM that 1) there be an appropriate waiting period for spontaneous labor, 2) if no labor occurs, dispense orally 2 oz of castor oil, and 3) if no labor occurs within 13 hours after the administration of castor oil, oxytocin stimulation should be considered.
This paper is dedicatedto the former nursemidwiferyprogram at Saint Louis University.
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