Abstract
Introduction
Induction of labor is one of the most common obstetrical procedures today, with a successively rising rate. With a limited number of hospital beds, the option of starting induction at home has gained increasing attention. The primary aim of this study was to compare the proportion of women achieving vaginal delivery and the duration of hospital stay before delivery in induction of labor with oral misoprostol starting at home and induction with oral misoprostol at the hospital, in a low‐risk population.
Material and methods
Women with home induction (n = 282) were individually matched to controls induced at the hospital during the same time period regarding parity, age, body mass index, labor unit and indication for induction.
Results
The rates of vaginal birth were similar in outpatients and inpatients (84.8% vs 86.2%; p = 0.5). Time from hospital admission to delivery in the outpatient group was significantly shorter than in the inpatient group (12.8 vs 20.6 h; p < 0.001), as was total hospital stay (2 vs 3 days; p < 0.001). There were no significant differences between the groups in neonatal or maternal outcomes. One patient undergoing outpatient induction had an unplanned home birth.
Conclusions
Starting induction at home reduced the time spent in hospital without affecting the vaginal delivery rate. Although underpowered to assess safety, this study did not show any differences in adverse maternal and perinatal outcomes between inpatients and outpatients. Further research is needed to evaluate the safety of outpatient induction of labor with misoprostol.
Keywords: cervical ripening, misoprostol, outpatient induction of labor, prostaglandins
Induction of labor rates are rising yearly and globally taking up labor resources. A retrospective study was conducted with 282 women in each group induced with oral misoprostol comparing inpatient vs outpatient induction of labor. Outpatient induction of labor had a shorter admission to delivery time and shorter total hospital stay, with similar vaginal delivery rates.
Abbreviations
- BMI
body mass index
- IOL
induction of labor
- NICU
neonatal intensive care unit
Key message.
Outpatient induction of labor is a compelling alternative regarding the rising induction rates worldwide. Results from our study show a shorter time from admission to delivery without affecting the cesarean section rate. Prospective studies are needed to show further benefit.
1. INTRODUCTION
Induction of labor (IOL) has increased from 19% of births in Sweden 2018 to 25% of births in 2020, primarily due to a policy change in prolonged pregnancy (41 + 0 weeks). 1 IOL is defined as the induction of labor by artificially stimulating uterine contractions and cervical ripening by medical or mechanical means before a spontaneous start of labor. 2 , 3 , 4 Misoprostol, a prostaglandin E1 analogue that was initially used for treatment of gastric ulcers, has been used widely off‐label for termination of pregnancy, postpartum hemorrhage and IOL. Angusta® (Misoprostol, Norgine A/S, Netherlands) is the first misoprostol preparation approved in Sweden for IOL. The standard regimen is 25 μg orally every 2 h, since low‐dosage misoprostol induction has been associated with the most favorable outcomes. 5 , 6 , 7
With an increasing number of labor inductions, interest in performing cervical ripening and IOL in an outpatient setting has increased. 1 , 2 , 8 , 9 IOL, especially for primiparas with an unfavorable cervix, can take a substantial amount of time, ranging from hours to days. Undergoing cervical ripening at home is an attractive option to reduce potentially the duration of antenatal hospital stay, reduce strain on healthcare resources, increase satisfaction and comfort for patients, and to reduce financial costs. 8 , 10 , 11 , 12 , 13 , 14 , 15 Currently, there is limited evidence for IOL with oral misoprostol in an outpatient setting. 2 , 6 , 9 , 14
The primary aims of this study were to compare the rates of vaginal delivery and duration of hospital stay before delivery between outpatient and inpatient IOL. Secondary aims were to compare total hospital stay, total dose of misoprostol given, maternal and neonatal safety outcomes.
2. MATERIAL AND METHODS
This is a retrospective study comparing the outcome of IOL with misoprostol starting at home with IOL in the hospital in low‐risk pregnancies between January 1, 2019 and February 1, 2022 at Skåne University Hospital in Lund and Malmö, Sweden.
2.1. Population
The studied population included low‐risk term and post‐term pregnant women with an unripe cervix, defined as a Bishop score ≤5, receiving oral misoprostol for cervical ripening and IOL. Outpatient induction was offered to women who were to be induced for prolonged pregnancy, a suspected large‐for‐gestational age fetus or for humanitarian reasons, meeting none of the exclusion criteria presented in Table 1. In this study, low risk is defined by these criteria. Outpatient induction was offered in Lund from May 2019 and in Malmö from December 2020. Skåne University hospital is a tertiary clinic that also is the primary obstetric hospital for women living in the area. This area is geographically limited; practically everyone can reach the hospital within 30 min by car.
TABLE 1.
Inclusion and exclusion criteria.
| Inclusion criteria |
| Induction of labor with misoprostol for one of the following indications; |
| Prolonged pregnancy (≥41 + 0 weeks) or post‐term pregnancy (≥42 + 0 weeks) |
| Suspected large‐for‐gestational age fetus (estimated birthweight > 2 SD for gestational age) |
| Humanitarian reason |
| Exclusion criteria |
| Preterm gestation (<37 + 0 gestational weeks) |
| Intrauterine growth restriction (estimated birthweight < –2 SD below mean for gestational age or relative decrease in estimated birthweight for gestational weight by 10 percentiles). |
| Abnormal fetal blood flow measurement |
| Decreased fetal movements |
|
Hypertension (systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg at two measurements with at least 4 h apart) Preeclampsia (onset of hypertension and significant end‐organ dysfunction or proteinuria after 20 weeks of gestation) |
| Pregestational diabetes, insulin‐ or metformin‐treated gestational diabetes |
| Abnormal CTG pattern |
| Uterine bleeding during the 3rd trimester |
| Oligohydramnios (AFI <50 mm) |
| Polyhydramnios (AFI >250 mm) |
| Unstable fetal lie |
| Twin pregnancy |
| Primipara ≥40 years of age |
| BMI >35 kg/m2 |
| Egg donation |
| Cholestasis of pregnancy |
| Previous cesarean section |
| Country of birth in Africa south of Sahara |
| Mature cervix (Bishop score >5) |
| Rupture of membranes before induction start |
|
Spontaneous start of contractions before induction start |
Abbreviation: AFI, amniotic fluid index.
2.2. Study groups
The outpatient study group included all women fulfilling the specified criteria for outpatient induction (Table 1) who started IOL at home. The comparison group included women with IOL with misoprostol in the hospital during the same period, fulfilling the same criteria. The comparison group was selected using the computerized registry of deliveries. The comparison group was constituted by including, for each outpatient IOL, the first patient with misoprostol IOL in the hospital fulfilling the criteria in Table 1, with matching labor unit (Lund, Malmö), body mass index (BMI) group (<25, 25–30, 30–35), age group (<25, 25–35, >35), parity (primipara vs multipara) and indication for IOL.
2.3. Protocol for outpatient IOL with misoprostol
Women eligible for outpatient IOL underwent a vaginal examination, blood pressure measurement and fetal heart rate assessment by cardiotocography. An ultrasound was performed to measure the amniotic fluid index and to ascertain the fetal presentation. Patients who were deemed eligible for outpatient IOL by the obstetrician on duty were given oral and written information regarding outpatient IOL. Upon accepting the offered regimen, they received 5 tablets of Angusta® 25 μg to take according to the following schedule: 25 μg at 6 pm, 8 pm and 10 pm, and after an overnight sleep at home, 25 μg at 6 am and 8 am. Patients were told to call the midwife on‐call if they experienced contractions, rupture of membranes, bleeding or decreased fetal movements and would then be advised to return to the hospital for a clinical examination and admission to the hospital if needed. Patients were readmitted at 9 am next day, for another vaginal examination and cardiotocography. If everything was in order, and the patient was not in active labor, she returned home with four more doses of misoprostol to be taken at 10 am, noon, 2 pm and 4 pm. The patient was told to return to the maternity ward at 5 pm, where she would remain until having given birth. If the cervix was still unripe and the patient not in labor, she would be given 50 μg misoprostol at 6 pm. If a secondary method of induction was needed thereafter, a balloon catheter was the preferred method if the cervix was dilated <3 cm and amniotomy if the dilation was ≥3 cm.
2.4. Protocol for hospital induction with misoprostol
During the study period, the protocol for inpatient hospital induction was using low‐dose oral misoprostol in solution. A tablet of 200 μg misoprostol (Cytotec®, Pfizer AB, USA) was dissolved in 100 mL of tap water. The patient was given 20 mL (40 μg) of oral misoprostol solution every second hour until active labor or cervical dilation to 3 cm or more was achieved, up to a maximum of 12 doses. During 2019–2020 the first two doses given were limited to 20 μg. Balloon catheter was recommended as a secondary method when additional cervical ripening was needed. During 2019–2020 this was not considered until 12 doses of misoprostol had been given, whereas in the protocol thereafter, catheter was recommended to be considered after four to six doses of misoprostol.
Since this was a retrospective study, we compared outpatient and inpatient inductions with misoprostol with current clinical protocols described above. The protocols mainly differed in dosage (25 μg tablets every 2nd hour in outpatient inductions, and 40 μg in oral solution every 2nd hour in inpatient inductions), and in that outpatient inductions started at 6 pm with an 8‐h overnight pause between dose 3 and 4, whereas inpatient inductions could start at any time (usually 10 am to 6 pm) and were not paused during the night.
2.5. Outcome variables
The primary outcome variable was the rate of vaginal delivery and duration of hospital stay before delivery. Secondary outcome variables to assess efficacy were: induction to delivery interval, time from 5 cm cervical dilation until birth, total duration of hospital stay, total dose of misoprostol, need for additional induction methods, and augmentation of labor with oxytocin. Secondary outcomes to assess safety were Apgar score <7 at 5 min, umbilical cord pH below 7.10, admission to the neonatal intensive care unit, perinatal mortality, cesarean delivery for fetal distress, postpartum hemorrhage ≥1000 mL, obstetric anal sphincter injury and postpartum maternal infection requiring antibiotic treatment.
2.6. Data collection
Information regarding the unit for giving birth, date of giving birth, induction setting (inpatient vs outpatient), the patient's date of birth, BMI, parity, fetal presentation, Apgar at 1, 5 and 10 min, umbilical cord arterial and venous pH at birth, admissions to neonatal intensive care unit and diagnose codes from International Classification of Diseases Tenth Revision (ICD‐10) were retrieved from the computerized patient charts. The study group of outpatient inductions was retrieved by review of the delivery register and perinatal records in the patient charts of all women that had an assigned diagnostic code used for outpatient IOL (ICD‐10: DM002). Remaining data were retrieved by reading the patient charts. The Bishop score was determined according to Wormer et al. 16 The induction to delivery interval was calculated from the time of receiving the first dose of misoprostol until delivery. The women in the outpatient group were given written information on exact time points on when to take the medication and contact information on how to reach the labor ward when needed. Upon arriving to the labor ward, the women in the outpatient group reported in written form the times when the tablets were taken and returned any remaining tablets (if any) to the staff.
2.7. Statistical analyses
The number of available outpatient inductions to study was limited to 282, as well as the number of comparisons in hospital inductions matching the inclusion criteria. Therefore, no power analysis was performed before the study to assess the sample size.
All data were analyzed using the statistical program IBM SPSS Statistics for MAC version 27 (SPSS Inc.). Pearson's chi‐square test was used for categorical outcomes, and Student's t‐test and Mann–Whitney U tests for continuous data. To determine whether the data were normally distributed, the Shapiro–Wilk test was used (alpha = 0.05). Relative risks with 95% confidence intervals were calculated for the primary outcome of cesarean delivery. Differences were considered statistically significant at the 0.05 level.
2.8. Ethics statement
This study was approved on March 28, 2022 by the Swedish Ethical Review Authority (file record: 2022–01331‐02).
3. RESULTS
Between January 1, 2019 and February 1, 2022, labor was induced for 4593 women at Skåne University Hospital. The study includes 282 women who were induced in an outpatient setting and 282 women induced in a hospital setting.
Due to the matching of outpatients and inpatients, the baseline characteristics of women in these groups were comparable with respect to age, parity, BMI and IOL indication (Table 2). Bishop score was not matched for but did not differ significantly between the two groups.
TABLE 2.
Baseline characteristics.
| Outpatient group, n = 282 | Inpatient group, n = 282 | |
|---|---|---|
| Nulliparous, n (%) | 190 (67.4) | 190 (67.4) |
| Age, years, median (IQR) | 31 (5) | 30 (6) |
| BMI, median (IQR) | 24.9 (5.9) | 24.9 (5.9) |
| Gestation at IOL, days, median (IQR) | 288 (9) | 288 (11) |
| Bishop score at induction start, median (IQR) | 2 (3) | 3 (3) |
| IOL indication | ||
| Prolonged pregnancy, n (%) | 180 (63.8) | 180 (63.8) |
| Humanitarian/elective, n (%) | 62 (22) | 61 (21.6) |
| Suspected fetal macrosomia, n (%) | 39 (13.8) | 40 (14.2) |
| Gestational diabetes, n (%) | 1 (0.4) | 1 (0.4) |
3.1. Primary outcomes
The rates of cesarean delivery were similar in outpatients and inpatients (15.2% vs 13.8%; relative risk 1.12 (95% CI, 0.75–1.6); p = 0.5). The time spent at the hospital before giving birth was significantly shorter in the outpatient group than in inpatients (12.8 vs 20.6 h; p < 0.001).
3.2. Secondary outcomes
More women in the inpatient group than in the outpatient group received secondary methods of induction (balloon catheter or dinoprostone) (33.3% vs 25.5%; p = 0.042). By contrast, more women in the outpatient group received oxytocin infusion for augmentation of labor (65% vs 52%, p = 0.003). Women with outpatient IOL remained at home for a mean period of 17 h from the first dose of misoprostol. The total hospital stay was shorter for women who were induced as outpatients (2 vs 3 days; p < 0.001). Time from induction to delivery was longer for outpatient than for inpatient inductions (30.3 vs 20.6 h; p < 0.001). The duration of labor from 5 cm cervical dilation to delivery was longer in the outpatient group than in the inpatient group (5.7 vs 4.3 h; p < 0.001).
No neonatal or maternal outcomes differed significantly between the two study groups (Table 3). Fifteen neonates in the outpatient group and 10 in the inpatient group were admitted to neonatal intensive care unit (NS). Four of these newborns met criteria for light‐grade asphyxia; two from the outpatient group and two from the inpatient group. All were delivered instrumentally. Three of these infants had 5‐min Apgar scores <7 at 5 min and had arterial umbilical cord pH between 7.05 and 7.09. One infant had metabolic acidosis (pH <7.05 and base deficit >12 mmol/L). There was no case of perinatal mortality in the study. One patient undergoing outpatient induction had an unplanned home birth.
TABLE 3.
Primary and secondary outcomes.
| Outpatient group n = 282 | Inpatient group n = 282 | p‐value | |
|---|---|---|---|
| Primary outcomes | |||
| Vaginal delivery, n (%) | 238 (84.4) | 243 (86.2) | 0.55 |
| Duration from hospital admission to delivery, hours, median (IQR) | 12.8 (14.4) | 20.7 (17.1) | <0.001 |
| Secondary outcomes | |||
| Cesarean delivery for fetal distress, n (%) | 15 (5.3) | 16 (5.7) | 0.52 |
| Cesarean delivery for dystocia, failed induction or maternal exhaustion, n (%) | 26 (9.2) | 21 (7.4) | 0.63 |
| Instrumental delivery for fetal distress, n (%) | 17 (6.0) | 19 (6.7) | 0.64 |
| Instrumental delivery for dystocia or maternal exhaustion, n (%) | 11 (3.9) | 17 (6.0) | 0.45 |
| Additional method of cervical ripening n (%) | 72 (25.5) | 94 (33.3) | 0.42 |
| Dinoprostone | 16 (5.7) | 59 (20.9) | <0.001 |
| Balloon catheter | 58 (20.6) | 45 (16.0) | 0.16 |
| Amniotomy | 157 (55.7) | 149 (52.8) | 0.50 |
| Oxytocin infusion | 184 (65.2) | 149 (52.8) | 0.003 |
| Total hospital stay, days, median (IQR) | 2 (2) | 3 (2) | <0.001 |
| Total dose misoprostol, μg, mean rank (IQR) | 253 (175) | 297 (120) | <0.001 |
| Induction start to birth, hours, median (IQR) | 30.4 (19.2) | 20.7 (17.1) | <0.001 |
| Apgar score <7 at 5 min n (%) | 3 (1.1) | 3 (1.1) | 0.99 |
| Umbilical artery cord pH <7.10, n (%) a | 8 (4.8) | 8 (4.8) | 0.99 |
| Admission to NICU, n (%) | 15 (5.3) | 10 (3.5) | 0.31 |
| Postpartum hemorrhage >1000 mL, n (%) b | 31 (11.3) | 234 (12.1) | 0.77 |
| Postpartum infection, n (%) | 6 (2.1) | 5 (1.8) | 0.76 |
| Perineal tears grade 3–4 | 9 (3.28) | 13 (4.6) | 0.38 |
Total number with analysis of cord artery pH: 166 outpatients and 167 inpatients.
Total number with documented blood loss: 275 outpatients and 275 inpatients.
3.3. Subgroup analyses
The duration of hospital stay before birth was shorter in outpatient inductions than in hospital inductions, and the rate of vaginal birth was similar in outpatient and inpatient IOL in primiparous as well as in parous women, and in women with a Bishop score 0–2 as well as in those with score 3–5 at induction start (Table 3).
4. DISCUSSION
The main findings of this study were that induction with misoprostol in an outpatient setting resulted in a similar rate of vaginal delivery as in IOL with misoprostol at the hospital, whereas the time spent in hospital from admission to delivery was significantly reduced.
To our knowledge, this is the first study to compare 2‐h oral low‐dosage misoprostol in an outpatient setting compared with in an inpatient setting. Our results are consistent with two available studies using single doses of misoprostol for outpatient cervical ripening. Kandahari et al. conducted a retrospective cohort study of 345 women undergoing cervical ripening as an outpatient regimen. 17 Roloff et al. conducted a retrospective cohort study comparing 56 women induced as outpatients with matching controls induced as inpatients. 18 Both studies showed shorter time from admission to delivery with outpatient start of induction and no significant differences in delivery outcomes compared with an inpatient group.
Studies of outpatient induction with a Foley catheter or prostaglandin E2 have also shown reduction in time at the hospital, 8 , 19 , 20 with no significant differences in maternal or neonatal outcomes. None of these studies showed any significant difference in cesarean delivery rates, but the studies were underpowered to compare this outcome. However, a 2020 meta‐analysis of outpatient compared with inpatient IOL with balloon catheter showed a significantly reduced rate of cesarean section. 19 Our study did not show a difference in cesarean section rate with outpatient and inpatient IOL.
A Dutch multicenter randomized control trial indicated that oral misoprostol had similar safety and effectiveness to Foley catheter for IOL. 3 A previous study on low‐dose misoprostol (25 μg) in comparison with high‐dose misoprostol (50 μg) in inpatient IOL showed that low‐dose induction was associated with an increased probability of vaginal delivery but a higher risk of instrumental delivery. A decrease in neonatal intensive care unit admissions was noted in the low‐dosage misoprostol group. 5
A limitation of our study was that the protocols for home induction and hospital induction were not identical. The outpatient IOL protocol included an overnight sleep with 8 h without misoprostol administration, whereas the inpatient IOL protocol had no pause during the night, and the misoprostol doses in inpatient induction (40 μg) were higher than the doses (25 μg) in outpatient induction. The reason for this was that patients induced at home cannot be monitored as closely as inpatient IOL and therefore receive a lower dose of misoprostol in a 24‐h timespan. The different protocols may have resulted in differences not associated with the actual setting of the IOL or may have masked differences due to setting. The finding that the time interval from start of induction to delivery was 10 h longer in the outpatient group is probably explained by this difference in protocol.
Another limitation is that the included number of patients does not allow conclusions about safety. Although there were no differences in neonatal or maternal outcomes, our study was not powered to compare safety outcomes.
In this study we matched patients induced at the hospital for the risk criteria applied for home induction, as well as for BMI, age, parity, indication of induction and site of giving birth. Still, with a retrospective design we cannot exclude undisclosed confounders. Thus, it cannot be ruled out that patients with risk factors not included in the protocol may have been recommended hospital IOL rather than outpatient IOL.
The inpatient group had a nonsignificantly higher median Bishop score at the start of induction. We do not consider the differences in Bishop score at induction start to affect the main outcomes since the rates of vaginal delivery were similar in the study groups, and the duration of hospital stay was shorter in outpatient IOL even when stratified by Bishop score (Table 4).
TABLE 4.
Primary outcomes stratified by parity and Bishop score at induction start.
| Outpatient group | Inpatient group | p‐value | |
|---|---|---|---|
| Primipara | n = 190 | n = 190 | |
| Vaginal delivery, n (%) | 148 (77.9) | 153 (80.5) | 0.53 |
| Duration from hospital admission to delivery, hours, median (IQR) | 15.5 (12.8) | 25.5 (18.0) | <0.001 |
| Multipara | n = 92 | n = 92 | |
| Vaginal delivery, n (%) | 90 (97.8) | 90 (97.8) | 1.0 |
| Duration from hospital admission to delivery, hours, median (IQR) | 7.1 (8.2) | 13.4 (11.5) | <0.001 |
| Bishop score 0–2 | n = 139 | n = 122 | |
| Vaginal delivery, n (%) | 109 (78.4) | 95 (77.9) | 0.48 |
| Duration from hospital admission to delivery, hours, median (IQR) | 15.8 (15.2) | 27.1 (20.8) | <0.001 |
| Bishop score 3–5 | n = 136 | n = 156 | |
| Vaginal delivery, n (%) | 122 (89.7) | 148 (94.9) | 0.14 |
| Duration from hospital admission to delivery, hours, median (IQR) | 10.5 (12.1) | 17.6 (13.8) | <0.001 |
Women with outpatient IOL stayed 1 day less at the hospital than those induced as inpatients. With a limited number of hospital beds and a high rate of IOL, this difference may have important implications for availability of care and costs. Three studies assessing cost‐saving in outpatient cervical ripening found that outpatient IOL saved between US $156 and US $550 per patient, though the differences were statistically significant. Overall outpatient cervical ripening seems to be cost effective, as it decreases the overall costs associated with prolonged hospitalization. 10 , 13 , 22
In the present study, we have no data to compare maternal satisfaction in inpatient and outpatient IOL. Two previous studies support outpatient cervical ripening/IOL in terms of achieving a greater patient satisfaction, 14 , 23 whereas one study in parous women found no difference in satisfaction in women undergoing inpatient and outpatient cervical ripening. 12
5. CONCLUSION
This retrospective study showed that outpatient induction with misoprostol reduced the time needed in hospital before delivery and total hospital stay, whereas the rate of vaginal birth was similar to that in inpatient IOL. Maternal and neonatal outcomes did not differ between outpatient and inpatient inductions but larger studies are needed to evaluate the safety of outpatient IOL with misoprostol.
AUTHOR CONTRIBUTIONS
NH, MA, DW‐S and AH conceived the study. NH conducted data collection and analysis with support from MA and AH. NH wrote the paper with support from MA, AH and DW‐S. All authors contributed to the article and approved the submitted version.
CONFLICT OF INTERESTS STATEMENT
The authors have stated explicitly that there are no conflicts of interest in connection with this article.
Hallén N, Amini M, Wide‐Swensson D, Herbst A. Outpatient vs inpatient induction of labor with oral misoprostol: A retrospective study. Acta Obstet Gynecol Scand. 2023;102:605‐611. doi: 10.1111/aogs.14550
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