According to The American College of Obstetrician and Gynaecologists (ACOG) Misoprostol as a vaginal insert is recommended to use to induce labor in pregnant women . It is proven to be a reliable and safe method to support cervical ripening . Unfortunately, since the end of 2019 it is no longer available in Germany.
A rather large and sensitive group of pregnant women are women with pregnancies beyond 40 + 0 weeks of gestation. In addition to their already existing risk factors the likelihood for placental insufficiency is even higher in this cohort . A Cochrane database by Middleton et al. was able to show an association between induction of labor and fewer stillbirths for women carrying pregnancies beyond 41 weeks . But at the same time in day-to-day clinic these women often need or even ask for induction of labor. However, there were only few data regarding this patient group .
To our knowledge this is the first study to focus on women with pregnancies beyond 40 + 0 weeks only. We demonstrated that Misoprostol as a vaginal insert for induction of labor in 304 women with pregnancies beyond their expected date of birth is efficient and safe.
More than 75% of women who were induced achieved vaginal birth within 24 hours. In this specific cohort with increased risks we found no higher rate of caesarean deliveries. In comparable studies for preterm induction of labor the rates in CS delivery mode were reported as 16.6–32% [8, 20]. In our cohort with a median duration of 40 + 6 weeks the rate of CS was 32.0%. This comparably high deliveries emphasize the increasing risk of fetal distress in prolonged pregnancies.
Until now literature is still controversial when it comes to the rates of caesarean deliveries and fetal outcomes after the Induction with MVI. Some research indicates significantly higher caesarean section rate and negative effects on fetal outcome . Sharp et al (2019) demonstrated increasing caesarean deliveries comparing MVI with dinoprostone intravaginal gel. Other studies were able to show that there is no difference in perinatal outcome, rates of CS and vaginal operative delivery comparing MVI to oral misoprostone or dinoprostone insert [9, 11, 12, 15, 21].
For safety aspects, our group of women with pregnancies beyond 40 + 0 weeks is a high-risk population due to potential placental insufficiency during labor, which could cause fetal distress leading to unfavourable outcomes . Gulmezoglu et al. summarized in a Cochrane database review that risks for mothers and their unborn babies start to increase significantly after 41 + 0 weeks . Risks for meconium aspiration, caesarean delivery and perinatal morbidity start to increase significantly.
This study is mainly limited by two factors: its monocentric and single-arm design. Furthermore, this prospective trial could have had an increased value if we would have had a randomized design contrasting for example misoprostol vaginal insert with dinoprostol vaginal insert or other methods of application. In addition, a higher statistical power could be achieved with a larger cohort.
Regarding to the manufacturer’s guidelines MVI is supposed to be removed at the onset of labor or after 24 hours at the latest. Catching the exact moment of onset of labor seems to be crucial to avoid hyperstimulation, although in clinical everyday it is sometimes impossible to intervene at the ideal moment. After 12 hours misoprostol vaginal insert released 50% of its effective dose. It´s biological half-life is 45 minutes. We decided to remove MVI after 12 hours at the latest to lower the risk of hyperstimulation.
Hyperstimulation after induction with misoprostol vaginal insert is a common side effect. Women who receive MVI and healthcare professionals who take care of those need to be aware of this fact. We suggest hospitalisation of women who receive MVI to ensure that they are monitored thoroughly so that in case of hyperstimulation or fetal distress midwives and responsible doctors have the chance to take care of the situation to ensure safety for mothers and their unborn babies. With this approach we were able to avoid hyperstimulation in most cases which is reflected by the use of tocolysis for approximately 10% only.
When deciding which method to choose for induction of labor there is need for an informed decision making. MVI is a very efficient and a fast method to achieve vaginal birth due to its controlled release system. Risks for hyperstimulation and need for a rapid birth need to be carefully balanced out. Women need to be informed about benefits and potential risks to be able to make informed choices. Looking at our data we strongly support further use of MVI to induce labor. From our clinical under clinical aspects the withdrawal of Misodel™ is not comprehensible.