Labor induction at term and beyond : Effects on vaginal delivery rate, adverse outcomes, and childbirth experiences

One in three labors in Finland is induced. Compared with spontaneously initiated labor, induced labor increases the risk of cesarean section (CS) and a negative childbirth experience. Waiting for a spontaneous onset of labor is not always feasible, however, and labor induction may be needed to protect maternal or fetal health. When labor induction is compared with expectant management, the associations with CS rates and childbirth experiences may differ. This thesis explores how labor induction affects CS rates and adverse outcomes in women in light of the common pre-labor risk factors of prior CS for labor dystocia or failed labor induction, group B streptococcus (GBS) colonization, nulliparity, and late- or post-term pregnancy. This thesis also aims to discover ways to ameliorate the childbirth experience in women who undergo labor induction. Five original articles form the basis of this thesis. Two of the articles detail retrospective cohort studies (I and II), and two are about a single prospective cohort study (III–IV). Study V (submitted) describes a randomized controlled multicenter trial. Study I showed that 72.9% of women who had previously undergone a CS for labor dystocia or failed labor induction succeeded in a trial of vaginal delivery. Traditional risk factors for CS, such as labor induction and a lack of prior vaginal delivery, were also identified as risk factors in our study. The rate of repeat CS was twofold in women with a prior failed labor induction (41.0%) compared with women who had previously experienced labor dystocia in the first (24.4%) or second stage of labor (26.9%, p = 0.003). The greatest rate of CS, 48.1%, was found in women with a history of prior failed labor induction who underwent labor induction in their current pregnancy. Study II showed that, in terms of infection, labor induction by balloon catheter was safe in GBS-positive women with intact membranes when prophylactic antibiotics were administered at the onset of labor or membrane rupture. In our study, the rate of maternal intrapartum infection was lower in GBS-positive women than in GBS-negative women, at 4.7% vs. 8.3% (p = 0.01). The rates of maternal postpartum infection and neonatal infection were similar in the two groups. A prolonged duration of ruptured membranes (≥ 12 hours) was associated with all types of infection assessed. Studies III and IV showed that women who underwent labor induction had relatively positive childbirth experiences. The negative experiences of women with their first birth were mainly associated with the same delivery-related factors that affected the parous women: CS and hemorrhage. The nulliparous women, however, scored lower on assessments of their own capability to give birth. Thus, the confidence and agency of such women should be enhanced through antenatal education. The choice of labor induction method—balloon catheter or misoprostol—had no effect on childbirth experiences, but women treated with balloon catheters were more content with the method chosen and stated that they would choose the same method in a future pregnancy. Study V identified a reduced rate of operative delivery in nulliparous women with unripe cervices if they underwent labor induction at 41+0 gestational weeks compared with expectant management and labor induction at 41+5 to 42+1 gestational weeks (30.6% vs. 45.6%, p = 0.003). The rates of CS (16.7% vs. 24.1%, p = 0.07) and adverse neonatal outcomes (9.7% vs. 14.4%, p = 0.16) did not differ between the groups, and no perinatal deaths occurred. Of the women who completed a vaginal delivery, the rates of operative delivery by vacuum extraction were lower in the early induction group than in the expectant management group (16.8% vs. 28.4%, p = 0.02). In addition, fewer women in the early induction group had hemorrhage ≥ 1,000 ml (12.2% vs. 20.8%, p = 0.03). Of the women who had been through expectant management, 45.6% had a spontaneous onset of labor. In conclusion, offering a trial of labor after CS to women with a history of prior CS for labor dystocia or failed labor induction may be encouraged, although a failed labor induction in the prior pregnancy or the need for labor induction in the current pregnancy lower the success rate of vaginal delivery. An effective labor induction protocol leading to as high a rate of vaginal delivery as possible and a preparedness to respond to postpartum hemorrhage are paramount for avoiding negative childbirth experiences in women undergoing labor induction. In addition, enhancing nulliparous women’s confidence in their capacity and preparedness for labor and delivery could result in better experiences. Balloon catheter induction is safe in terms of infectious morbidity. It may also result in more positive views of the labor induction process, although the childbirth experiences associated with this practice seem to be similar to those of women who undergo labor induction via misoprostol. Practices for managing late-term pregnancy in the Finnish maternity care system should be assessed, as offering early induction at 41+0 gestational weeks may result in lower rates of operative delivery than the current protocol of implementing expectant management up to 41+5–42+1 gestational weeks. However, as perinatal outcomes were reassuring with both management options, expectant management may still be chosen if preferred by the pregnant woman.Suomessa joka kolmas synnytys käynnistetään. Käynnistetyssä synnytyksessä on suurempi riski keisarileikkaukselle ja huonolle synnytyskokemukselle, kun vertailukohtana on spontaanisti käynnistynyt synnytys. Joskus synnytyksen spontaania käynnistymistä ei kuitenkaan voida jäädä odottamaan, vaan äidin tai lapsen etu puoltaa käynnistystä. Tämä väitöskirja tutkii käynnistyksen vaikutuksia keisarileikkauksen ja muiden synnytyskomplikaatioiden esiintyvyyteen ja synnytyskokemukseen. Väitöskirja perustuu viiteen alkuperäisartikkeliin. Näistä kaksi on takautuvia kohorttitutkimuksia (I ja II), kaksi on kirjoitettu etenevästä kohorttitutkimuksesta (III–IV), ja yksi on satunnaistettu monikeskustutkimus (V, julkaisuarviossa). Tutkimuksen I tulosten perusteella aiemmin epäonnistuneen käynnistyksen tai pysähtyneen synnytyksen vuoksi keisarileikatuista synnyttäjistä suurin osa, 72,9%, synnytti alakautta jatkossa. Aiempi epäonnistunut käynnistys sekä käynnistys nykyisessä synnytyksessä oli kuitenkin merkittävä riskitekijä alatiesynnytysyrityksen epäonnistumiselle. Tutkimuksen II tulosten perusteella B-ryhmän streptokokkibakteerin kantajilla ei ollut riskiä synnyttäjän tai vastasyntyneen infektioiden lisääntymiseen, kun synnytys käynnistettiin balonkimenetelmällä sikiökalvojen ollessa lähtötilanteessa ehjät. Bakteerin kantajilla oli synnytyksen aikaisia infektioita jopa vähemmän kuin ei-kantajilla (4,7% vs. 8,3%, p = 0,01), mahdollisesti liittyen kantajille synnytyksen käynnistyttyä tai lapsiveden mentyä aloitettuun antibioottiprofylaksiaan. Tutkimuksen III–IV tulosten perusteella synnyttäjät kokivat käynnistyksellä alkaneet synnytyksensä melko positiivisena, ja suurin riski huonolle kokemukselle liittyi synnytyskomplikaatioihin: keisarileikkaukseen ja tavanomaista suurempaan verenvuotoon. Ensisynnyttäjien kokemusta omasta pärjäävyydestään tulisi kuitenkin vahvistaa. Balonki- ja misoprostolikäynnistysmenetelmiä verratessa synnytyskokemukset olivat yhtä hyvät, mutta balongilla käynnistetyt olivat tyytyväisempiä itse käynnistysmenetelmään. Tutkimuksen V tulosten perusteella pitkittyneen ensiraskauden käynnistysajankohdan varhentaminen raskausviikolta 41+5–42+1 raskausviikolle 41+0 saattaisi vähentää toimenpidesynnytysten osuutta, sillä varhaisemmin käynnistetyistä 30,6% synnytti imukuppi- tai keisarileikkausavusteisesti, kun seurantaryhmässä vastaavan toimenpidesynnytyksen koki 45,6%, p = 0,003. Kohtukuolemia ei tapahtunut eikä keisarileikkausten tai huonovointisten vastasyntyneiden osuuksissa ollut eroja. Liki puolella seurantaryhmäläisistä synnytys käynnistyi itsekseen. Varhaisemman käynnistyksen mahdollistamista kaikille sitä toivoville ensisynnyttäjille tulisi arvioida jatkossa Suomessa