Key results

The aim of this study was to review the current literature regarding the Finnish intervention. Our systematic literature search identified seven studies evaluating the effect of the intervention, none of which were randomised or blinded. The evidence level was 2c or lower. They found that the implementation of the Finnish intervention was followed by significant reductions in OASIS and significant increases in the use of episiotomy.

Summary of evidence level

The evidence supporting the Finnish intervention is limited, as it is based on only seven studies with receding quality. The authors furthermore belong to a restricted group working on the basis of exclusively Nordic data, some of which were used in three studies.14 ,28 ,29 No causal effects can be established as none of the studies were randomised, blinded or compared the intervention to a concurrent controlled group. Furthermore, the intervention was not carried out in a standardised or controlled way. Despite these obvious limitations, the studies conclude that the occurrence of OASIS is reduced as a result of the Finnish intervention. 5–8 ,14 ,28 ,29 This is particularly worrying in the case of the frequently cited study by Pirhonen et al5 which aimed to compare frequencies of OASIS. This study was not predefined or designed to evaluate effects of the Finnish manoeuvre, but the authors suggested on the basis of educational books and personal experiences that the significantly lower frequency of OASIS in Finland compared to Sweden could be explained by the use of the manoeuvre in Finland.

Interpretation of the current evidence level

Methodological limitations related to the available studies of the Finnish intervention mean that the reported reduction of OASIS may potentially be accounted for by several other factors such as confounders or competing risk. A key point for consideration is that the Finnish intervention (see the background section and box 1) consists of four elements. One element with a negative influence on the outcome may thus have counteracted a positive effect of another element, and vice versa. Although none of the studies attempted to determine the effect of the individual elements, several of the studies claim that the manual support technique (the Finnish manoeuvre, box 1) is the most important part of the intervention and the one that constitutes the basis of the observed significant reduction in OASIS.8 ,14 ,28 ,29 Critics, however, argue that other manual support techniques could replace the Finnish manoeuvre provided that the other three elements of the Finnish intervention were retained.19 We maintain that the effect of the Finnish intervention remains unclear and that the theoretical basis for its main element, the Finnish manoeuvre, is questionable. We are concerned about the implications of a procedure that forces the infant's emerging neck to flex at crowning, whereby the presenting diameter is likely to increase. As the fetal head circumference is a well-known OASIS risk indicator, we urge further study of the Finnish manoeuvre's physiology before its use can be recommended.2 In assessing the Finnish intervention, it should also be considered that its introduction was accompanied by intense training and educational programmes.8 ,10 ,14 The Hawthorne effect is known to predict an independent effect of increasing the attention to a problem.30 Furthermore, since the Finnish intervention was not executed in a controlled way, the staff in hospitals and/or regions who had reduction of OASIS as a focus point may have combined the intervention with other common preventive techniques, such as warm compression or massage of the perineum, that have a documented effect on reduction of OASIS.2 Finally, episiotomy techniques have changed during the study periods. Hals et al14 reported that median episiotomy had been used before, while lateral or mediolateral episiotomy was used after the Finnish intervention was introduced. As median episiotomy is known to be a significant risk factor for OASIS,31 this shift may have contributed to the declining incidence.

Unexplored adverse effects and suggestions for research

Though the well-being of the infant should be considered before any intervention, little attention has been given to this aspect with only three studies reporting on fetal outcome. 5 ,14 ,29 Although the effect of the Finnish intervention on the length of the second stage has not been sufficiently evaluated,5 the intervention is likely to slow down the crowning of the fetus, at the same time slightly increasing the period of maximum pressure to the fetal head. The conflicting findings on the Apgar score 5 ,14 ,29 indicate a need for further studies of perinatal effects. Use of umbilical blood gases as a measurement would be a more objective indicator for infant well-being, but missing data could be a challenge as a test of umbilical blood gases is not routinely used in all birth settings.

The studies report an increase in the use of episiotomy after the implementation of the Finnish intervention. Although the evidence is contested, episiotomy is used to expedite birth, indicated, for example, by fetal distress, and to avert severe perineal trauma. Several studies have shown that an episiotomy is equally painful and involves tearing of the same structures as a second-degree spontaneous perineal laceration,32 ,33 and the literature generally recommends a restricted use of episiotomy.22 Episiotomy in the Finnish intervention should only be performed on indication.8 ,14 ,28 ,29 Although the use of episiotomy is thus restricted, indications include rigid perineum and imminent perineal tear. In a Nordic setting where episiotomy rates have for decades been low and routine use of episiotomy has been abandoned, this is a widening of the indications for episiotomy which may explain the increased use of episotomy following the implementation of the Finnish intervention. Laine et al7 suggest that as the episiotomy rate has increased, the incidence of OASIS has dropped, but limited evidence for this causal relationship is presented. Räisänen et al34 have estimated that 909 lateral episiotomies are needed to avert one anal sphincter injury. Although the perineal damage caused by episiotomy is less severe than the damage related to OASIS and therefore preferable, interventions that increase the use of episiotomy should be closely monitored.

The pain and discomfort of perineal trauma perceived by women essentialise efforts to minimise not only OASIS but also all traumas to the genital tract. We suggest that future research should investigate the effect of the Finnish intervention on first and second-degree perineal laceration as well as intact perineum; a favourable birth outcome with a positive influence in, for example, women's sexual life postpartum.35 ,36 Finally, future research should give more attention to the effects of the Finnish intervention on women's birth positions and perceptions of the intervention. Encouragement of women to use a delivery position that allows execution of the Finnish intervention and visual examination of the perineum during the last minutes of delivery could be problematic, as it may affect birth experiences and violate women's right to an informed choice in child birth. Moreover, it runs counter to recommendations in a Cochrane review.21

Finally, further research should take into account that factors such as episiotomy, duration of second stage of labour and birth position have the potential to be confounders or competing risk factors when evaluating the effect of the Finnish intervention to decrease the incidence of OASIS. The study designs and methods used in the current studies do not allow for determination of whether the factors had a positive, negative or neutral influence on the incidence of OASIS. In five of the included studies, an attempt to identify and remove potential risk factors for OASIS with multivariate analysis has been conducted,5 ,8 ,14 ,28 ,29 but as stated, only two studies describe which factors have been taken into account,8 ,29 and it is unclear if the decrease in OASIS is still significant in the multivariate analysis.

Strengths and limitations

The strength of this study lies in its foundation in the systematic, comprehensive and reproducible literature search based on the PICO approach24 and searches in the international English language as well as Scandinavian language article databases. A search of Finnish language studies would have further strengthened our strategy but to counter a potential oversight of relevant articles, the reference lists of the included studies were also searched. A rigorous appraisal of the included studies was performed and the transparency and reproducibility of this review is supported by its adherence to STROBE requirements25 and the PRISMA statement.23

What this study adds

This study adds to the understanding of a four-element approach to OASIS prevention that is rapidly being introduced in many obstetric units, especially in the Nordic countries and the UK. We suggest that the term, ‘the Finnish intervention’, should be used to ensure the clarity of concepts and increased generalisability of findings, as we find evidence in the literature that the intervention is confused with the general use of techniques for manual support of the perineum. Furthermore, our study is the first to offer an overview of the evidence underlying the Finnish intervention, based on a comprehensive and systematic approach in accordance with criteria for evidence-based medicine. Our study demonstrates that the theoretical foundation and causal relationship proposed in support of the Finnish intervention are as yet insufficient. We find that the evidence level underlying the intervention does not meet the requirements of evidence-based medicine and wish to voice our concern regarding the lack of investigation of potential adverse effects. Despite this, there is no indication in the literature that women are given an informed choice of the Finnish intervention and no exploration of women's experiences with the intervention seems to have been attempted as yet.

Implication for practice

The risk of severe potential short-term and long-term effects of OASIS for new mothers makes their prevention a priority in practice and research. Still, our findings in this systematic review do not support a broad-scale introduction of the Finnish intervention in clinical settings at this point. Uncertainty about the potential adverse effects and causation highlights the need for investigation of a broader range of maternal and perinatal effects in studies providing higher levels of evidence, such as randomised controlled trials (RCTs). RCTs may be difficult to carry out due to the four elements of the intervention that must all be taken into consideration and performed according to protocol. A question that arises is whether the Finnish interventions should be considered as a whole or if the elements should be investigated separately. We believe that since the Finnish manoeuvre is described as the most important element, this should be the focus of the trials. An RCT could be formed by comparing the Finnish intervention with another intervention such as applying the warm compressions instead of the Finnish manoeuvre and maintaining the other three elements. Conducting an RCT is likely to be challenging but not impossible as other manual perineal protection methods have already been tested using RCTs.2

In the absence of solid evidence, we encourage clinicians to monitor the occurrence of OASIS, to implement interventions with documented positive effects, including the use of warm perineal compressions and massage during the second stage of labour,2 and to stimulate discussions of best practice. Where the Finnish intervention has already been implemented, we urge management and staff to perform quality assessments and ensure that balanced information is offered to women.