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Obstetrics and gynaecology
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Routine induction in late-term pregnancies: follow-up of a Danish induction of labour paradigm
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  • Published on: 15 October 2021
    Response t o Pedersen´s second comment to our paper: "Routine induction in late-term pregnancies: follow-up of a Danish induction of labour paradigm""
    • Eva Rydahl, Associate Professor, Ph.d. Department of Midwifery University College Copenhagen

    We appreciate the interest that Dr. Pedersen has shown in our paper, but he has apparently misunderstood some aspects of our aim and analysis.

    Uterine ruptures: We do provide an explanation of why the change in ruptures from 2010 to 2012 is our main focus. The aim of this study was to evaluate implementation of a new protocol. The year 2011, serves as the year of implementation and the ITSA model fit an ordinary least square (OLS) line preintervention and postintervention. The reported results on uterine ruptures in the paper is in alignment with the study aim.

    Stillbirths: There have been several correspondences as well as meetings between Dr. Pedersen and representatives from our author group including a professor in biostatistics pointed out by the lead professor of Dr. Pedersens department. Our analysis has been reviewed by the external professor in biostatistics and found valid. We urge Dr. Pedersen to read among others the mail correspondence from May 10 and August 19 2020.

    Finally, we provide the rates of perinatal deaths pr. 1000 births before and after the protocol change in 2011 which may clarify for most people that a reduction of perinatal deaths due to the guideline change (the aim of our study) is unlikely, which supports the conclusion of our paper.

    Perinatal death rate (pr. 1000 births) 2009-2016, Denmark:
    2009: 0.9
    2010: 0.9
    2011: 0.6 Guideline change
    2012: <0.5
    2013: 1.3
    2014:...

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    Conflict of Interest:
    None declared.
  • Published on: 15 October 2021
    Response to Thisted and Krebs’: ”The relation of routine induction in late-term pregnancies to uterine rupture”
    • Eva Rydahl, Associate Professor, Ph.d. Department of Midwifery University College Copenhagen
    • Other Contributors:
      • Mette Juhl, Associate Professor, Ph.d. Department of Midwifery

    Thank you drawing attention to relevant aspects of uterine ruptures. Uterine rupture is a severe and rare outcome, and it is critical in the discussion about appropriate timing for induction of labour. Below, we address your comments on uterine ruptures one by one:

    Regarding overreporting of uterine rupture, in this study we were aware of misclassification of uterine ruptures. We discussed this and considered misclassification to be consistent over the study period. Therefore, a sudden change after 2011 is likely to indicate a true change in incidence.

    Regarding revision of ICD10 coding of uterine rupture, we were not aware of the discussion about coding practice in 2011, i.e. three years prior to your validation study in 2014. A change in coding practice would obviously have been relevant to consider in our interpretation of uterine rupture results. It is, however, difficult for us to further discuss the communication and revision, as your reference (#3) does not lead to information on changes in coding practice.

    Regarding previous CS, which is clearly highly relevant regarding uterine ruptures, our data showed that most of uterine rupture events (73 %) occurred in women with previous CS. This appeared from our paper and is in line with your comment.

    Regarding stratified results (e.g. by previous CS, as you suggest), the aim of this study was to examine implications of a change in a clinical practice that concerns all pregnant women at a cert...

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    Conflict of Interest:
    None declared.
  • Published on: 22 September 2021
    Response to Rydahl et al
    • Lars H Pedersen, Professor, Consultant Obstetrician Aarhus University / Aarhus University Hospital, Aarhus, Denmark

    I would like to acknowledge Dr. Rydahl and colleagues for the above reply that, however, does not address my concerns.

    Uterine ruptures:
    The authors still provide no explanation of why the change in ruptures from 2010 to 2012 (2.6‰ to 4.2‰) is specifically mentioned in the paper, including the abstract, while the larger change from 2006 to 2008 (1.0‰ to 2.9‰) receives no attention.

    Stillbirths:
    A linear spline model with equal intercept before and after a 2011 knot does not address my concerns regarding the stillbirth results published in the 2019 paper. The nature of the problem, however, depends on the specific model and the paper provides no details (in fact no such model was mentioned during our correspondence or meetings)
    Please provide the details of the suggested two linear spline models for stillbirths, i.e., the exact models with parameters. Further, please quantify the comparison between the models with and without an intercept change from 2011 and onwards..

    Conflict of Interest:
    Please see previous response
  • Published on: 22 September 2021
    The relation of routine induction in late-tern pregnancies to uterine rupture
    • Dorthe LA Thisted, Consultant Department of Obstetrics and Gynecology. Zealand University Hospital, Roskilde, Denmark
    • Other Contributors:
      • Lone Krebs, Professor

    We have, with great interest read the paper “Routine induction in late-term pregnancies: follow-up of a Danish induction of labour paradigm” (1) and the corresponding letters.
    We hereby allow us to add a few comments considering the authors conclusion regarding uterine rupture.
    Although monitoring of incidences of uterine rupture was not the main objective of the study, the authors conclude, that the most substantial impact of implementing routine induction of labour at GA 41+3, was an increased number of uterine ruptures.
    Rydahl et al (2019) (1) included data from the Danish Medical Birth Registry (DMBR) from the period of 2000-2016. In year 2014, we published a study validating the reporting of uterine ruptures to the DMBR in the period of 1997-2007 (2). We found a substantial overreporting of uterine rupture. Only 60,4% of the women with a reported uterine rupture, had a uterine rupture (partial or complete). We also realized that the coding of uterine rupture included a mixture of complete, incomplete and suspected uterine ruptures (2).
    A complete uterine rupture, defined as a direct communication between the uterine cavity and the peritoneum, is associated with both a very high perinatal mortality and morbidity and an immediate increased risk of severe hemorrhage or peripartum hysterectomy.
    A partiel uterine rupture is usually without any medical complications and is not associated to an increased maternal or perinatal morbidity. A partia...

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    Conflict of Interest:
    None declared.
  • Published on: 22 June 2021
    Response to Pedersen's comment to our paper "Routine induction in late-term pregnancies: follow-up of a Danish induction of labour paradigm
    • Eva Rydahl, Associate Professor, Ph.d. Department of Midwifery, University College Copenhagen

    We appreciate the interest that Dr. Pedersen has shown in our paper, but he has apparently misunderstood some aspects of our analysis. In the analysis of the stillbirth data, we first described the dependence of log (rate) on calendar year by a straight line. Next, we allowed the slope to change from 2011 onwards (a so-called linear spline with a knot at 2011). This did not improve the fit significantly. This is the analysis reported in our paper. Besides we also tried to see if a change in intercept from 2011 onwards would lead to a significantly better fit. This was not the case. This latter model is the one that Dr. Pedersen considers, but this was not the one presented in our paper.

    We are also concerned about Dr. Pedersen’s suggestion that we have been unresponsive to his questions. We can document at least 11 email correspondences and two face to face meetings with Dr. Pedersen to accommodate Dr. Pedersen’s wish for more information and discussion of our analyses. These mails and meetings have also included the Lead Professor of Dr. Pedersen’s department and a Professor in Biostatistics from Aarhus University. The Professor in Biostatistics has confirmed to all included in the meetings and in the additional emails that our analysis as well as our conclusions in the paper were valid.

    Eva Rydahl, Eugene Declercq, Mette Juhl, Rikke Damkjær Maimburg

    Conflict of Interest:
    None declared.
  • Published on: 2 June 2021
    Issues with the statistical models, Rydahl et al, BMJ Open, 2019
    • Lars H Pedersen, Professor, Consultant Obstetrician Aarhus University, Depts. Clinical Medicine & Biomedicine. Aarhus University Hospital, Obstetrics & Gynecology, Aarhus, Denmark

    I would like to point to potential problems with the statistical models of Rydahl et al:

    For stillbirths, they fit a Poisson model log(rate) = a + b*year + c*dummy(2011) (dummy(2011) is 0 before and 1 after the change in guideline) [personal communication], a model that obviously allow for no change in the slope before and after 2011. This is problematic because the actual data indicate that the stillbirth rate decreases up to 2011 and increases after 2011 (acknowledged by Rydahl et al (p. 6) and suggested by a recent paper based on similar data [1]). Because the model is underfitted, the findings may be unreliable (false negative).
    A basic simulation illustrates the problem: the underlying hypothesis is that the stillbirth rate reflects the induction rate (i.e. the number of ongoing pregnancies) and that stillbirths consequently reflects the Figure 2A changes over time. If the risk of stillbirth is proportional to the number of ongoing pregnancies, one simple simulated data could be per year n=16, 16, 14, 13, 12, 12, 11, 11, 11, 10, 11, 8, 5, 6, 6, 7, 8 from 2000 to 2016. The model applied by Rydahl et al would be unable to detect the build-in change in this simulated data. In fact, as expected, only some models would be able to detect the change: for example, in a quasi-Poisson model with interaction, the before-after dummy is statistically significant (p=0.045). Interestingly, if this model is applied to the published data, the dummy(2011) is statistically...

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    Conflict of Interest:

    The last author and I are employed at the same department, and I participate in a working group under the National Board of Health with the first author. They have been informed several times about my concerns by e-mails and at meetings. Because the discussions have led to no common ground, I feel compelled to comment in public.
  • Published on: 3 January 2020
    Response to Lidegaard et al.'s comment to our paper "Routine induction in late-term pregnancies: follow-up of a Danish induction of labour paradigm
    • Rikke D Maimburg, Associate Professor Department of Clinical Medicine, Aarhus University Hospital

    We appreciate the interest in our recently published paper on induction of labour and the very quick response by Lidegaard et al., giving us the opportunity to elaborate on the assumptions and questions raised.

    Our comments are listed below:
    Lidegaard et al. state that our study in BMJ Open is “yet an attempt to question a more offensive post-term induction practice” perhaps with a reference to a peer reviewed systematic review published earlier this year. First, we would like to point towards a professional way of communicating. Everyone, both the women and the professionals will benefit if we agree on being professional in our way of discussing research and clinical practice. Having said so, it is correct, that two of the authors of our BMJ Open publication have published a systematic review comparing routine induction of labour at 41+0/6 gestational weeks to 42+0/6 gestational weeks [1]. The systematic review revealed adverse maternal outcomes associated with routine induction of labour at 41+0/6 gestational weeks as well as both benefits and harms for the newborns by each regime. In the current paper, we did not study any offensive post-term labour induction practice as suggested by Lidegaard et al., but the practice of treating otherwise healthy pregnant women at 41+3/5 gestational weeks, where they are within the normal range of pregnancy and not yet post-term.
    We do not agree on the simple causal argumentation suggested by Lidegaard et al. based...

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    Conflict of Interest:
    None declared.
  • Published on: 19 December 2019
    Record low stillbirth rates in Denmark
    • Øjvind Lidegaard, Professor in Obstetrics & GynaecologyMD, DMSci Rigshospitalet, University of Copenhagen
    • Other Contributors:
      • Niels Uldbjerg, Professor in Obstetrics
      • Morten Hedegaard, MD, specialist in Obstetrics and Gynaecology

    Thanks to Rydahl et al. for yet an attempt to question a more offensive post-term induction practice to have a main responsibility for the impressing reduction in stillbirths in Denmark (1). The more offensive induction practice was gradually implemented in Denmark through this century but accelerated by the National recommendation in 2010-2011 to induce post-term women so to ensure delivery before 42 gestational weeks (GW).
    The following comments assume that the data presented by Rydahl et al. are correct, we are currently looking at the same issue and the same data.
    First what we agree on:
    • There has from 2000 to 2012 been a substantial decrease in stillbirths in Denmark among women pregnant beyond 41+3 GW. The reduction was from 2.6 to <0.5 stillbirths per 1000 delivered, a reduction of at least 80%. Shouldn’t we start by congratulating each other for this impressing National achievement.
    • During the same period has the proportion of induced deliveries increased for women going beyond 41+3 GW from 25% to around 65%.
    • Despite this dramatic change in induction practice, both Caesarean section rates, low Apgar scores, and birth augmentation have been almost stable.
    • The proportion of instrumental births has decreased during the same period.

    It is of course an important issue what caused the dramatic decrease in stillbirths over the last two decades in Denmark. We have previously published evidence arguing that the more offe...

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    Conflict of Interest:
    None declared.