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Featured researches published by Marjolein Kok.


Obstetrics & Gynecology | 2008

External Cephalic Version-Related Risks A Meta-analysis

K. Grootscholten; Marjolein Kok; S.G. Oei; Ben Willem J. Mol; J.A. van der Post

OBJECTIVE: To systematically review the literature on external cephalic version–related complications and to assess if the outcome of a version attempt is related to complications. DATA SOURCES: In March 2007 we searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials. METHODS OF STUDY SELECTION: Studies reporting on complications from an external cephalic version attempt for singleton breech pregnancies after 36 weeks of pregnancy were selected. We calculated odds ratios (ORs) from studies that reported both on complications as well as on the position of the fetus immediately after the procedure. TABULATION, INTEGRATION, AND RESULTS: We found 84 studies, reporting on 12,955 version attempts that reported on external cephalic version–related complications. The pooled complication rate was 6.1% (95% CI 4.7–7.8), 0.24% for serious complications (95% confidence interval [CI] 0.17–0.34) and 0.35% for emergency cesarean deliveries (95% CI 0.26–0.47). Complications were not related to external cephalic version outcome (OR 1.2 (95% CI 0.93–1.7). CONCLUSION: External cephalic version is a safe procedure. Complications are not related to the fetal position after external cephalic version.


American Journal of Obstetrics and Gynecology | 2008

Clinical factors to predict the outcome of external cephalic version : a metaanalysis

Marjolein Kok; Jeltsje S. Cnossen; Lonneke Gravendeel; Joris A. M. van der Post; Brent C. Opmeer; Ben Willem J. Mol

OBJECTIVE The objective of the study was to systematically review the medical literature reporting on potential clinical prognosticators for the outcome of external cephalic version (ECV). STUDY DESIGN Medline, EMBASE, and Cochrane Central Register of Controlled Trials were searched. Studies reporting on potential clinical prognosticators and ECV success rates that allowed construction of a 2 x 2 table were selected. RESULTS We detected 53 primary articles reporting on 10,149 women. Multiparity (P >/= 1.00; odds ratio [OR], 2.5; 95% confidence interval [CI], 2.3-2.8), nonengagement of the breech (OR, 9.4; 95% CI, 6.3-14), a relaxed uterus (OR, 18; 95% CI, 12-29), a palpable fetal head (OR, 6.3; 95% CI, 4.3-9.2), and maternal weight less than 65 kg (OR, 1.8; 95% CI, 1.2-2.6) were predictors for successful external cephalic version. CONCLUSION Success of an ECV attempt is associated with clinical factors. This should be taken into account in the counseling of women prior to an ECV attempt.


British Journal of Obstetrics and Gynaecology | 2013

Decision aids to improve informed decision-making in pregnancy care: a systematic review

Floortje Vlemmix; Janna K. Warendorf; Ageeth N. Rosman; Marjolein Kok; Ben Willem J. Mol; Jonathan M. Morris; Natasha Nassar

Rapid development in health care has resulted in an increasing number of screening and treatment options. Consequently, there is an urgency to provide people with relevant information about benefits and risks of healthcare options in an unbiased way. Decision aids help people to make decisions by providing unbiased non‐directive research evidence about all treatment options.


Acta Obstetricia et Gynecologica Scandinavica | 2014

Term breech deliveries in the Netherlands: did the increased cesarean rate affect neonatal outcome? A population‐based cohort study

Floortje Vlemmix; Lester Bergenhenegouwen; Jelle Schaaf; Sabine Ensing; Ageeth N. Rosman; Anita Ravelli; Joris A. M. van der Post; Arno Verhoeven; Gerard H.A. Visser; Ben W. J. Mol; Marjolein Kok

The aim of this study was to evaluate the effect of the increased cesarean rate for term breech presentation on neonatal outcome. We also investigated whether the clinical case selection for vaginal delivery applied by Dutch obstetricians led to an optimization of neonatal outcome, or whether there is still room for improvement in terms of perinatal outcome.


European Journal of Obstetrics & Gynecology and Reproductive Biology | 2014

Vaginal delivery versus caesarean section in preterm breech delivery: a systematic review

L.A. Bergenhenegouwen; Linda Meertens; Jelle Schaaf; Jan G. Nijhuis; B.W. Mol; Marjolein Kok; Hubertina C. J. Scheepers

There is controversy on the preferred mode of delivery (vaginal delivery (VD) versus caesarean section (CS)) in preterm breech delivery in relation to neonatal outcome. While CS is supposed to be safer for the fetus, arguments against CS can be the increased risk of maternal morbidity, risks for future pregnancies, and costs. Moreover, neonatal respiratory distress syndrome occurs more frequently after CS compared to VD. In the past, several RCTs have been started on this subject, but they were all preliminary and stopped due to recruitment difficulties. As the Cochrane review of these RCTs reported on 116 women only, knowledge on the effectiveness of CS and VD can at present only be obtained from non-randomized studies. We performed a systematic review and meta-analysis of non-randomized studies that assessed the association between mode of delivery and neonatal mortality in women with preterm breech presentation. We searched Pubmed, Embase and the Cochrane library for articles comparing neonatal mortality after VD versus CS in preterm breech presentation (gestational age 25(+0) till 36(+6) weeks). Seven studies, involving a total of 3557 women, met the eligibility criteria and were included in this systematic review. The weighted risk of neonatal mortality was 3.8% in the CS group and 11.5% in the VD group (pooled RR 0.63 (95% CI 0.48-0.81)). We conclude that cohort studies indicate that CS reduces neonatal mortality as compared to VD.


American Journal of Perinatology | 2011

Prediction of success of external cephalic version after 36 weeks.

Marjolein Kok; Jan Willem van der Steeg; Joris A. M. van der Post; Ben Willem J. Mol

We aimed to develop a predictive model for the chance of a successful external cephalic version (ECV). We performed a prospective cohort study of women with a singleton fetus in breech presentation with a gestational age of 36 weeks or more. Data on parity, maternal age, body mass index, ethnicity, gestational age, placental location, fetal position, estimated fetal weight, and amniotic fluid were recorded in all participants. Multivariable logistic regression analysis with a stepwise backward selection procedure was used to construct a prediction model for the occurrence of successful ECV. We included a total of 310 women. Multivariable logistic regression analysis demonstrated that multiparity, increasing estimated fetal weight, and normal amniotic fluid were favorable predictors of successful ECV. Anterior placenta location was an unfavorable predictor for ECV outcome. Discrimination of the model was fair (area under the curve 0.71), and the calibration of the model was acceptable. Our prediction model appears to discriminate between women with a poor chance of successful ECV (less than 20%) and women with a good chance of success (more than 60%). When this model is validated externally, it could be used for patient counseling and clinical decision making.


Obstetrics & Gynecology | 2014

Mode of delivery after successful external cephalic version: a systematic review and meta-analysis.

Marcella de Hundt; Joost Velzel; Christianne J.M. de Groot; Ben Willem J. Mol; Marjolein Kok

OBJECTIVE: To assess the mode of delivery in women after a successful external cephalic version by performing a systematic review and meta-analysis. DATA SOURCES: We searched MEDLINE, Embase, ClinicalTrials.gov, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library for studies reporting on the mode of delivery in women after successful external cephalic version at term and women with a spontaneous cephalic-presenting fetus. METHODS OF STUDY SELECTION: Two reviewers independently selected studies, extracted data, and assessed study quality. The association between mode of delivery and successful external cephalic version was expressed as a common odds ratio with a 95% confidence interval (CI). TABULATION, INTEGRATION, AND RESULTS: We identified three cohort studies and eight case–control studies, reporting on 46,641 women. The average cesarean delivery rate for women with a successful external cephalic version was 21%. Women after successful external cephalic version were at increased risk for cesarean delivery for dystocia (odds ratio [OR] 2.2, 95% CI 1.6–3.0), cesarean delivery for fetal distress (OR 2.2, 95% CI 1.6–2.9), and instrumental vaginal delivery (OR 1.4, 95% CI 1.1–1.7). CONCLUSION: Women who have had a successful external cephalic version for breech presentation are at increased risk for cesarean delivery and instrumental vaginal delivery as compared with women with a spontaneous cephalic presentation. Nevertheless, with a number needed to treat of three, external cephalic version still remains a very efficient procedure to prevent a cesarean delivery. LEVEL OF EVIDENCE: (Data for is not given in the PDF but is given in PDFs of other chapters, please confirm with PE)


Acta Obstetricia et Gynecologica Scandinavica | 2013

Contraindications for external cephalic version in breech position at term: a systematic review

Ageeth N. Rosman; Aline Guijt; Floortje Vlemmix; Marlies Rijnders; Ben Willem J. Mol; Marjolein Kok

Objective. External cephalic version (ECV) is a safe and effective intervention that can prevent breech delivery, thus reducing the need for cesarean delivery. It is recommended in national guidelines. These guidelines also mention contraindications for ECV, and thereby restrict the application of ECV. We assessed whether the formulation of these contraindications in guidelines are based on empiric data. Design. Systematic review. Population. Pregnant women with a singleton breech presentation from 34 weeks. Methods. We searched the National Guideline Clearinghouse, the Cochrane Central Register of Controlled Trials, MEDLINE (1953–2009), EMBASE (1980–2009), TRIP database (until 2011), NHS (National Health Services, until 2011), Diseases database (until 2011) and NICE guidelines (until 2011) for existing guidelines on ECV and studied the reproducibility of the contraindications stated in the guidelines. Furthermore, we systematically reviewed the literature for contraindications and evidence on these contraindications. Main outcome measures. Contraindications of ECV. Results. We found five guidelines mentioning 18 contraindications, varying from five to 13 per guideline. The contraindications were not reproducible between the guidelines with oligohydramnios as the only contraindication mentioned in all guidelines. The literature search yielded 60 studies reporting on 39 different contraindications, of which we could only assess evidence of six of them. Conclusion. The present study shows that there is no general consensus on the eligibility of patients for ECV. Therefore we propose to limit contraindications for ECV to clear empirical evidence or to those with a clear pathophysiological relevance.


The Lancet | 2016

Nifedipine versus atosiban for threatened preterm birth (APOSTEL III): a multicentre, randomised controlled trial

Elvira O.G. van Vliet; Tobias A.J. Nijman; Ewoud Schuit; Karst Y. Heida; Brent C. Opmeer; Marjolein Kok; Wilfried Gyselaers; Martina Porath; Mallory Woiski; Caroline J. Bax; Kitty W. M. Bloemenkamp; Hubertina C. J. Scheepers; Yves Jacquemyn; Erik van Beek; Johannes J. Duvekot; Maureen Franssen; Dimitri Papatsonis; Joke H. Kok; Joris A. M. van der Post; Arie Franx; Ben Willem J. Mol; Martijn A. Oudijk

BACKGROUND In women with threatened preterm birth, delay of delivery by 48 h allows antenatal corticosteroids to improve neonatal outcomes. For this reason, tocolytics are often administered for 48 h; however, there is no consensus about which drug results in the best maternal and neonatal outcomes. In the APOSTEL III trial we aimed to compare the effectiveness and safety of the calcium-channel blocker nifedipine and the oxytocin inhibitor atosiban in women with threatened preterm birth. METHODS We did this multicentre, randomised controlled trial in ten tertiary and nine teaching hospitals in the Netherlands and Belgium. Women with threatened preterm birth (gestational age 25-34 weeks) were randomly assigned (1:1) to either oral nifedipine or intravenous atosiban for 48 h. An independent data manager used a web-based computerised programme to randomly assign women in permuted block sizes of four, with groups stratified by centre. Clinicians, outcome assessors, and women were not masked to treatment group. The primary outcome was a composite of adverse perinatal outcomes, which included perinatal mortality, bronchopulmonary dysplasia, sepsis, intraventricular haemorrhage, periventricular leukomalacia, and necrotising enterocolitis. Analysis was done in all women and babies with follow-up data. The study is registered at the Dutch Clinical Trial Registry, number NTR2947. FINDINGS Between July 6, 2011, and July 7, 2014, we randomly assigned 254 women to nifedipine and 256 to atosiban. Primary outcome data were available for 248 women and 297 babies in the nifedipine group and 255 women and 294 babies in the atosiban group. The primary outcome occurred in 42 babies (14%) in the nifedipine group and in 45 (15%) in the atosiban group (relative risk [RR] 0·91, 95% CI 0·61-1·37). 16 (5%) babies died in the nifedipine group and seven (2%) died in the atosiban group (RR 2·20, 95% CI 0·91-5·33); all deaths were deemed unlikely to be related to the study drug. Maternal adverse events did not differ between groups. INTERPRETATION In women with threatened preterm birth, 48 h of tocolysis with nifedipine or atosiban results in similar perinatal outcomes. Future clinical research should focus on large placebo-controlled trials, powered for perinatal outcomes. FUNDING ZonMw (the Netherlands Organisation for Health Research and Development).


Midwifery | 2014

Patients' and professionals' barriers and facilitators to external cephalic version for breech presentation at term, a qualitative analysis in the Netherlands

Ageeth N. Rosman; Floortje Vlemmix; M.A.H. Fleuren; Marlies Rijnders; Antje Beuckens; Brent C. Opmeer; Ben W. J. Mol; M.C.B. van Zwieten; Marjolein Kok

OBJECTIVE external cephalic version (ECV) is a relatively simple and safe manoeuvre and a proven effective approach in the reduction of breech presentation at term. There is professional consensus that ECV should be offered to all women with a fetus in breech presentation, but only up to 70% of women eligible for ECV undergo an ECV attempt. The aim of the study was to identify barriers and facilitators for ECV among professionals and women with a breech presentation at term. DESIGN qualitative study with semi-structured interviews. SETTING Dutch hospitals. PARTICIPANTS pregnant women with a breech presentation who had decided on ECV, and midwives and gynaecologists treating women with a breech presentation. MEASUREMENTS on the basis of national guidelines and expert opinions, we developed topic lists to guide the interviews and discuss barriers and facilitators in order to decide on ECV (pregnant women) or advice on ECV (midwives and gynaecologists). FINDINGS among pregnant women the main barriers were fear, the preference to have a planned caesarean section (CS), incomplete information and having witnessed birth complications within the family or among friends. The main facilitators were the wish for a home birth, the wish for a vaginal delivery and confidence of the safety of ECV. Among professionals the main barriers were a lack of knowledge to fully inform and counsel patients on ECV, and the inability to counsel women who preferred a primary CS. The main facilitator was an unambiguous policy on (counselling for) ECV within the region. CONCLUSION we identified several barriers and facilitators possibly explaining the suboptimal implementation of ECV for breech presentation in the Netherlands. This knowledge should be taken into account in designing implementation strategies for ECV to improve the uptake of ECV by professionals and patients.

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Hubertina C. J. Scheepers

Maastricht University Medical Centre

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Maureen Franssen

University Medical Center Groningen

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Mallory Woiski

Radboud University Nijmegen

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