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Dive into the research topics where Hans M.W.M. Merkus is active.

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Featured researches published by Hans M.W.M. Merkus.


Fertility and Sterility | 2002

Effects of folic acid and zinc sulfate on male factor subfertility: a double-blind, randomized, placebo-controlled trial

Wai Yee Wong; Hans M.W.M. Merkus; Christopher M. Thomas; Roelof Menkveld; Gerhard A. Zielhuis; Régine P.M. Steegers-Theunissen

OBJECTIVE To study the effects of folic acid and zinc sulfate treatment on semen variables in fertile and subfertile men. DESIGN Double-blind, placebo-controlled interventional study. SETTING Two outpatient fertility clinics and nine midwifery practices in The Netherlands. PARTICIPANT(S) One hundred eight fertile and 103 subfertile men. INTERVENTION(S) Both groups were randomly assigned to receive one of four treatments for 26 weeks: folic acid and placebo, zinc sulfate and placebo, zinc sulfate and folic acid, and two placebos. Folic acid was given at a daily dose of 5 mg, and zinc sulfate was given at a daily dose of 66 mg. MAIN OUTCOME MEASURE(S) Before and after treatment, standardized semen and blood samples were obtained for determinations of sperm concentration, motility, and morphology according to World Health Organization guidelines; semen morphology according to strict criteria; and blood folate and zinc concentrations. Effects of the four interventions were evaluated separately in subfertile and fertile men. RESULT(S) Subfertile men demonstrated a significant 74% increase in total normal sperm count and a minor increase of 4% abnormal spermatozoa. A similar trend was observed in fertile men. Pre-intervention concentrations of folate and zinc in blood and seminal plasma did not significantly differ between fertile and subfertile men. CONCLUSION(S) Total normal sperm count increases after combined zinc sulfate and folic acid treatment in both subfertile and fertile men. Although the beneficial effect on fertility remains to be established, this finding opens avenues of future fertility research and treatment and may affect public health.


Reproductive Toxicology | 2001

The impact of calcium, magnesium, zinc and copper in blood and seminal plasma on semen parameters in men

Wai Yee Wong; Gert Flik; Pascal M.W. Groenen; Dorine W. Swinkels; Christopher M. Thomas; Jenny H.J. Copius-Peereboom; Hans M.W.M. Merkus; Régine P.M. Steegers-Theunissen

To investigate the impact of calcium, magnesium, zinc, and copper in blood and seminal plasma on semen parameters, 107 fertile and 103 subfertile males provided a standardized blood and semen specimen. Total calcium and magnesium concentrations were determined with colorimetric end point assay procedures. Zinc and copper were determined by flame atomic absorption spectrophotometer (AAS). Semen analysis was performed according to World Health Organization guidelines (1992). The concentrations of calcium, magnesium, zinc, and copper in blood and seminal plasma were not different between the subfertile and fertile group. Weak correlations were demonstrated between blood plasma zinc concentrations and sperm count (rs = 0.18), sperm motility (rs = 0.15), and abnormal sperm morphology (rs = 0.13). Zinc and magnesium concentrations in seminal plasma correlated weakly with sperm count (rs = 0.17 and rs = 0.16, respectively), and copper concentrations in blood plasma with motility (rs = 0.25). Strong correlations were found between calcium, magnesium, and zinc in seminal plasma. Although calcium, magnesium, zinc, and copper play an essential role in spermatogenesis and fertility, the determination of these elements in blood and seminal plasma does not discriminate on the basis of fertility in this group of men.


Epidemiology | 2001

Smoking, Genetic Polymorphisms in Biotransformation Enzymes, and Nonsyndromic Oral Clefting: A Gene-environment Interaction

Iris van Rooij; Manon J. M. Wegerif; Henny M. J. Roelofs; Wilbert H.M. Peters; Anne-Marie Kuijpers-Jagtman; Gerhard A. Zielhuis; Hans M.W.M. Merkus; Régine P.M. Steegers-Theunissen

The importance of maternal smoking in the pathogenesis of oral facial clefts is not clear. Susceptibility to cigarette smoke depends on biotransformation of the toxic compounds by mother and embryo. In a population-based case-control study, we investigated the effects of maternal smoking during the first pregnancy trimester and the interaction with polymorphisms in the biotransformation enzymes cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase theta 1–1 (GSTT1) on the risk of nonsyndromic oral clefting in the offspring. We recruited 113 infants with nonsyndromic oral clefts and their mothers, as well as 104 control infants and their mothers. Maternal smoking habits were collected regarding the period 3 months before through 3 months after conception. Buccal swabs were taken from mothers and infants for genetic analysis. Maternal smoking was not strongly associated with oral clefting (odds ratio = 1.1; 95% confidence interval = 0.6–2.2), nor were CYP1A1 and GSTT1 polymorphisms. Mothers who smoked and carried the GSTT1-null genotype, however, had an increased risk for having a child with oral clefting compared with nonsmokers with the wild type genotype (odds ratio = 3.2; 95% confidence interval = 0.9–11.6). The risk was almost five times greater (odds ratio = 4.9; 95% confidence interval = 0.7–36.9) in mothers and infants both having the GSTT1-null genotype compared with both having the wild genotype. There was no interaction between CYP1A1 and maternal smoking in relation to oral clefting.


Fertility and Sterility | 2000

Cigarette smoking and the risk of male factor subfertility: minor association between cotinine in seminal plasma and semen morphology

Wai Yee Wong; Christopher M. Thomas; Hans M.W.M. Merkus; Gerhard A. Zielhuis; Wim H. Doesburg; Régine P.M. Steegers-Theunissen

OBJECTIVE To evaluate the impact of cigarette smoking on male factor subfertility and the semen parameters of sperm count, motility, and morphology by questionnaire and determination of the cotinine concentrations in blood and seminal plasma of fertile and subfertile males. DESIGN Case-control study of 107 fertile and 103 subfertile males who provided a standardized blood and semen specimen and completed a self-administered questionnaire about their smoking habits. SETTING Outpatient fertility clinic of the University Medical Centre St. Radboud, Nijmegen, The Netherlands. PATIENT(S) One hundred seven fertile and 103 subfertile males. INTERVENTION(S) Vena puncture and semen collection. MAIN OUTCOME MEASURE(S) Blood and seminal plasma cotinine levels in relation to semen parameters. RESULT(S) A higher frequency of cigarette smoking was observed in subfertile males than in fertile males, with an odds ratio of 1.7 (95% confidence interval, 0.9-3.2). The self-reported number of cigarettes smoked per day correlated with the cotinine concentrations in blood and seminal plasma for both groups. A small but statistically significant correlation was found between cotinine concentrations in seminal plasma and the percentage of abnormal sperm morphology, but not for other semen parameters (r(s) = 0.19). CONCLUSION(S) Although the mechanism of the toxicity of cotinine on sperm morphology is not clear, this study indicates only a minor effect of cigarette smoking on male factor subfertility, which is probably due to compounds in cigarette smoke other than nicotine (cotinine).


Epilepsy Research | 1994

Factors influencing the risk of abnormal pregnancy outcome in epileptic women: a multi-centre prospective study.

Régine P.M. Steegers-Theunissen; W.O. Renier; George F. Borm; Chris M.G. Thomas; Hans M.W.M. Merkus; Dolf A.W.Op de Coul; Pieter A. De Jong; Herman P. van Geijn; M.G.A.J. Wouters; T.K.A.B. Eskes

We studied pregnancy outcome in preconceptionally recruited epileptic and control women in a multi-centre prospective non-intervention study at two university hospitals and three general hospitals. We evaluated 225 singleton pregnancies: 119 pregnancies of epileptic women who received either antiepileptic drugs (AEDs) (n = 99) or not (n = 20), and 106 pregnancies of controls. The main outcome measures were abnormal pregnancy outcome: major and minor congenital malformations, ectopic pregnancies, abortions; neonatal headcircumference; birth weight and birth length. Epileptic women had a two-fold risk of having an abnormal pregnancy outcome or an infant with minor malformations compared to healthy controls (odds ratio, with 95% confidence interval, respectively 2.1 (1.1, 4.0) and 2.0 (1.0, 4.0)). A significant correlation between the prevalence of abnormal pregnancy outcome and duration of epilepsy and AED treatment was found (risk increased by 9% (6%, 16%) per annum). No significant effect in terms of the type, the number or the serum level of the AEDs could be established. The head circumference of infants of epileptic mothers was significantly smaller (0.7 (1.2, 0.28 cm) compared to controls. An effect on the outcome of pregnancy of maternal folate supplementation or of folate blood concentrations during the periconceptional period and first trimester of pregnancy could not be determined. The severity of maternal epilepsy and/or AED treatment influences pregnancy outcome.


Obstetrics & Gynecology | 1999

Glutathione S-transferase isoenzymes in decidua and placenta of preeclamptic pregnancies

Petra L.M. Zusterzeel; Wilbert H.M. Peters; Marion A.H De Bruyn; Maarten F. C. M. Knapen; Hans M.W.M. Merkus; Eric A.P. Steegers

OBJECTIVE To investigate a possible involvement of glutathione S-transferases, major detoxificating enzymes, in the pathophysiology of preeclampsia. METHODS Levels of glutathione S-transferase isoforms and enzyme activity were assessed in placental and decidual tissues in 22 preeclamptic and 21 normotensive women. Measured values were analyzed statistically using the Mann-Whitney U test for comparison between groups, and the signed-rank test for comparison within groups. RESULTS Glutathione S-transferase pi is the main glutathione S-transferase isoform in normal placental and decidual tissue. Lower median placental and decidual glutathione S-transferase pi levels were found in preeclamptic women compared with controls: 1268 (range: 524-3925) and 2185 (range: 503-6578), P = .05, for placenta; 1543 (range: 681-2967) and 2169 (range: 893-3929), P = .02, for decidua. The total amount of glutathione S-transferases in control and preeclamptic pregnancies was higher in decidua than in placenta. CONCLUSION Reduced levels of glutathione S-transferase class pi in preeclampsia might indicate a decreased capacity of the glutathione/glutathione S-transferase detoxification system. A higher total amount of glutathione S-transferases in decidual tissue might point to a more pronounced protective role of decidua compared with placenta.


European Journal of Obstetrics & Gynecology and Reproductive Biology | 2003

Endometrial ablation by rollerball electrocoagulation compared to uterine balloon thermal ablation. Technical and safety aspects.

Ingrid A.A. van Zon-Rabelink; Michel P.H. Vleugels; Hans M.W.M. Merkus; Ruurd de Graaf

OBJECTIVE To compare two methods of endometrial ablation, hysteroscopic rollerball electrocoagulation (RBE) and non-hysteroscopic uterine balloon thermal (UBT) ablation (Thermachoice), regarding intra- and post-operative technical complications and safety aspects. STUDY DESIGN A randomised controlled study in a teaching hospital, 139 pre-menopausal women with dysfunctional uterine bleeding proved by a validated menstrual score list were enclosed. Endometrial ablation by a hysteroscopic or non-hysteroscopic method was performed. RESULTS Rollerball electrocoagulation carries a significantly higher risk of intra-operative complications compared to uterine balloon thermal ablation and is a significantly more time consuming procedure. Post-operative complication rates in both groups were low, but post-operative analgesics were prescribed significantly more in the uterine balloon group. CONCLUSION Endometrial ablation by uterine balloon thermal ablation (Thermachoice) is a safe and simple non-hysteroscopic procedure.


Annals of Clinical Biochemistry | 2003

Kinetics of myo-inositol loading in women of reproductive age.

Pascal M.W. Groenen; Hans M.W.M. Merkus; Fred C.G.J. Sweep; Ron A. Wevers; Fokje S.M. Janssen; Régine P.M. Steegers-Theunissen

Background: Myo-inositol plays a key role in an important intracellular signalling pathway. A deranged myo-inositol metabolism has been associated with neural tube defects. A myo-inositol loading test was performed to investigate the kinetics in healthy women of reproductive age. Methods: Five healthy non-obese females {mean age (standard deviation: SD) 22·8 (2·2) years} were recruited at the University Medical Center Nijmegen. Blood samples were drawn fasting and at 20, 40, 60, 90, 180 and 270 min after ingestion of 100 mg/kg body weight of myo-inositol. Urine samples were collected before myo-inositol loading and at 180 and 270 min post-loading. Samples were analysed for serum myo-, epi- and scyllo-inositol and glucose concentrations by gas chromatography. Plasma insulin concentrations were determined by radio-immunoassay. Random intercept models were fitted to evaluate the data. Results: The estimated myo-inositol and scyllo-inositol concentrations both reached maximum values at 180 min post-loading, respectively: mean (SD) 101·5 (9·2) µmol/L and 1·09 (0·11) µmol/L. The estimated plasma insulin and serum glucose concentrations decreased slightly but significantly during the experiment: P < 0·0001 and P < 0·05, respectively. At 180 and 270 min post-loading, urinary myo-inositol concentrations were increased and urinary glucose concentrations were unchanged. Conclusions: Myo-inositol enters the bloodstream quickly after oral ingestion and a small amount of myo-inositol is converted to scyllo-inositol. The synthesis of glucose from myo-inositol could not be detected by serum measurements. These data can be used in further research into the association between myo-inositol and neural tube defects.


Acta Obstetricia et Gynecologica Scandinavica | 2009

The Dutch Perinatal Audit Project: a feasibility study for nationwide perinatal audit in the Netherlands

Paul De Reu; Mariet Th. van Diem; Martine Eskes; Herman P. Oosterbaan; Luc Smits; Hans M.W.M. Merkus; Jan G. Nijhuis

Objective. To investigate the feasibility of nationwide perinatal mortality audits in the Netherlands. Study design. Over a one‐year period, data for all cases of perinatal mortality were collected. Six perinatal audit panels of professionals within perinatal care investigated and classified causes of death and identified the presence of substandard care factors (SSF). Results. Out of 22,189 newborns, 228 cases of perinatal mortality were audited. Placental pathology, congenital anomalies and preterm birth were the main causes of perinatal death. SSF by caregivers were identified in 72 cases (32 %). Almost 20% of the cases were not reported. Conclusions. In the Netherlands, perinatal audit is well supported by all groups of caregivers. It reveals usable facts and findings for the quality assessment of perinatal care. This audit showed that in 9% of the cases perinatal death was related to SSF and potentially avoidable. However, immediate reporting of cases of perinatal death apart from regular registration in the perinatal database proved to be inaccurate. Once a nationwide audit program is realized, in which data from the different caregivers will be collected in a single database instead of collection by linkage afterwards, this problem should be solved. Local audits will start from 2009. These audits will assess mortality cases within their respective areas and may initiate adjustments for perinatal care and optimize the quality of care and inter‐professional collaboration. Yearly nationwide audits will focus on specific items (e.g. term or post‐term deliveries) and may well offer an opportunity for the development or adjustment of national guidelines.


British Journal of Obstetrics and Gynaecology | 1998

Liver function following pregnancy complicated by the HELLP syndrome

Maarten F. C. M. Knapen; Anne M. van Altena; Wilbert H.M. Peters; Hans M.W.M. Merkus; Jan B.M.J. Jansen; Eric A.P. Steegers

Serum levels of aminotransferases, lactate dehydrogenase, gammaglutamyl transferase, alkaline phosphatase, albumin and conjugated bilirubin, measured in 54 women at a median of 31 months (range 3–101) after pregnancies complicated by the HELLP syndrome, were not elevated. Total bilirubin levels, however, were elevated in 20′1/0 of these women; this represents a significant difference from the prevalence in 151 women with a previous normal pregnancy (χ2= 12.23, P < 0.001), or in the normal female population (χ2= 22.34, P < 0.00001). This raises the possibility that a dysfunction of the bilirubin‐conjugating mechanism represents a risk factor for the development of the HELLP syndrome.

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Eric A.P. Steegers

Erasmus University Rotterdam

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Eva Maria Roes

Radboud University Nijmegen

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Arne M. van Heusden

Erasmus University Rotterdam

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Gerhard A. Zielhuis

Radboud University Nijmegen Medical Centre

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