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Biomedical subjects

J M Merkus

Publications and source records attributed to J M Merkus.

At least 19 recordsLinked to original sources
PubMed2001

The Perinatal Database of the Netherlands.

OBJECTIVE: In the Netherlands, the Perinatal Database of the Netherlands (Landelijke Verloskunderegistratie, LVR) was set up in 1982 for secondary care obstetric departments on a voluntary participation basis, its main goal being quality monitoring. At the outset of the database, 70% of Dutch obstetric departments participated immediately. This percentage has now increased to almost 100%. How the LVR was set up, its aims, participation, general function and some aspects of the reliability are described in this article. RESULTS: Assessment of the reliability of the data on a number of points found that the frequency of various types of nearly all errors has decreased during the existence of the LVR, with the exception of a complete registration of the first-week mortality. CONCLUSIONS: The quality of the data has improved over the years. More reliable figures for the first-week mortality would be available if the LVR data were linked to those of the Neonatal Database of the Netherlands (Landelijk Neonatale Registratie, LNR), so that the condition of each child is known up to and including 28 days after birth. Improvements in the reliability of other items can be attained by implementing more checks during the data input stage and by making the data more accessible to the gynaecologists, in order to further increase motivation to record the data.

Cesarean Section↗
PubMed2001

Dynamics of immunoreactive endothelin plasma levels during ovarian stimulation for in vitro fertilization with and without dietary sodium restriction.

OBJECTIVE: To investigate the correlation between immunoreactive endothelin plasma levels and both the number and size of follicles and its relationship with the development of ovarian hyperstimulation syndrome, in in vitro fertilization cycles, with and without dietary sodium restriction. STUDY DESIGN: Randomized study in an assisted reproduction unit of a large teaching hospital. Data of 88 women form the basis of this report (45 ad libitum sodium intake and 43 dietary sodium restriction). Non-parametric tests were used for statistical analysis. RESULTS: Immunoreactive endothelin plasma levels neither correlate with the number of follicles, independent of their size, nor with the grade of ovarian hyperstimulation syndrome. Immunoreactive endothelin plasma levels decrease significantly in the luteal phase. These results are the same in both sodium diet groups. CONCLUSIONS: Immunoreactive endothelin plasma levels do not correlate with the number and size of follicles and they are not related to the development of ovarian hyperstimulation syndrome. These findings are independent of sodium intake.

Diet, Sodium-Restricted↗
PubMed2000

Male factor subfertility: possible causes and the impact of nutritional factors.

OBJECTIVE: To review possible causes for male factor subfertility with emphasis on nutritional factors such as zinc and folate. DESIGN: A literature search was performed on MEDLINE and via bibliographies of published works. RESULT(S): Many causes for male factor subfertility are described in the literature. Both environmental and genetic factors could play a role. However, the pathogenesis of male factor infertility is poorly understood, including the role of specific micronutrients such as zinc and folate. Both zinc and folate are involved in the synthesis of DNA and RNA. Despite the fact that zinc deficiency leads to several clinical symptoms such as decreased spermatogenesis and impaired male fertility, the exact pathophysiology has not been clarified. CONCLUSION(S): Because most causes of male factor subfertility are unknown, more research is needed. Because male factor subfertility due to nutritional deficiencies is in principle amenable to curative and/or preventive action by supplementation, emphasis should be put on studies on the effect of specific nutrients on male fertility.

Age Factors↗
PubMed1999

[Discordant fetal growth in multiple pregnancy: intervention should be based on chorionicity].

In three women, aged 28, 35, and 38 years, with multiple pregnancies and discordant foetal growth, the question arose what to do in case of (threatening) intrauterine death of one twin. In one monochorionic pregnancy with single foetal death the survivor suffered irreversible neurological damage and died at the age of five months, in one monochorionic pregnancy the survivor was born healthy and in one dichorionic pregnancy both twins were born healthy although one twin showed severe intrauterine growth retardation. The problem concerning single foetal death in a monochorionic pregnancy is whether to terminate the pregnancy and accept the risk of premature birth to the surviving twin, or to continue the pregnancy and accept the risk of damage to the survivor. In a dichorionic pregnancy foetal death of one twin does not entail any great risk of damage to the survivor; in such a pregnancy single foetal death in a premature phase may be accepted and the pregnancy may be continued. Sonographic determination of the chorionicity in multiple pregnancy at an early stage is essential because it also determines the policy if foetal problems occur.

Adult↗
PubMed1999

['Authority-based' versus 'evidence-based' blood pressure measurements in pregnancy].

Recent evidence suggests that the fifth Korotkoff sound (K5) is a much more reliable point of measurement to determine diastolic blood pressure in pregnant women than the fourth one (K4). The guidelines for obstetricians and midwives should be corrected without delay to reflect this new knowledge. In non-pregnant people K5 already is the point of reference.

Adult↗
PubMed1999

Leiomyomatosis peritonealis disseminata: does malignant transformation occur? A literature review.

Leiomyomatosis peritonealis disseminata (LPD) is a rare smooth muscle tumor. In the literature more than 100 cases have been described. LPD is characterized by multiple small nodules on the peritoneal surface, mimicking a malignant process with metastases, but generally demonstrates benign histologic features. Exposure to estrogen seems to play an etiologic role. Many patients have uterine leiomyomas as well. The diagnosis of LPD is easily made on biopsy. Reduction of estrogen exposure is generally sufficient to cause regression of LPD. Surgical castration or gonadotrophin releasing hormone agonists seem good alternatives in the case of progression or recurrence of LPD. In six patients a malignant leiomyosarcoma has been described shortly after the diagnosis of LPD was made. Five of these patients did not have uterine leiomyomas or exposure to exogenous or increased endogenous estrogen. The relationship with pregnancy in the sixth patient may be coincidental. Whether malignant transformation of LPD occurs remains uncertain. Characteristics of these patients differ from those of LPD patients and may indicate a high malignant potential, necessitating a different approach.

Adult↗
PubMed1999

Sodium-blood pressure interrelationship in pregnancy.

In non-pregnant individuals, a strong positive association of sodium intake with blood pressure has been established, but the relationship between sodium intake and blood pressure in human pregnancy remains obscure up to date. The aim of this prospective observational cohort study was to assess the relationship between urinary sodium excretion (as a measure for intake) and blood pressure from the early second trimester onwards throughout pregnancy. The study group consisted of 667 low-risk women with singleton pregnancies, of whom 350 were nulliparous and 317 parous. Blood pressure was measured in a standardised fashion at predetermined intervals from the first antenatal visit prior to 16 weeks gestation until delivery. Urinary sodium excretion was measured in 24-h urine collections on at least four occasions between 16 and 38 weeks gestation. Main outcome measures were the coefficients of correlation between changes in urinary sodium output and changes in blood pressure during six different gestational epochs. No significant correlations were found between changes in urinary sodium output and changes in blood pressure. Correlation coefficients were alike for nulliparous and parous women and for different gestational intervals. Prior to 32 weeks gestation, no differences were observed in sodium excretion between women who remained normotensive and those who developed gestational hypertension. These results suggest that changes in sodium intake are not associated with blood pressure changes in low-risk pregnant women. Blood pressure increases as observed in the second half of normotensive and hypertensive pregnancies are unlikely to be caused by changes in renal sodium handling.

Adult↗
PubMed1999

Female sex hormone replacement therapy increases serum free 1,25-dihydroxyvitamin D3: a 1-year prospective study.

OBJECTIVE: Currently, hormone replacement therapy is applied successfully to reduce post-menopausal bone resorption. However, the exact mechanism by which oestrogen exerts its effect has not yet been fully elucidated. In order to determine whether changes in the biologically active 1,25-dihydroxyvitamin D3 may be of importance in this process, the concentrations of both total and free 1,25-dihydroxyvitamin D3 in serum were assessed. DESIGN: In 36 post-menopausal women the effect of hormone replacement therapy, with a combination of 17 beta-oestradiol and norethisterone acetate, on the serum levels of total and free 1,25-dihydroxyvitamin D3 was studied after 0, 3, 6 and 12 cycles. MEASUREMENTS: The total concentration of 1,25-dihydroxyvitamin D3 in serum was assessed using a radioreceptor assay after diethylether extraction of the samples followed by paper chromatography. The free fraction of 1,25-dihydroxyvitamin D3 was measured using symmetric dialysis. The free 1,25 dihydroxyvitamin D3 concentration was calculated by multiplying the total concentration by the free fraction. RESULTS: During therapy, mean serum total 1,25-dihydroxyvitamin D3 concentrations (+/- SD) were 106.4 pmol/l (+/- 27.5), 155.0 pmol/l (+/- 49.5), 176.7 pmol/l (+/- 70.0) and 161.1 pmol/l (+/- 55.3) at 0, 3, 6 and 12 cycles, respectively. Serum free 1,25-dihydroxyvitamin D3 concentrations were 68 fmol/l (+/- 22), 107 fmol/l (+/- 35), 120 fmol/l (+/- 43) and 108 fmol/l (+/- 37), respectively. Baseline values of both total and free 1,25-dihydroxyvitamin D3 were significantly lower than those during therapy at all time (P < or = 0.001). CONCLUSION: Both the serum total 1,25-dihydroxyvitamin D3 and the serum free 1,25-dihydroxyvitamin D3 concentrations are increased during combined 17 beta-oestradiol and norethisterone acetate therapy for a year. Assuming that the free concentration 1,25-dihydroxyvitamin D3 reflects the biologically active fraction, this rise may in part explain the preventive effect of hormone replacement therapy on osteoporosis.

Calcitriol↗
PubMed1998

[Multiples births: a continuing problem with assisted reproductive techniques].

Assisted reproductive techniques (ART) such as in vitro fertilisation (IVF), ovulation induction and superovulation followed by insemination have caused a sharp increase in multiple birth prevalence rates. The perinatal morbidity of multiple birth infants is high because of the high incidence of premature birth. The social and psychological problems of multiple birth families are also considerable. In 1990 high-order multiple births were mainly the result of IVF. Although the number of IVF treatments has increased more than the number of other ART treatments, nowadays high-order multiple births are predominantly caused by superovulation. Since 1990 the number of high-order multiple births has stabilised, but the recent sharp increase in ART twins results in a further rise in births of severely preterm ART infants. More restraint should be practised in superovulation treatments to bring down the number of (high-order) multiple births.

Adult↗
PubMed1998

[The indispensable anamnesis: in-vitro fertilization in a woman under treatment for melanoma].

A couple consulted the gynaecologist repeatedly because of a primary fertility disorder. When they had desired children for 8 years, no pregnancy had yet occurred. In-vitro fertilization (IVF) treatment was started. A few days after the beginning of the hormonal treatment that precedes the IVF procedure, the woman noted a swelling in the right inguinal area for which she consulted the surgeon. This swelling was found to be a metastasis of a melanoma that had been removed from her leg 6 months previously. The gynaecologist was not aware of this case history and the surgeon was not informed of the started IVF treatment. As was found later, this was in accordance with the couple's wishes. The first IVF treatment resulted in a pregnancy that ended with the birth of a healthy boy. The placenta showed melanomatous metastases and the mother died 2 months after the birth of her son.

Adult↗
PubMed1998

[Melanoma in pregnancy].

The incidence of pregnancy complicated by melanoma of the skin, calculated from data of the Netherlands Cancer Registry, is 1 per 10,000 pregnancies. The prognosis of a melanoma is not affected by prior or subsequent pregnancy. A melanoma diagnosed during pregnancy does appear to have a more unfavourable prognosis, due not to a less favourable clinical course, but to a delay in diagnosing melanoma during pregnancy and (or) a less favourable site. When a pregnancy is complicated by malignancy, in case of a melanoma there is a higher risk of placental metastasis compared with other malignancies. In nearly 50% of the cases reported in literature of placental metastasis there was foetal involvement.

Adult↗
PubMed1998

[Preconception counseling in family practice; a survey of 100 family physicians].

OBJECTIVE: To assess the awareness, opinions on desirability and preconditions such as special knowledge with regard to the concept of preconceptional health counselling among general practitioners. DESIGN: Descriptive. SETTING: General practices in the Groot Gelre district of the Dutch General Practitioners Society. METHOD: A representative sample of 100 general practitioners were asked by phone for permission to send a questionnaire; 89 out of the 94 general practitioners who were sent a questionnaire replied (response: 89%). RESULTS: Almost all general practitioners (88%) knew about the concept of preconceptional health counselling and most of them already gave some kind of preconceptional advice. 93% considered preconceptional health counselling part of their job responsibility and 91% were prepared to give more preconceptional health care in the future. 53% of all general practitioners, however, indicated that they lacked sufficient knowledge to give adequate advice. The advantages of preconceptional health care were considered to outweigh possible disadvantages such as medicalization of pregnancy. CONCLUSION: The general practitioners knew about preconceptional health care and considered it part of their job. Many already provided preconceptional health care, although not in a structured way. General practitioners appeared to lack time and appropriate knowledge, which indicates a need for postgraduate training.

Data Collection↗
PubMed1998

Ovarian hyperstimulation syndrome: facts and fallacies.

Severe or critical ovarian hyperstimulation syndrome (OHSS) is a serious complication of ovarian hyperstimulation for assisted reproduction techniques (ART). The syndrome is characterized by cystic enlargement of the ovaries and fluid shifts from the intravascular to the third space. The morbidity in OHSS is mainly determined by the hemodynamic changes caused by increased capillary permeability. The incidence of OHSS depends on definitions, risk factors, ovarian stimulation protocols, luteal support and conception. Currently, research on the pathogenesis of OHSS is focused on increased capillary permeability. Several theories are reviewed. Until the pathogenesis of OHSS becomes clear, treatment is restricted to supportive therapy. The various proposals for management of OHSS are discussed and, based on the available data, directions for the management of various grades of OHSS are summarized. However, prevention and early recognition are still the most important tools to handle OHSS. A flowchart with preventive measures for OHSS is presented derived from the available literature.

Algorithms↗
PubMed1996

Randomised comparison between a loading and incremental dose model for ritodrine administration in preterm labour.

OBJECTIVE: To compare a new loading dose regimen for intravenous ritodrine administration in preterm labour with the conventional dose regimen. DESIGN: Multicentre randomised trial using numbered opaque sealed envelopes. SETTING: Five teaching hospitals in the Netherlands. PARTICIPANTS: Women (n = 203) in preterm labour at less than 34 weeks of gestation. INTERVENTIONS: Women received either a loading dose ritodrine infusion followed, as soon as tocolysis was reached, by a decrease in infusion rate or the conventional schedule of increasing doses until uterine quiescence was achieved. RESULTS: Frequency of successful tocolysis (71%) and duration of treatment (55 h) were similar in both groups, but the loading dose schedule was better tolerated with fewer adverse events. Also the number of dose adjustments was smaller than in the incremental dose group (P < 0.001). Overall, the differences between the two regimens were unexpectedly small. CONCLUSIONS: Despite the small differences, the loading model is easier to apply, requires fewer dose adjustments, is better tolerated with less side effects, and reduces the likelihood of clinical error.

Dose-Response Relationship, Drug↗
PubMed1996

Double-blind evaluation of ritodrine sustained release for oral maintenance of tocolysis after active preterm labour.

OBJECTIVE: To evaluate the effect of ritodrine sustained release capsules for maintaining uterine quiescence after successful treatment of active preterm labour. DESIGN: Multicentre placebo-controlled trial. SETTING: Five teaching hospitals in the Netherlands. PARTICIPANTS: Women (n = 95) at less than 35 weeks of gestation in whom active preterm labour had been stopped with intravenous ritodrine. INTERVENTIONS: Women received either two 40 mg ritodrine sustained release capsules (n = 50) or identical placebo capsules (n = 45) three times a day for seven days. RESULTS: The proportion of women who received another course of active treatment was significantly smaller with the sustained release than with placebo (1 of 50 versus 11 of 45: P = 0.003) as was the number delivering because of preterm labour during treatment (0 of 50 versus 4 of 45: P = 0.04). There were no other significant differences between the two groups. CONCLUSIONS: Maintenance treatment with ritodrine sustained release capsules after arrest of preterm labour reduces the risk of recurrences of preterm labour that necessitate treatment or precipitate delivery.

Administration, Oral↗