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Featured researches published by Helen Klip.


The Lancet | 2002

Hypospadias in sons of women exposed to diethylstilbestrol in utero : a cohort study

Helen Klip; Janneke Verloop; Jan D. Van Gool; Marlies E. T. A. Koster; Curt W. Burger; Flora E. van Leeuwen

BACKGROUND Transgenerational effects of diethylstilbestrol (DES) have been reported in animals, but effects in human beings are unknown. Alerted by two case reports, we aimed to establish the risk of hypospadias in the sons of women who were exposed to DES in utero. METHODS We did a cohort study of all sons of a Dutch cohort of 16284 women with a diagnosis of fertility problems. We used a mailed questionnaire assessing late effects of fertility treatment to identify boys with hypospadias. We compared the prevalence rate of hypospadias between boys with and without maternal DES exposure in utero. FINDINGS 16284 mothers (response rate 67%) reported 8934 sons. The mothers of 205 boys reported DES exposure in utero. Four of these children were reported to have hypospadias. In the remaining 8729 children, only eight cases of hypospadias were reported (prevalence ratio 21.3 [95% CI 6.5-70.1]). All cases of hypospadias were medically confirmed. Maternal age or fertility treatment did not affect the risk of hypospadias. Children conceived after assisted reproductive techniques such as in-vitro fertilisation were not at increased risk of hypospadias compared with children conceived naturally (1.8, 0.6-5.7). INTERPRETATION Our findings suggest an increased risk of hypospadias in the sons of women exposed to DES in utero. Although the absolute risk of this anomaly is small, this transgenerational effect of DES warrants additional studies.


Fertility and Sterility | 2002

A low number of retrieved oocytes at in vitro fertilization treatment is predictive of early menopause

Evelien J. de Boer; Isolde Den Tonkelaar; B. Egbert R. Te Velde; Curt W. Burger; Helen Klip; Flora E. van Leeuwen

OBJECTIVE To investigate whether women with a low number of retrieved oocytes at the first in vitro fertilization (IVF) attempt have an increased risk of early menopause. DESIGN Nested case-control study. SETTING Twelve IVF clinics in the Netherlands. PATIENT(S) Women participating in a nationwide Dutch cohort study (OMEGA) of ovarian stimulation for IVF and subsequent gynecologic diseases (n = 26,428). Each patient who experienced natural menopause at or before 46 years (n = 38) was individually matched to five controls (n = 190) who had not yet entered menopause at the age the patient became postmenopausal. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Relative risk of reaching natural menopause at an early age (</=46 years), according to the number of retrieved oocytes at the first IVF attempt. RESULT(S) Women with a poor response (zero to three oocytes) had a relative risk of 11.6 (95% confidence interval: 3.9-34.7) of having an early menopause as compared with women who have a normal response (> three oocytes). Women who were stimulated with gonadotropins during IVF treatment but did not undergo an IVF puncture because of an anticipated poor response (canceled IVF cycle) had a relative risk of 8.3 (95% confidence interval: 2.9-23.9). CONCLUSION These results suggest that women with a low number of retrieved oocytes at the first IVF treatment are more likely to become postmenopausal at an early age than women with a higher number of retrieved oocytes. Our study is the first longitudinal study to provide strong evidence for the quantitative aspect of the ovarian concept of reproductive aging.


Cancer Causes & Control | 2000

Cancer Risk Associated with Subfertility and Ovulation Induction: A Review

Helen Klip; Curt W. Burger; Peter Kenemans M.D.; Flora E. van Leeuwen

AbstractObjective: Over the past decades the use of fertility drugs (FDs) has greatly increased. Recently, the possible association between the use of FDs and risk of cancer has aroused great concern. In this paper, we critically review the available epidemiologic studies. Methods: We identified papers published between 1966 and 1999 that examined FDs and specific causes of subfertility in relation to the risks of cancers of the ovary, breast, endometrium and thyroid, and melanoma. Results: Although present insights into the pathogenesis of hormone-related malignancies suggest a possible association between the use of FDs and the risk of specific cancers, this has not been convincingly demonstrated in epidemiologic studies. With regard to cancer risk in relation to the cause of subfertility, the only consistent association observed is an increased risk of endometrial cancer for women with subfertility due to hormonal disorders. While positive findings in some studies on FDs and ovarian cancer risk have aroused serious concern, the associations observed in most of these reports appear to be due to bias or chance rather than being causal. The most important sources of bias are inadequate confounder control for both parity and causes of subfertility. Conclusions: To discriminate between the possible carcinogenic effects of various ovulation induction regimens, subfertility disorders, and reproductive characteristics associated with subfertility, future studies should include large populations of subfertile women with sufficient follow-up time. In such cohort studies the cause of subfertility should be measured adequately (based on medical records) and information about reproductive characteristics should be collected for all cohort members. Such studies should also include a group of subfertile women with an indication for FD use but not so treated.


Human Reproduction | 2011

Risk of borderline and invasive ovarian tumours after ovarian stimulation for in vitro fertilization in a large Dutch cohort

F.E. van Leeuwen; Helen Klip; T.M. Mooij; A.M.G. Van de Swaluw; Cornelis B. Lambalk; M. Kortman; Joop S.E. Laven; C.A.M. Jansen; Frans M. Helmerhorst; B.J. Cohlen; Wim N.P. Willemsen; J.M.J. Smeenk; Arnold Simons; F. van der Veen; Johannes L.H. Evers; P.A. van Dop; Nick S. Macklon; Curt W. Burger

BACKGROUND Long-term effects of ovarian stimulation for IVF on the risk of ovarian malignancies are unknown. METHODS We identified a nationwide historic cohort of 19 146 women who received IVF treatment in the Netherlands between 1983 and 1995, and a comparison group of 6006 subfertile women not treated with IVF. In 1997–1999, data on reproductive risk factors were obtained from 65% of women and data on subfertility (treatment) were obtained from the medical records. The incidence of ovarian malignancies (including borderline ovarian tumours) through 2007 was assessed through linkage with disease registries. The risk of ovarian malignancies in the IVF group was compared with risks in the general population and the subfertile comparison group. RESULTS After a median follow-up of 14.7 years, the risk of borderline ovarian tumours was increased in the IVF group compared with the general population [standardized incidence ratio (SIR) = 1.76; 95% confidence interval (CI) = 1.16–2.56]. The overall SIR for invasive ovarian cancer was not significantly elevated, but increased with longer follow-up after first IVF (P = 0.02); the SIR was 3.54 (95% CI = 1.62–6.72) after 15 years. The risks of borderline ovarian tumours and of all ovarian malignancies combined in the IVF group were significantly increased compared with risks in the subfertile comparison group (hazard ratios = 4.23; 95% CI = 1.25–14.33 and 2.14; 95% CI = 1.07–4.25, respectively, adjusted for age, parity and subfertility cause). CONCLUSIONS Ovarian stimulation for IVF may increase the risk of ovarian malignancies, especially borderline ovarian tumours. More large cohort studies are needed to confirm these findings and to examine the effect of IVF treatment characteristics.


Human Reproduction | 2011

The addition of GnRH antagonists in intrauterine insemination cycles with mild ovarian hyperstimulation does not increase live birth rates—a randomized, double-blinded, placebo-controlled trial

A.E.P. Cantineau; B.J. Cohlen; Helen Klip; Maas Jan Heineman; Annemieke Hoek; C.B. Lambalk; C.J.C.M. Hamilton; P.F. van Bommel; P.A. van Dop; P.F.M. van der Heijden; P. De Sutter; Thomas D'Hooghe; Petra A. P. Manger; Willem Ombelet; J.G. Santema

BACKGROUND This multicenter, double-blinded RCT investigated the efficacy of GnRH antagonists in cycles with mild ovarian hyperstimulation (MOH) followed by IUI in subfertile women. METHODS Couples diagnosed with unexplained, male factor subfertility or associated with the presence of minimal or mild endometriosis were randomized with a computer-generated list of numbers by a third party in a double-blinded setting to receive either a GnRH antagonists or a placebo in 12 institutional or academic hospitals. All women were treated with recombinant FSH in a low-dose step-up regimen starting on Day 2-4 of the cycle. A GnRH antagonist was added when one or more follicles of 14 mm diameter or more were visualized. When at least one follicle reached a size of ≥18 mm, ovulation was induced by hCG injection. A single IUI was performed 38-40 h later. Couples were offered a maximum of three consecutive cycles. The primary outcome of the trial was live births. Secondary outcomes were pregnancy rates, multiple pregnancy rates, miscarriages and ovarian hyperstimulation syndrome rate. RESULTS A total of 233 couples were included from January 2006 to February 2009, starting 572 treatment cycles. Live birth rates were not significantly different between the group treated with GnRH antagonist (8.4%; 23/275) and the placebo group (12%; 36/297) (P = 0.30). Three twin pregnancies occurred in the GnRH antagonist group and two twin pregnancies in the placebo group. CONCLUSIONS Adding a GnRH antagonist in cycles with MOH in an IUI program does not increase live birth rates. Dutch Trial Register no: NTR497.


Human Reproduction | 2001

Risk of cancer in the offspring of women who underwent ovarian stimulation for IVF

Helen Klip; Curt W. Burger; Jan de Kraker; Flora E. van Leeuwen


Human Reproduction | 2003

Risk of benign gynaecological diseases and hormonal disorders according to responsiveness to ovarian stimulation in IVF: a follow-up study of 8714 women

Helen Klip; F.E. van Leeuwen; R. Schats; C.W. Burger


Fertility and Sterility | 2008

Risk of borderline and invasive ovarian tumors after ovarian stimulation for in vitro fertilization in a large Dutch cohort

F.E. van Leeuwen; Helen Klip; T.M. Mooij; A.M.G. Van de Swaluw; C.W. Burger


Archive | 2003

Oncogenic risks related to assisted reproductive technologies

P van Dop; Helen Klip; C. W. Burger


Paediatric and Perinatal Epidemiology | 2001

Increased risk of hypospadias in male offspring of women exposed to diethylstilbestrol in utero

Helen Klip; Janneke Verloop; J van Gool; Meta Koster; C.W. Burger; Fe van Leeuwen

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Curt W. Burger

Erasmus University Rotterdam

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C.W. Burger

Netherlands Cancer Institute

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Flora E. van Leeuwen

Netherlands Cancer Institute

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F.E. van Leeuwen

Netherlands Cancer Institute

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A.M.G. Van de Swaluw

Netherlands Cancer Institute

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B.J. Cohlen

Erasmus University Rotterdam

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Janneke Verloop

Netherlands Cancer Institute

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T.M. Mooij

Netherlands Cancer Institute

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A.E.P. Cantineau

University Medical Center Groningen

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Annemieke Hoek

University Medical Center Groningen

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