Publications by authors named "F M Helmerhorst"

Background: Extensive evidence is available on hormonal contraceptive (HC) use and the risk of a first venous thromboembolism (VTE) event. Despite recommendations to discontinue combined HC (CHC) use, some women continue or start its use after a first VTE.

Objectives: We aimed to evaluate the VTE recurrence risk associated with HC use in premenopausal women.

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Background: Use of ethinylestradiol, one of the active ingredients in combined oral contraceptives, affects the incidence of venous thrombosis. To explain why some women develop thrombosis when using oral contraceptives and others do not, we hypothesized a role for the first-pass metabolism of ethinylestradiol in the liver. We set out to determine the association between genetic variation in the first-pass metabolism of ethinylestradiol, venous thrombosis risk and the effect on Sex-hormone-binding-globulin (SHBG) levels.

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In humans, the defective invasion of the maternal endometrium by fetal extravillous trophoblasts (EVTs) can lead to insufficient perfusion of the placenta, resulting in pregnancy complications that can put both mother and baby at risk. To study the invasion of maternal endometrium between (W)5.5-12 weeks of gestation by EVTs, we combined fluorescence in situ hybridization, immunofluorescence and immunohistochemistry to determine the presence of (male) EVTs in the vasculature of the maternal decidua.

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Aggression in patients with autism spectrum disorder (ASD) presents an important therapeutic challenge. Conventional treatment appears to be inadequate in a number of cases. The occurrence of severe aggressive symptoms since the inception of adolescence in a male patient with ASD suggested a hormonal influence by androgens.

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Background: Progestin-only contraceptives (POCs) are appropriate for many women who cannot or should not take estrogen. POCs include injectables, intrauterine contraception, implants, and oral contraceptives. Many POCs are long-acting, cost-effective methods of preventing pregnancy.

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