Prolongation of progesterone supplementation in early pregnancy has no influence on the miscarriage rate, and thus no effect on the delivery rate. Progesterone supplementation can safely be withdrawn at the time of a positive HCG test.

L.H.T. received an unrestricted grant from Ferring Pharmaceuticals, Denmark, to support this study. P.H. received unrestricted research grants from MSD, Merck, Gedeon Richter and Ferring Pharmaceuticals outside of this work as well as honoraria for lectures from MSD, Merck and Gedeon Richter outside of this work. U.K. received honoraria for lectures from MSD and Ferring Pharmaceuticals outside of this work. C.A. received unrestricted research grants from MSD, IBSA, and Ferring Pharmaceuticals outside of this work as well as honoraria for lectures from MSD and IBSA. H.O.E. and B.B.P. received an unrestricted research grant from Gedeon Richter outside of this work. K.E., L.B., D.P. and B.H. have no conflict of interest. Furthermore, grants from 'The Health Research Fund of Central Denmark Region', 'The Research Foundation of the Hospital of Central Jutland', 'The Research Foundation of A.P. Møller', 'The Research Foundation of Aase & Ejnar Danielsen', 'The Research Foundation of Dagmar Marshall', 'The Research Foundation of Dir. Jacob Madsen & Hustru Olga Madsen', 'The Research Foundation of Fam. Hede Nielsen' and 'The Danish Medical Research Grant' supported conducting this study. The providers of funding were neither involved in the conduction of the study nor in the writing of the scientific report.

7th September 2010 DATE OF FIRST PATIENT'S ENROLMENT: 23rd November 2010.

Objective: To study whether endometrial scratching in the luteal phase before ovarian stimulation increases clinical pregnancy rates in women with one or more previous implantation failures. Design: A nonblinded multicenter randomized clinical trial. Setting: Fertility clinics. Patient(s): Three hundred four eligible patients scheduled for IVF/intracytoplasmic sperm injection were randomized. The intervention group (n ¼ 151) underwent endometrial scratching in the luteal phase before controlled ovarian stimulation, while no intervention was performed in the control group (n ¼ 153). Intervention(s): Endometrial scratching with a Pipelle de Cornier catheter in the luteal phase before ovarian stimulation. Main Outcome Measure(s): Clinical pregnancy rate and prenatal and birth data. Result(s): There was no overall significant improvement in clinical pregnancy rates between the control and intervention groups (38.5% vs. 44.4%; relative risk ¼ 1.15; confidence interval [0.86-1.55]). However, subgroup analyses revealed that women with three or more previous implantation failures had a significant increase in clinical pregnancy rate (31.1% vs. 53.6%; relative risk ¼ 1.72; confidence interval [1.05-2.83]) after scratching. No difference was seen as regards prenatal and birth data between the two groups. Conclusion(s): Endometrial scratching in the luteal phase before ovarian stimulation significantly enhances the clinical pregnancy rate in women with three or more prior implantation failures. This result seems to corroborate previous reports, which found that particularly women with repeated implantation failure seem to gain a positive effect from endometrial scratching. Importantly, there were no significant differences in prenatal data and birth data between the groups.

Zinc supplementation in pregnancy in a normal healthy middle class population in Denmark does not seem to offer any benefits to the mother or her fetus.