Related Experiment Video
Updated: Jul 18, 2026

Collection, Isolation, and Flow Cytometric Analysis of Human Endocervical Samples
Published on: July 6, 2014
Combined hormonal contraceptive trials: variable data collection and bleeding assessment methodologies influence
Daniel R Mishell1, John Guillebaud, Carolyn Westhoff
1Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. mishell@usc.edu
Abstract:
Initially approved for use in the United States nearly 50 years ago, oral hormonal contraceptives containing both estrogen and progestin have undergone steady improvements in safety and convenience. Concurrent with improvements in safety associated with decreasing doses of both steroids, there has been an increased incidence of unscheduled bleeding and spotting. There exist no standards regarding data collection techniques and methods, and reporting and analysis of bleeding and spotting events during combined hormonal contraceptive (CHC) trials. For the regulatory review of hormonal contraceptives, data regarding the incidence of bleeding and spotting events are not included in either of the traditional categories of efficacy and safety. Standardization of methods for collecting and analyzing data about cycle control in all clinical trials of CHCs is long overdue. Until such standards are developed and implemented, clinicians need to familiarize themselves with the techniques used in each study in order to provide correct information to their patients about the frequency of bleeding and spotting associated with different formulations and delivery systems.
Related Concept Videos
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Blinding
Blind Procedures
Bioequivalence Experimental Study Designs: Repeated Measures, Cross-Over, Carry-Over, and Latin Square Designs
Clinical Trials
There are four phases in a clinical trial. A phase one...
Hormonal Regulation of the Menstrual Cycle
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.