Des chercheurs canadiens ont prouvé que l'ovulation ne se faisait pas systematiquement au milieu du cycle...
Research Proves Ovulation Can Occur at Almost Any Point in Monthly Cycle
Waves in female fertility cycle
Conventional wisdom about the female menstrual cycle and when a woman is able to reproduce was turned upside down in 2003 with the release of a study by a research team at the University of Saskatchewan.
The team, led by Dr. Roger Pierson, discovered there is more than one "wave" or peak period during the menstrual cycle when the follicles in a woman's ovaries prepare themselves to release an egg. Dr. Pierson's research showed that women can have two or three such peak waves per cycle. During one of these peaks, one follicle will become dominant and release an egg that could be fertilized and result in pregnancy.
This means a woman can become pregnant at any time during her menstrual cycle, depending on the timing of these waves and which one leads to the development of a mature follicle and release of an egg. Previously, medical experts believed there was only one such wave during the 28-day menstrual cycle, resulting in an egg ready for fertilization on about day 14 of the cycle.
"The study shows that we have not fully understood the basic biological processes that occur during menstrual cycles. We are literally going to have to rewrite medical textbooks," Dr. Pierson said.
The discovery has major implications in the field of reproductive research both in helping women who have difficulties in conceiving and in preventing unwanted pregnancies. Discover magazine ranked the results among the top 100 science stories of 2003. As well, Dr. Pierson, who is the head of the university's Reproductive Biology Research Unit, received the 2003 Women's Health Hero Award from Chatelaine magazine for the research work.
In their ground-breaking study, the University of Saskatchewan researchers performed ultrasound imaging on a group of 63 women, who ranged in age from 18 to 40, every day for six weeks. Thanks to the intensive research work and commitment of the women volunteers, the researchers obtained a more complete picture of activities in a woman's ovaries over a full menstrual cycle than ever before.
Key contributors to the research included Dr. Angela Baerwald, a University of Saskatchewan doctoral student, and Dr. Gregg Adams, a veterinarian and professor with the university's Western College of Veterinary Medicine. Dr. Adams and Dr. Pierson had previously collaborated on similar research with cows and horses and discovered that these animals also had more than one wave of follicle development in their reproductive cycles.
Some birth control pills deliver high levels of hormones around Day 14 and taper off near the end of the cycle, which could lead to pregnancy if ovulation occurs at the end of the cycle. As well, some forms of assisted reproductive technologies to help women conceive may not be as effective if they depend on the old model of one possible window for ovulation.
Research Proves Ovulation Can Occur at Almost Any Point in Monthly Cycle
Waves in female fertility cycle
Conventional wisdom about the female menstrual cycle and when a woman is able to reproduce was turned upside down in 2003 with the release of a study by a research team at the University of Saskatchewan.
The team, led by Dr. Roger Pierson, discovered there is more than one "wave" or peak period during the menstrual cycle when the follicles in a woman's ovaries prepare themselves to release an egg. Dr. Pierson's research showed that women can have two or three such peak waves per cycle. During one of these peaks, one follicle will become dominant and release an egg that could be fertilized and result in pregnancy.
This means a woman can become pregnant at any time during her menstrual cycle, depending on the timing of these waves and which one leads to the development of a mature follicle and release of an egg. Previously, medical experts believed there was only one such wave during the 28-day menstrual cycle, resulting in an egg ready for fertilization on about day 14 of the cycle.
"The study shows that we have not fully understood the basic biological processes that occur during menstrual cycles. We are literally going to have to rewrite medical textbooks," Dr. Pierson said.
The discovery has major implications in the field of reproductive research both in helping women who have difficulties in conceiving and in preventing unwanted pregnancies. Discover magazine ranked the results among the top 100 science stories of 2003. As well, Dr. Pierson, who is the head of the university's Reproductive Biology Research Unit, received the 2003 Women's Health Hero Award from Chatelaine magazine for the research work.
In their ground-breaking study, the University of Saskatchewan researchers performed ultrasound imaging on a group of 63 women, who ranged in age from 18 to 40, every day for six weeks. Thanks to the intensive research work and commitment of the women volunteers, the researchers obtained a more complete picture of activities in a woman's ovaries over a full menstrual cycle than ever before.
Key contributors to the research included Dr. Angela Baerwald, a University of Saskatchewan doctoral student, and Dr. Gregg Adams, a veterinarian and professor with the university's Western College of Veterinary Medicine. Dr. Adams and Dr. Pierson had previously collaborated on similar research with cows and horses and discovered that these animals also had more than one wave of follicle development in their reproductive cycles.
Some birth control pills deliver high levels of hormones around Day 14 and taper off near the end of the cycle, which could lead to pregnancy if ovulation occurs at the end of the cycle. As well, some forms of assisted reproductive technologies to help women conceive may not be as effective if they depend on the old model of one possible window for ovulation.
