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Last Updated:
Jan 3rd, 2010 - 00:09:53
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Question
How accurate are fertility monitors and ovualtion monitors?
Niketta
Answer
Dear Niketta,
These devices measure the surge of the hormone LH (luteinizing hormone), which is secreted by the pituitary gland in the brain. LH plays a major role in triggering ovulation in the ovary. Generally, ovulation follows within 24 hours or so of the LH surge. The devices to which you refer are good at detecting LH, but 2 factors must also be considered. First, just because a woman has an LH surge, does not mean that she necessarily will ovulate. There are many abnormal situations (often found in women with fertility problems) where an ovulation either does not occur or occurs abnormally, such that an ovum (egg) is not produced, even though the woman had an LH surge. Thus, the LH devices measure a factor (namely, LH) which is involved indirectly, but not directly in fertility. This is in contrast, for example, to the measurement of cervical mucus, which is a factor directly involved in female fertility. Second, these devices are not at all effective for women wishing to avoid intercourse during the fertile time in order to avoid pregnancy. This is the case because a woman normally produces fertile cervical mucus for 5 to 7 days prior to ovulation. If intercourse occurs during the woman's mucus cycle, the sperm can easily survive for an extended period of time, waiting for ovulation to occur. The LH surge would only give a woman a day or so of lead time prior to ovulation--if she had intercourse prior to the LH surge, but at at time when she had fertile cervical mucus present, then she could get pregnant, even if she avoided intercourse after the "ovulation kit" was positive.
John Gisla, MD
John Gisla, MD, NFPMC is Board Certified by the American Academy of Family Physicians,
and Certified as a Medical Consultant for Natural Family Planning and NaPro Technology
by the Pope Paul VI Institute. He is on staff at Mercy of Folson Hospital and on the NFP Advisory
Board for the Diocese of Sacramento. He has been married ten years and has two daughters and a son.
© Copyright 2005 by CANFP
The information on this page and web site is for informational purposes only,
and is not a substitute for medical diagnosis and treatment by a physician.
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