Triphasic Pattern and Pregnancy: a Statistical Analysis
Introduction: When charting for
pregnancy achievement, there is great interest in identifying early
signs which may indicate whether or not there is an increased
probability of pregnancy in a given cycle. There has been speculation
and much anecdotal evidence to suggest a relationship between a
triphasic chart pattern and an increased probability of pregnancy,
but until now, no large-scale statistical analysis has been done to
determine whether or not this is the case.
Objective: Our main goal for this study
is to determine whether or not a triphasic pattern occurs more
frequently on pregnancy charts than on non-pregnancy charts.
Definition of Triphasic Pattern: For
the purpose of this study, a triphasic pattern is defined as a
sustained "third level" of higher temperatures beginning
at least seven days after the ovulation rise. We used the
pattern here exactly as identified by Fertility Friend's
software. In the rest of this
article we will refer to the triphasic pattern in the context
mentioned here. Other ways of identifying the pattern may lead to
different results. The advantage of our system is that it is an
automated procedure and is not subject to human appreciation and its
Triphasic Illustration: For
illustration purposes, see the triphasic chart below:
Method: We considered a batch of the
most recent charts analyzed on the FertilityFriend.com web site.
149,781 recent charts were considered.
For each chart considered we took note of the
the ovulation day
whether or not a triphasic pattern was
which day after ovulation a triphasic pattern
pregnancy test results
We did not consider any chart for which no
intercourse during the fertile window was recorded. In other words,
all charts considered had a chance to result in pregnancy.
We measured the frequency of the occurrence of
the triphasic pattern in our sample for both pregnancy charts and
charts not leading to a pregnancy.
Frequency of a Triphasic Pattern for
Frequency of a Triphasic Pattern for
Average Days Past Ovulation (DPO) when this
Discussion: The results show that the
triphasic pattern indeed occurs more frequently on pregnancy charts.
Especially interesting are the following results:
The magnitude of
the difference is quite significant. This pattern is 179% more frequent on pregnancy charts.
The moment in the cycle at which this pattern
is the most likely to occur is nine days past ovulation. This is
within the window of the most likely time for implantation. (Wilcox,
A. J., D. D. Baird, et al.1999).
Although the pattern occurs with greater
frequency on pregnancy charts, most pregnancy charts do not show
this pattern. While it is a good sign when you are hoping for
pregnancy, you do not need this pattern to be pregnant.
Seeing this pattern does not guarantee or confirm pregnancy. While the probability of pregnancy is increased significantly when you see this pattern, it also occurs on non-pregnant charts and so cannot confirm pregnancy before a pregnancy test can be reliably taken.
What exactly causes this pattern to occur more frequently
on pregnancy charts is not definitively known. The most likely possibility is that increased
progesterone in pregnancy cycles plays a role in causing this pattern. This is because progesterone raises
temperatures and progesterone levels have been found to be higher in
pregnancy cycles than in non-pregnancy cycles (Baird,
D. D., C. R. Weinberg, et al. 2003). As the pattern occurs
around implantation time, there may also be some relationship between
this pattern and the production of the pregnancy hormone, hCG, which
begins to be produced at this time, or the related rescue of the
corpus luteum, which also happens at this time in pregnancy cycles
(Baird, D. D., C. R. Weinberg, et al. 2003). Instead of regressing as it does in non-conception cycles, the corpus luteum is "rescued" at implantation time and continues to produce progesterone, often at elevated levels, during early pregnancy in conception cycles (Baird, D. D., C. R. Weinberg, et al. 2003).
Although these results confirm that the triphasic
pattern is indeed a possible early pregnancy sign it also shows that it is
not an absolute sign either as the pattern also appears on
non-pregnant charts. In practical terms this means that seeing this
pattern on your chart is indeed a good sign but it is not an
assurance that you will be pregnant. Not seeing the pattern on your
chart is likewise not an indication that you are not pregnant. It is also important to recognize that there are a variety of other factors that may influence the probability of pregnancy in any cycle. As
usual we recommend that you follow the pregnancy test recommendation
given by the Fertility Friend pregnancy
References: Baird, D. D., C. R. Weinberg,
et al. (2003). "Rescue of the corpus luteum in human pregnancy."
Biol Reprod68(2): 448-56.
Wilcox, A. J., D. D. Baird, et
al. (1999). "Time of implantation of the conceptus and loss of
pregnancy." N Engl J Med340(23): 1796-9.