How does BabyMed rate the probability, such as the probability of ovulation, in the BBT curve?

The BabyMed experts evaluate your BBT curve visually and list probabilities in two areas (likelihood and day) and 3 categories (high, medium, low):
The first area of probability relates to how confident we are that ovulation actually took place. It answers your question: "Did I or did I not ovulate?"
The second area of probability relates to the day of ovulation. It answers your question: "What is the likelihood that the day we determine to be the ovulation day is actually the right day? and "Did I ovulate on that specific day?"

For each of these 2 areas we have the choice of 3 categories of probability, high, medium, and low:

High probability

Medium probability

Low probability

Nearly 100% Likelihood About 50%  Less than 25%


One good example would be a a slow-rising curve. We would tell you from the pattern that there is a 'high probability' of ovulation but only a 'medium probability' of the ovulation day. That means we are pretty confident you ovulated but we cannot tell you with enough certainty which day it happened. Another example would be a curve with discrepant findings of the first positive OPK or cervical mucus changes and the temperature rise. In that case we would more likely go by the changes in temperature if they are typical. If there is a high probability of the ovulation day then the probability that you ovulated is also high. The probabilities are usually determined as low (<25% probability), medium (about 50%), and high probability (about 100%). Assessing probability and deciding on the day of ovulation takes into consideration many factors including:

  1. The absolute rise in temperature (should be at least 0.2 or more degrees Fahrenheit).
  2. The elevated temperatures after the initial rise, that is, whether they stay elevated and for how many days they are elevated. We prefer a minimum of three days of elevated temperatures.
  3. The overall pattern of the chart (is it typically biphasic or not?).
  4. Is there a significant drop after the initial temperature rise?
  5. Factors such as the first positive OPK, fertility monitor changes, and cervical mucus changes.
  6. The cycle day of the presumed ovulation (that is, a rise in temperature before CD 7 and well after CD 21 is less likely to be ovulation)
  7. IMPORTANT: A completed cycle provides the best method to assess ovulation (please indicate at cycle end an "M" on the bleeding row to indicate that the cycle is completed).
  8. The general pattern of the BBT curve (yes, there is something like a 'too perfect' BBT chart)
  • High probability = Nearly 100% chance of the event happening
  • Medium probability = About 50% chance of the event happening
  • Low probability = Less than 25% chance of the event happening

Low probability usually means that BabyMed cannot determine exactly whether ovulation took place or when it happened. In general, we rate the ovulation probability no better than a "medium" unless it's fairly clear when and if ovulation has happened. Completed menstrual cycles have the best chance of getting a "high" rating. You can read MORE HERE about the probabilities of pregnancy with various symptoms.