How does Natural Cycles determine how far into my pregnancy I am?
At Natural Cycles, we count that the pregnancy starts from the detected ovulation day - this is when conception happens and the egg is fertilized by the sperm.
Your pregnancy weeks are then calculated by adding 14 days to your ovulation day, which is confirmed by the algorithm based on the data you have entered.
The 14 days are added to align with how healthcare professionals calculate your due date. The healthcare system counts the pregnancy weeks starting on the first day of your last period, assuming that ovulation happens on CD14. However, many people do not ovulate on cycle day 14, since all cycles are different.
Later in pregnancy, how far along you are is determined by ultrasound - but again, this isn’t directly linked to ovulation day. This is why the due date you get from the midwife may differ from Natural Cycles’ due date.
In the ‘Calendar’ view, you will see the count of days/weeks since the start of the pregnancy day by day. However, in the ‘Pregnancy’ view, you will see the general overview of the week that you are currently in.
For that reason, the week number in the ‘Pregnancy’ view will always be higher than the week number in the ‘Calendar’ view.
To illustrate this: if you are on week 0+5 days, this would mean that you are in the first week of the development of the baby (week 1). If the conception date was four weeks ago, this would mean that you are entering the fifth week of pregnancy.