What you need to know about DPO

We all know that ovulation is the central event in a woman's reproductive cycle. All reproductive events ( for example, timing baby-making sex) depend upon this. It's the key event to dating pregnancy as well and should be something that every woman should know about her body.

Unfortunately, because ovulation is a silent internal event, most women are not sure when this occurs. They do not track their cervical mucus or ovulation, and lose valuable information their body provides to them free of cost every month! Doctors are also to blame, as we usually don't take the time and trouble to teach women about the significance of their DPO.

This is why most women still use their last menstrual period ( LMP ) as their key reference timing milestone. This creates a lot of confusion.

DPO stands for Day Post Ovulation and is a key term every woman needs to be aware of.

It's only women who have a textbook 28-day menstrual cycle in which ovulation occurs on Day 14. In reality, life is far more unpredictable. This is why women often have to use additional tools such as ovulation prediction kits, BBT charts, and ultrasound scans, to pinpoint the day of ovulation.

The reason for this confusion is that while the luteal phase which is the period between ovulation and the next menstrual period is fairly constant at about 14 days, the length of the follicular phase-which is the time period between the last menstrual period and ovulation in the present cycle, can vary considerably from woman to woman, and from cycle to cycle.

This is why the free fertility calculator at www.myfertiletime.in can be such a useful tool.

Knowing how to calculate your DPO ( which means you need to able to pinpoint when you ovulate ) is critically important when :
1. you are timing baby-making sex
2. in order to date your pregnancy. This is important data, especially when you're trying to find out whether your pregnancy is healthy or not; and when interpreting your hCG levels and ultrasound scan findings

Because most women do not know what their data of ovulation is, most doctors ( and pathology reports) still use the last menstrual period when talking about pregnancy and hCG levels. Thus, when your doctor says you are five weeks pregnant, he's referring to the clinical age of your pregnancy - which is the menstrual age as measured from the date of your last menstrual period, and not the real biological age of your embryo. This creates a lot of confusion. This confusion is compounded even further when trying to make sense of hCG levels. Normal ranges for hCG levels are usually printed in the form of clinical weeks of pregnancy, and most reports refer to completed weeks after the last menstrual period.

This is especially true in the case of IVF pregnancies! Many women who get pregnant after IVF get hopelessly confused when trying to date their pregnancies - and this is completely understandable because it is doctors who confuse the issue and use a shortcut, only because this has been the clinical convention for many years! Let's look at a woman whose last menstrual period was 1 Jan; whose egg collection was 14 Jan; and whose D3 embryo transfer was on 17 Jan. She does her HCG blood test on 31 Jan and gets a positive result of 200 mIU/ml. Her doctor tells her that she is now four weeks pregnant because clinically we use menstrual age when talking about pregnancy. However, she finds this very confusing because she knows that she can only have got pregnant after the doctor actually transferred the embryos into her uterus!

So why don't we calculate an IVF pregnancy in terms of the date of embryo transfer? Why do we still prefer using DPO, even in IVF pregnancies? This is because some clinics transfer embryos back on day two, while others do so on day five, which is why the date of egg collection (DPO) is far more constant and reliable.

While none of this makes much difference in a healthy uneventful pregnancy it can be extremely important when you have a nonviable pregnancy or an ectopic pregnancy, for example. This is why you must understand the difference between DPO and LMP

Authored by : Dr Aniruddha Malpani, MD and reviewed by Dr Anjali Malpani.

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