What is HCG ?

The HCG ( Human Chorionic Gonadotropin ) test is done to check for HCG in blood or urine. HCG is a very interesting molecule. It is unusual because it is produced only by the trophoblastic cells of the embryo ( these cells are the ones which nourish the embryo and later develop into the placenta. )

It is detectable in the blood and urine within 10 days of fertilization and hence forms the basis of all pregnancy tests. Because HCG is produced by the placenta, the presence of HCG in a woman’s blood indicates that she is most probably pregnant. A pregnancy blood test or a pregnancy serum test measures the exact amount of the pregnancy hormone, HCG in the bloodstream.

An egg is normally fertilized by a sperm cell in a fallopian tube. Within nine days after fertilization , the fertilized egg moves down the fallopian tube into the uterus and attaches (implants) to the uterine wall. Once the fertilized egg implants, the developing placenta begins releasing HCG into your blood. Some HCG also gets passed in your urine. HCG can be found in the blood before the first missed menstrual period, as early as six days after implantation.

HCG helps to maintain your pregnancy and affects the development of your baby (fetus). Levels of HCG increase steadily in the first 14 to 16 weeks following your last menstrual period (LMP), peak around the 14th week following your LMP, and then decrease gradually. The amount that HCG increases early in pregnancy can give information about your pregnancy and the health of your baby. Shortly after delivery, HCG can no longer be found in your blood.

More HCG is released in a multiple pregnancy, such as twins or triplets, than in a single pregnancy. Less HCG is released if the fertilized egg implants in a place other than the uterus, such as in a fallopian tube. This is called an Ectopic pregnancy.

Ectopic Pregnancy

An ectopic pregnancy is an abnormal pregnancy that occurs outside the womb (uterus). The baby (fetus) cannot survive, and often does not develop at all in this type of pregnancy.

The vast majority of ectopic pregnancies are so-called tubal pregnancies and occur in the Fallopian tube (98%); however, they can occur in other locations, such as the ovary, cervix, and abdominal cavity. An ectopic pregnancy occurs in about one in 100 pregnancies.

In a typical ectopic pregnancy, the embryo adheres to the lining of the fallopian tube and burrows into the tubal lining. Most commonly this invades vessels and will cause bleeding. This intratubal bleeding may expel the pregnancy out of the tubal end as a tubal abortion. Some women who think they are having a miscarriage are actually having a tubal abortion. The pain is caused by prostaglandins released at the implantation site, and by free blood in the peritoneal cavity, which is a local irritant. Sometimes the bleeding might be heavy enough to threaten the health or life of the woman. A delay in diagnosis can be life-threatening.

If left untreated, about half of ectopic pregnancies will resolve without treatment. These are the tubal abortions. The advent of methotrexate treatment for ectopic pregnancy has reduced the need for surgery; however, surgical intervention is still required in cases where the Fallopian tube has ruptured or is in danger of doing so. This intervention may be laparoscopic or through a larger incision, known as a laparotomy.

Diagnosis of ectopic pregnancy

An ectopic pregnancy should be considered in any woman with abdominal pain or vaginal bleeding who has a positive pregnancy test. An ultrasound showing a gestational sac with fetal heart in the fallopian tube is clear evidence of ectopic pregnancy.

An abnormal rise in blood β-human chorionic gonadotropin (β-hCG) levels may indicate an ectopic pregnancy. The threshold of discrimination of intrauterine pregnancy is around 1000 IU/ml of β-hCG. A high resolution, transvaginal ultrasound showing no intrauterine sac is presumptive evidence that an ectopic pregnancy is present if the β-hCG level is more than 1000 mIU/ml.

What you need to know about DPO ( Days Post Ovulation )

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 a pregnancy as well, and should be something which 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 the 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 the ovulation in the present cycle, can vary considerably from woman to woman, and from cycle to cycle.

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

Why are blood tests for HCG better ?

Blood tests for checking the beta HCG level are better than home urine pregnancy tests for the following reasons.

  1. They are more accurate and reliable. A negative test ( HCG level of less than 10 mIU/ml) can reliably rule out a pregnancy with 100% accuracy. Urine tests are not as reliable or accurate. This is because they can have false negatives. A false negative is the situation when a woman is pregnant, but the urine pregnancy test comes back as negative. This can be because her HCG levels are low, so that they cannot be picked up by the urine test ( which becomes positive only after the blood HCG levels cross more than about 30-50 mIU/ml). Other reasons the urine test can be incorrectly negative is when it’s not done properly by the patient ( who is not an expert, after all, and can make errors !); and if the urine is too dilute ( so that the concentration of the HCG in the urine is too low for it to be picked up by the urine test). This is why an IVF clinic will never rely on a urine pregnancy test and will insist that the patient do a blood test to check their HCG level.
  2. They are quantitative. The other major advantage of a blood test over a urine test is that a urine test is only qualitative – it just gives a yes or no ( positive or negative) result. The blood test, on the other hand, provides a number. This is especially useful when the doctor needs to do serial tests to monitor the health of the pregnancy. Thus, in a healthy pregnancy, the HCG level should double every 48 hours. If it fails to do so, this gives the doctor an idea that there maybe a problem with the pregnancy. Similarly, a very high level can help the doctor to suspect a multiple pregnancy !

How is HCG Expert helpful for patient and doctor ?

  • HCG Expert will allow the early diagnosis of ectopic pregnancy, so this preventable complication does not occur.

  • HCG Expert will encourage patients to share information about their medical outcomes; and we can collate and analyse this data to improve the medical knowledgebase about the correlation of HCG levels and the pregnancy outcome

  • We hope this will serve as a proof of concept which specialists in other medical fields can build upon, to help promote patient-generated evidence based medicine.

  • Empowering patients with information therapy, so they can make sense of their own blood test results , rather than have to depend upon a doctor.

  • Demystify medicine and allow patients more control over the medical care their receive during their pregnancy.

  • The more the information you provide , the better will be the quality of HCG Expert’s data analysis in the long term – and the more useful this will be for other patients like you !