You don’t need to have progressed very far into your gestation before hCG starts to play a pretty important role in the way your body is starting to nurture your baby. Human chorionic gonadotropin is manufactured by the cells that will eventually become the placenta as it forms in the very early stages of pregnancy.
hCG stimulates the corpus luteum, which is the portion of the ovarian follicle where the egg was released. Think about an empty egg cup and you’ve got a pretty accurate idea. The corpus luteum needs to produce oestrogen and progesterone in the first 10 weeks or so after conception, until the placenta starts to do this by itself. These hormones help to build up the lining of your womb, filling it with blood, so that it can sustain the growing embryo.
This whole process is like the ultimate feedback loop; as one collection of tissues and cells finish their unique jobs another one takes over. All of this is being done without you having any idea that it is happening – you have no conscious control over it.
Within around 2 weeks of the newly conceived embryo implanting itself in the walls of the womb, hCG can be detected in your urine. It can be detected in your blood a little earlier, at around 11 days after conception.
How will I know if I’m producing hCG?It is because of hCG that early pregnancy symptoms make themselves known. Nausea, feeling “off”, being sensitive to smells and tastes, fatigue, breast tenderness – we have hCG to thank for most of them. Science has proven that it is not just the presence of hCG, but also the levels of hCG circulating in a mother’s body, that influences her pregnancy symptoms. If the level is high then you are likely to feel “more” pregnant.
This is why it’s not uncommon for healthcare professionals to reassure mothers who feel particularly nauseous in the early days of their pregnancy that this can be a sign of a more stable pregnancy. But extreme nausea can also be a sign of multiple pregnancy - because so much hCG is being produced.
The role of hCG is unique to pregnancy – without it the embryo cannot survive, nor can your pregnancy progress as it needs to. The level of hCG climbs rapidly in the early weeks of pregnancy and peaks between weeks 8 to 11. In fact, it generally doubles every 2 to 3 days in the first few weeks. Although it is very low in the early stages of pregnancy, within days it quickly multiplies.
What’s important to know about hCG levels?
- The levels of hCG vary between individual women and cannot be compared.
- There is a wide variation between normal levels.
- hCG levels also vary from day to day. The concentration of hCG is dynamic and not stable. This is why comparisons are rarely useful.
- A woman cannot do anything specific to influence her hCG levels. Some medications that are used in fertility treatments will influence hCG levels, but this is usually accounted for when looking at hCG test results.
- The highest biological source of hCG is in a pregnant mother’s urine. Sometimes this becomes the scientific source of collection and then used for other mothers who are undertaking fertility treatment.
- There is not necessarily a correlation between a mother’s hCG level and how a woman feels. There are many factors that can account for pregnancy symptoms, and hCG level is just one of them.
- Home pregnancy tests work by detecting hCG in the mother’s urine. They do not give a specific reading of the hCG level detected.
- Because urine tests work by detecting the presence of hCG, it is not possible to have a false positive reading for pregnancy. If the hCG is present in a sufficiently high concentration then the reading will be positive. However, it is possible to have a false negative reading, particularly if it is very early into the pregnancy and not enough hCG can be detected in the urine.
- There is no “normal” hCG level in early pregnancy. There is such a wide variation between individual women that pinpointing specific numbers is impossible.
Specific measurements of hCG levels are not routinely done, unless the doctor or healthcare professional has specific concerns regarding the viability of the pregnancy. In cases where there has been an incomplete miscarriage, vaginal bleeding and/or uterine cramping, a blood level check of hCG can be done to confirm whether the pregnancy is still viable. Even then, an ultrasound is done to gather more supportive evidence.
What does a low hCG level mean?It could mean that it is too early in the pregnancy for the level to have risen as much as it is going to. There may be some confusion about how far advanced the pregnancy is. The pregnancy may not be viable and could possibly be a blighted ovum (an empty pregnancy sac), or there may be an ectopic pregnancy (in the fallopian tube).
Any interruption to the embryo embedding in the lining of the womb and the production of hCG will be reflected in the hCG levels. But the majority of pregnant women will never know what their individual levels of hCG are, unless they are undertaking fertility treatment.
If a woman has had a miscarriage, ectopic pregnancy or termination of pregnancy, then her levels of hCG will most likely return to normal levels within 4-6 weeks after the pregnancy ended. In women whose levels are particularly high, it may take longer for her levels to stabilise.
For women who have had a dilatation and curette (D & C) after an incomplete miscarriage or a termination of pregnancy, their pregnancy symptoms can take a while to settle. Although consciously they know they are no longer pregnant, their hormones may be telling them another thing entirely.
What does a high hCG level mean?- There may be a multiple pregnancy or a pregnancy where there has been an interruption to the normal growth of the embryo; specifically a molar pregnancy.
- High levels can also be detected when a woman is further advanced in her pregnancy than she originally thought she was.
- Some cancerous tumours can produce hCG, which is why investigations are necessary if there is any doubt about a woman’s pregnancy or suspicions that all is not well.
There are some alternative healthcare practitioners who claim that taking hCG helps to influence weight loss. This is a risky business and there is no science or evidence to support these claims. If something sounds too good to be true, then it generally is. The hormone hCG is a pregnancy-specific hormone and taking it artificially is potentially very risky and best avoided.
