Table of contents:

1. Chorionic gonadotropin
2. Examples of standards
3. More important than the absolute values of HCG are the increases in its concentration over time!
4. HCG and Medical US

Infertility is not only the absence of pregnancy but also the inability to carry a pregnancy to term and the occurrence of ectopic pregnancies. Therefore, in some cases, careful monitoring of the early stages of pregnancy is important. The author hopes that the article will also serve all those for whom the road through infertility has ended, but who are still anxious about the state of their long-awaited, effortlessly achieved pregnancy and are looking for confirmation that it is developing correctly.

Chorionic gonadotropin

Is a hormone produced by the chorionic villi of the placenta. It consists of two subunits alpha and beta. The alpha subunit is common to HCG, TSH and LH, the beta subunit is specific to HCG. Chorionic gonadotropin maintains the function of the corpus luteum in early pregnancy (up to 8-10 weeks). If implantation of the fertilised ovum occurs, and this takes place between 6 and 8 days after ovulation, a detectable concentration of HCG (> 1 mIU/ml) appears in the blood 48 hours later. But since many embryos are genetically defective (some believe up to 50 % of them) and "micro-abortions" often occur, only a result > 5 mIU/ml (for some > 25 mIU/ml) indicates pregnancy. HCG is also detectable in urine and this property is used by home pregnancy tests.

The level of HCG reaches its peak at 8-10 weeks of pregnancy, then its level decreases and remains so for the rest of the pregnancy.

In women who have received HCG-containing preparations in the cycle preceding pregnancy, detectable concentrations of the hormone persist for 5 to 14 days depending on the dose used and the individual response of the body (the average is 10 days).

The norms for HCG values depending on the gestational age calculated from the first day of the last menstrual period are very wide.

Examples of norms

Weeks of pregnancy	beta hcg level
3	5-50 mIU/ml
4	5-430 mIU/ml
5	19-7340 mIU/ml
6	1000-56000 mIU/ml

More precise normal ranges can be obtained if the date of ovulation is known.

Examples of HCG concentration values:

• 3rd week - 5 - 50
• 4 week - 3 - 426
• 5 week - 19 - 7,340
• week 6 - 1,080 - 56,500
• 7-8th week - 7,650 - 229,000
• 9-12 week - 25,700 - 288,000
• 13-16th week - 13,300 - 254,000
• 17-24th week - 4,060 - 165,400
• 25-40th week - 3,640 - 117,000

More important than the absolute values of HCG are the increases in its concentration over time!

In a normal pregnancy the HCG level rises by at least 66% in 48 hours and by 114% in 72 hours. The older the pregnancy the slower the rise in HCG concentration and in the range 1200 mIU/ml-6000 mIU/ml HCG levels double in an average of 96 hours (4 days) and for concentrations above 6000 mIU/ml this time can be even longer. With HCG levels in excess of 6000 mIU/ml, better information on the status and location of the pregnancy is given by Medical US. Abnormal values raise the suspicion of miscarriage or ectopic pregnancy (the rise is slower than normal). However, a temporary drop in HCG concentration is possible if at least two embryos have implanted in the uterus (which happens with multiple ovulation or after IVF treatment) when one of them dies. The successful course of the pregnancy is not affected in this case.

The indication for HCG testing is also to monitor the effectiveness of treatment of ectopic pregnancies with methotrexate and the surveillance carried out after treatment of chorionic glands or chorionic tumours.

Comments:

1. In early pregnancy, the symptoms of ovarian hyperstimulation syndrome worsen suddenly due to increasing HCG levels.
2. Due to the corpus luteum-stimulating properties of HCG, drugs containing it are used to correct luteal phase disorders and to maintain pregnancy. It is an alternative to progesterone supplementation.
3. Because of HCG's similarity to LH, HCG-containing drugs are used as a substitute for LH to artificially induce follicular rupture.

HCG and Medical US

In a woman with 28-day menstrual cycles, a pregnancy follicle is earliest visible on Medical US vaginally on day 32 of the cycle, with HCG levels greater than 1000 mIU/ml (earliest at 500 mIU/ml)

The diameter of the follicle increases by an average of 1 mm per day (at least 0.6 mm). An echo of the embryo is most commonly seen in a follicle 10-25 mm in diameter.

Pathology may be indicated by:

• Absence of a gestational follicle with HCG >= 1500 mIU/ml (Note: In ectopic pregnancy there may be a so-called pseudo follicle).
• Absence of an embryo echo with a follicle over 25 mm in diameter.