Biochemical pregnancies can occur in natural conception, intrauterine insemination (IUI), or in vitro fertilization (IVF). Even women who have no difficulties conceiving may experience biochemical pregnancies several times in their lifetime. In natural pregnancies, biochemical pregnancies are sometimes detected due to early testing; other times, they go unnoticed because menstruation occurs, and the biochemical pregnancy resolves without leaving any signs.
In contrast, with IUI or IVF, biochemical pregnancies are almost always detected because blood tests are routinely performed after treatment to confirm the outcome.
A biochemical pregnancy refers to an embryo that has implanted and begun secreting HCG into the mother’s bloodstream at a detectable level (in urine or blood). However, for some reason, the embryo does not continue to grow and instead withers away, causing HCG levels to drop. Since this type of pregnancy only progresses to a stage detectable through biochemical methods (and not yet visible as a gestational sac via ultrasound), it is termed “biochemical pregnancy.”
If the pregnancy progresses to a stage where a gestational sac is visible in the uterine cavity via ultrasound, it is considered a clinical pregnancy. If pregnancy loss occurs after clinical pregnancy but before 28 weeks (or 20 weeks in some countries), it is termed a miscarriage.
Both biochemical pregnancy and miscarriage are forms of pregnancy loss. However, under strict diagnostic criteria, biochemical pregnancy is not yet considered part of miscarriage history. Recurrent biochemical pregnancies, however, are clinically significant and indicate an underlying cause that needs to be investigated.
Causes of Biochemical Pregnancy:
- Embryo Defects
Genetic factors, such as chromosomal abnormalities in number or structure, can lead to poor embryonic development. Chromosomal abnormalities are considered the primary cause of biochemical pregnancy and account for over 50% of early spontaneous miscarriages within the first three months of pregnancy. - Luteal Phase Deficiency
Insufficient progesterone production from the corpus luteum can lead to abnormal endometrium and implantation failure. However, this is rarely a concern for women undergoing IVF, as doctors provide sufficient luteal support during the process. - Uterine Factors
Issues such as uterine malformations, thin endometrium, endometrial polyps, intrauterine adhesions, submucosal fibroids, or endometrial tuberculosis can interfere with embryo implantation. - Lifestyle Factors
Smoking (including secondhand smoke), alcohol consumption, exposure to chemical toxins, severe noise or vibration, emotional disturbances (anger, extreme joy or sadness, shock), and high-temperature environments can damage the placenta and embryo, leading to biochemical pregnancy or miscarriage. - Infections
Bacterial or viral infections during or around pregnancy can damage the ovum, fertilized egg, or embryo, affecting development and resulting in biochemical pregnancy or miscarriage. - Nutritional Deficiencies
Poor nutritional support at the implantation site may prevent the embryo from sustaining its development, especially if implantation occurs in a less-than-ideal location such as the fallopian tubes or other areas outside the uterine cavity. - Maternal Metabolic or Immune Abnormalities
Conditions like polycystic ovary syndrome (PCOS) with uncorrected glucose and lipid metabolism disorders, or immunological issues such as alloimmune or autoimmune abnormalities, can lead to biochemical pregnancy.
Understanding Biochemical Pregnancy:
Biochemical pregnancy is often considered a form of natural selection. Most cases result from poor embryo quality or random factors causing chromosomal abnormalities, leading to natural rejection. According to Darwin’s theory of evolution, survival of the fittest is nature’s way of ensuring species advancement through genetic variation and natural selection. Human embryos follow the same rule, with approximately 70% naturally eliminated—some even before reaching implantation.
In natural conception, about 30% of pregnancies end as biochemical pregnancies, excluding clinical pregnancy losses. In IVF, the rate is about 5%, also excluding clinical pregnancy losses.
Thus, an occasional biochemical pregnancy can be viewed as nature’s selection process. The embryo that didn’t stay might simply not have been the right one. Letting go without regret can provide peace of mind.
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