What Causes a Chemical Pregnancy?

Biochemical pregnancy may occur with natural conception, intrauterine insemination (IUI), or assisted reproductive technologies such as in vitro fertilization (IVF). Even women without fertility difficulties may experience biochemical pregnancy several times throughout their lives. Recurrent biochemical pregnancies are clinically significant—there is always an underlying cause. Therefore, it is essential to investigate the potential causes of biochemical pregnancy.

What Causes Biochemical Pregnancy?

1. Genetic factors: Chromosomal numerical or structural abnormalities—often due to genetic causes—can impair embryonic development. Embryonic chromosomal abnormalities are widely considered the leading cause of biochemical pregnancy. In early pregnancy, chromosomal abnormalities account for over 50% of miscarriages.

2. Luteal phase insufficiency: Inadequate luteal function leads to insufficient progesterone secretion and abnormal endometrial development, thereby compromising embryo implantation in the uterus. For women undergoing IVF, this concern is largely mitigated, as they routinely receive adequate luteal-phase support medication.

3. Uterine factors: These include uterine hypoplasia, thin endometrium, endometrial polyps, endometrial tuberculosis, intrauterine adhesions (Asherman’s syndrome), and submucosal uterine fibroids—all of which can interfere with embryo implantation.

4. External factors: Smoking (including secondhand smoke), alcohol consumption, exposure to chemical toxins, intense noise or vibration, extreme emotional fluctuations (e.g., anger, excessive joy, grief, or severe anxiety), and high-temperature environments may damage the placenta and embryo, resulting in biochemical pregnancy or miscarriage.

5. Bacterial or viral infections: Infections with bacteria or viruses before or during early pregnancy can adversely affect oocytes, zygotes, and embryos, disrupting normal development and potentially causing biochemical pregnancy or miscarriage.

6. Nutritional deficiencies: Poor nutritional supply may compromise embryo implantation. While it remains too early to definitively determine whether implantation occurs ectopically (e.g., elsewhere in the fallopian tube) or within the uterine cavity, inadequate nutrient availability may contribute to biochemical pregnancy.

Occasional biochemical pregnancy, in a sense, represents a form of natural selection. As Darwin’s theory of evolution teaches us, “survival of the fittest” governs nature’s process of selection—favoring the strong and eliminating the weak. Human embryos likewise evolve continuously through genetic inheritance, variation, and natural selection. A biochemical pregnancy reflects nature’s selective process; there is no need for regret. However, if recurrent biochemical pregnancies occur—defined as three or more consecutive episodes—it is advisable to investigate the above-mentioned causes thoroughly to prevent unnecessary physical and emotional distress.