Bacterial Vaginosis (BV) is a common condition caused by an imbalance in the vaginal microbiome, where protective bacteria are replaced by an overgrowth of other mixed bacteria. While BV is an infection of the lower reproductive tract and does not directly cause infertility, the inflammatory environment it creates can lead to serious complications. Damage occurs when the infection progresses upward from the vagina to the uterus and fallopian tubes. Understanding this progression is important for minimizing reproductive risk.
Understanding Bacterial Vaginosis
Bacterial Vaginosis occurs when the dominant Lactobacilli bacteria in the vagina are significantly reduced, allowing an overgrowth of anaerobic bacteria. This microbial shift is not considered a sexually transmitted infection, though sexual activity can increase the risk of developing it. Common signs of this imbalance include a thin, grayish-white vaginal discharge and a distinct “fishy” odor, often more noticeable after sexual intercourse.
Many people with BV experience no symptoms. Diagnosis is made through a clinical examination and laboratory tests of vaginal fluid. BV is usually treated with antibiotics, such as metronidazole or clindamycin, administered orally or as a vaginal gel or cream. Prompt treatment restores the normal vaginal flora and prevents more serious health issues.
The Pathway from Untreated BV to Pelvic Inflammatory Disease
If the microbial shift defining BV is left unaddressed, it creates a less acidic environment hospitable to harmful microorganisms. This compromised state allows bacteria to ascend from the vagina and cervix into the upper reproductive tract. Normally, the cervix acts as a barrier, preventing this upward migration.
Pelvic Inflammatory Disease (PID) is an infection of the female reproductive organs, including the uterus, fallopian tubes, and ovaries. BV-associated bacteria, such as Gardnerella vaginalis and Mycoplasma hominis, have been recovered from the reproductive organs of women with PID, establishing a clear link. BV also increases susceptibility to other infections, including sexually transmitted infections, which are the most common cause of PID. PID, caused by ascending bacteria, is the direct precursor to infertility.
How Pelvic Inflammatory Disease Causes Infertility
PID damages fertility by inducing inflammation and structural changes within the fallopian tubes. The inner lining of the tubes contains cilia, which move the egg from the ovary toward the uterus. During PID, infection and inflammation destroy these ciliated cells, impairing the tube’s ability to transport the egg.
As the inflamed tissue heals, scar tissue or adhesions often form inside and outside the fallopian tubes. This scarring can partially or completely block the tubes, causing tubal factor infertility. Blocked tubes prevent sperm from reaching the egg or prevent the fertilized egg from traveling to the uterus. This permanent damage accounts for a significant portion of female infertility cases. Partial damage also increases the risk of an ectopic pregnancy, a life-threatening complication where a fertilized egg implants outside the uterus.
Timeline and Risk Factors for Complications
There is no fixed time frame after which untreated BV inevitably leads to infertility. The progression from BV to PID and reproductive damage is variable and depends on individual factors. Progression is often subclinical, meaning a person may not experience noticeable PID symptoms while damage occurs. The risk of complications, including infertility, accumulates with the duration and number of untreated episodes of upper tract infection.
Factors that increase the likelihood of progression include recurrent BV, co-existing sexually transmitted infections, and a history of previous PID. Women with a high density of BV-associated bacteria have an increased risk of developing PID. While a single, promptly treated BV episode carries a low risk, the cumulative effect of repeated or prolonged untreated infections significantly elevates the chance of long-term reproductive complications.