Hormonal shifts increase blood flow and vaginal secretions.

Many pregnant women notice temporary changes in vaginal odor that are not caused by infection.

Reason #4: An Infection or Imbalance

Although a mild sour smell is often normal, a sudden or persistent change in odor—especially when accompanied by other symptoms—may indicate an infection or imbalance.

Several conditions can affect the vaginal microbiome.

Bacterial Vaginosis (BV)

BV is one of the most common vaginal conditions.

It occurs when harmful bacteria outnumber the normal Lactobacillus bacteria.

Common symptoms include:

• Thin gray or white discharge

• A strong fishy odor, especially after sex

• Mild irritation

• Increased discharge

Interestingly, BV is more commonly associated with a fishy odor than a sour odor.

Yeast Infection

A yeast infection is caused by an overgrowth of Candida.

Symptoms often include:

• Thick white discharge that resembles cottage cheese

• Intense itching

• Redness

• Burning

• Soreness

Some women notice a mildly sour or bread-like smell, although many experience little or no odor at all.

Trichomoniasis

This sexually transmitted infection may cause:

• Yellow-green discharge

• Frothy discharge

• Strong unpleasant odor

• Pain during urination

• Vaginal irritation

Prompt medical treatment is recommended.

Retained Foreign Object

Occasionally, a forgotten tampon or menstrual product may cause:

• A very strong foul odor

• Abnormal discharge

• Pelvic discomfort