Pregnancy involves many bodily changes, and noticing an unusual vaginal odor, such as one that smells like onions, can be concerning. This change is common and is frequently linked to hormonal shifts and a heightened sense of smell. Normal pregnancy discharge, known as leukorrhea, is typically thin, milky, and has a mild scent. Hormones like estrogen and progesterone increase the volume of this discharge and alter the body’s chemistry. Many pregnant individuals also experience hyperosmia, an increased sensitivity to odors, making subtle smells seem much stronger and sometimes interpreting them as an onion or garlic scent.
Benign Causes of Pungent Odor
The most frequent reasons for an onion-like odor are not related to infection but result from normal pregnancy physiology. Hormonal fluctuations increase blood flow to the pelvic area, activating apocrine sweat glands in the groin. Skin bacteria break down this sweat, generating sulfurous compounds often perceived as a strong, pungent, or onion-like smell.
Dietary choices also play a direct role in how bodily secretions smell. Consuming strong-smelling foods, particularly garlic, onions (allium family), or high-sulfur vegetables like asparagus, influences the scent of sweat and urine. Since sweat and trace amounts of urine mix with discharge, these food compounds contribute to a temporary onion-like aroma.
Pregnancy hormones can cause the vaginal environment to become slightly more acidic, a natural defense mechanism against certain infections. This shift in vaginal pH balance subtly changes the scent of normal discharge. This change may be perceived as unusual or strong by the pregnant person’s sensitive nose. Practicing simple hygiene, such as wearing breathable cotton underwear, helps manage increased moisture and sweat.
Infectious Causes Requiring Treatment
While most odor changes are benign, a persistent or foul smell can signal an underlying infection requiring medical attention. The most common cause of abnormal vaginal odor is Bacterial Vaginosis (BV), resulting from an imbalance in the natural vaginal flora. BV is usually characterized by a strong, distinct fishy odor, which might be mistaken for a general foul smell, particularly after intercourse.
If BV is present, the discharge is typically thin and greyish-white, often accompanied by mild irritation, burning, or itching. Another infection to consider is Trichomoniasis, an STI that causes a strong, unpleasant odor. This infection is usually accompanied by a frothy, yellow or greenish discharge, along with pain during urination or intercourse.
Yeast infections (Candidiasis) are also more common in pregnancy due to hormonal shifts, but they generally cause a thick, white, cottage cheese-like discharge. The smell associated with yeast is often described as yeasty or bread-like. If an infection is the cause, the odor is typically accompanied by noticeable changes in the discharge’s color or consistency and significant discomfort.
When to Contact a Healthcare Provider
A change in odor alone is often harmless, but accompanying symptoms require contacting a healthcare provider for diagnosis and treatment. Seek medical advice if the onion-like odor is intense, persistent, and combined with a noticeable change in discharge color, such as green, yellow, or grey. These changes strongly suggest a bacterial or parasitic infection, like BV or Trichomoniasis, which requires prescription medication during pregnancy.
Red Flags
Other red flags warranting immediate attention include intense vulvar or vaginal itching, burning, or swelling. Contact your provider immediately if the odor is accompanied by a fever, chills, severe pelvic pain, or unusual bleeding or spotting. Self-treating a suspected infection is not recommended, as only a medical professional can perform the necessary tests to correctly identify the cause and ensure a safe treatment plan.