When a pregnant woman’s water breaks, also known as rupture of membranes (ROM), it signals that labor is likely to begin soon. The amniotic sac, filled with amniotic fluid that surrounds and cushions the baby in the womb, ruptures and leaks fluid through the vagina. This fluid has a distinct smell that can vary from woman to woman.
What Causes the Smell?
The source of the smell when your water breaks is the amniotic fluid. This fluid is comprised mainly of water along with electrolytes, carbohydrates, proteins, lipids, and fetal cells and waste. The composition of amniotic fluid changes as pregnancy progresses, which affects the odor.
In early pregnancy, amniotic fluid is made up largely of water and electrolytes. As the baby grows, it begins to produce urine which enters the amniotic fluid. Vernix caseosa, the waxy white substance coating the baby’s skin, and lanugo, the fine hair on the skin, can also mix with the fluid. Later in pregnancy, the baby’s lungs begin to produce surfactant, a substance that allows the air sacs to inflate properly. Mucus from the baby’s gastrointestinal and respiratory tracts also mixes with the amniotic fluid.
The combination of these substances contributes to the smell released when the sac ruptures close to labor. The odor is often described as sweet or bleach-like early in pregnancy due to the watery composition. As more substances accumulate, the smell becomes more pungent and distinctive.
What Does it Smell Like?
Here are some of the common descriptions of how amniotic fluid smells when your water breaks:
- Sweet or saccharine
- Bleachy or chlorine-like
- Musky or earthy
- Metallic or coppery
- Fishy or seafood-like
- Alkalic or ammonia-like
The smell can vary from woman to woman and even from pregnancy to pregnancy. The individual smells depend on the particular combination of substances present in your amniotic fluid at the time your membranes rupture.
Sweet or Saccharine Smell
Many women report their amniotic fluid smells sweet, similar to honey or sugar water. This is likely due to the high water and carbohydrate content early in pregnancy before other substances accumulate.
Bleach-like Smell
Some women describe the smell as chlorine-like or similar to bleach. This clean, sharp scent may come from disinfectants and antimicrobial proteins present in amniotic fluid.
Musky or Earthy Smell
As the baby excretes waste into the amniotic fluid, some women notice an earthier, musky odor. This likely comes from the urine mixing with other substances.
Metallic or Coppery Smell
Iron and other minerals contribute to a metallic or coppery scent you may notice when your water breaks. Blood from vaginal exams during pregnancy can also mix with the amniotic fluid and create this smell.
Fishy Smell
The smell is sometimes described as fishy or seafood-like. This may come from protein breakdown products and fatty acids present in vernix, lanugo, and sebum mixing with the amniotic fluid.
Alkaline or Ammonia Smell
An alkalic, urine-like scent can occur when the baby’s urine mixes with the amniotic fluid. The urea in urine breaks down into ammonia which has a pungent odor.
What Affects the Smell?
Several factors can influence the specific scent when your water breaks:
- Gestational age – Smell changes with increasing gestational age as more substances accumulate.
- Baby’s sex – Some research suggests amniotic fluid may smell different with male vs. female babies.
- Maternal diet – What you eat can affect the smell due to substances transferred into the amniotic fluid.
- Infection – Bacteria introduced through vaginal exams or infections like chorioamnionitis can create foul odors.
- Smoking – Tobacco byproducts are excreted into the fluid and can influence smell.
- Genetics – Genetic variations in metabolic pathways may lead to distinct scents.
Therefore, each woman’s experience can be unique. If you notice a very strong or foul odor, it is a good idea to call your healthcare provider to rule out infection.
When Does the Smell Occur?
You are most likely to notice a smell when your water breaks as you near labor at term. However, the smell may also be present with leakage or rupture earlier in pregnancy:
- First trimester: Odor is usually faint and sweet.
- Second trimester: Smell becomes stronger as more substances accumulate.
- Third trimester: Odor is most pungent around full term.
Talk to your doctor promptly about any amniotic fluid leakage you experience before 37 weeks, as this may signal a complication like preterm premature rupture of membranes (PPROM).
Does the Smell Indicate a Problem?
Most of the time, the smell of amniotic fluid when your water breaks is normal and not indicative of issues. However, in some cases, it can signal problems:
- Foul odor – A truly foul, rotten smell may indicate infection like chorioamnionitis.
- Sweet odor with leakage – A sweet smell earlier than 37 weeks with leaking fluid can occur with PPROM.
- No odor – Lack of any smell with suspected leakage should also be evaluated.
Discuss any concerns about the odor, especially if it seems particularly strong or abnormal. Your healthcare provider can check for signs of infection and examine you for any complications.
Tips for Minimizing Odor
To help minimize odor after your water breaks:
- Wear a sanitary pad – This contains fluid rather than letting it drain freely.
- Change pads frequently – Changing pads often prevents saturation.
- Use odor absorbers – Pads with baking soda or charcoal can help trap smells.
- Wash area routinely – Gently cleanse the vaginal area when changing pads.
- Avoid douching – This can introduce new bacteria and make odors worse.
The smell should dissipate after delivery as the source of the amniotic fluid is no longer present. See your provider if odor persists postpartum as this can signal retained tissue or infection.
When to Call the Doctor
Contact your healthcare provider if you experience:
- Gush or steady leaking of fluid before 37 weeks
- Foul-smelling fluid leakage
- Odor accompanied by symptoms like fever, abdominal pain, uterine tenderness
- Fluid tinged with blood or meconium
- No perceptible odor with suspected amniotic fluid leakage
Calling promptly when you notice signs of ROM will allow your provider to assess the situation and monitor you for potential complications.
Conclusion
When your water breaks, you may notice a distinctive odor ranging from sweet to pungent. The smell comes from the combination of substances present in amniotic fluid like water, proteins, lipids, carbohydrates, and fetal urine and waste. The specific scent can vary based on gestational age, baby’s sex, maternal diet, infections, genetics, and other factors. While most odors are normal, a truly foul smell could indicate infection. Noticing what your amniotic fluid smells like when your membranes rupture can provide insight into your health and pregnancy status as you near labor.