Leaking amniotic fluid means the protective sac surrounding your baby has developed a tear or rupture, allowing fluid to escape. This can happen as a normal part of labor starting (your “water breaking”) or, less commonly, earlier in pregnancy when it requires prompt medical attention. About 10% of pregnancies at full term experience this before labor begins, while 2 to 3% of pregnancies experience a preterm leak, which is the leading identifiable cause of preterm delivery in the United States.
How to Tell It’s Amniotic Fluid
The trickiest part of a suspected leak is figuring out whether the fluid is actually amniotic fluid, urine, or normal vaginal discharge. Late in pregnancy, all three can catch you off guard, and they feel surprisingly similar. Here’s how to tell them apart.
Amniotic fluid is mostly clear, sometimes with a pale straw-yellow tint, and it has no smell. That last detail is the most useful clue: urine almost always has a noticeable odor, and you can usually stop the flow by squeezing your pelvic floor muscles. Amniotic fluid, on the other hand, leaks on its own timeline. You can’t control it, and it may come as a sudden gush or a slow, persistent trickle that keeps wetting your underwear no matter what you do.
Normal vaginal discharge tends to be thicker, white or slightly cloudy, and doesn’t soak through a pad. If you’re unsure, put on a clean pad and check it after 30 minutes to an hour. A pad that’s wet with colorless, odorless fluid is more likely amniotic fluid than anything else. One important warning sign: fluid that looks green or brown may mean the baby has passed their first stool (meconium) into the fluid, and a foul smell can signal infection. Both need immediate medical evaluation.
What Your Provider Checks For
If you go in with a suspected leak, the evaluation is straightforward and usually quick. The two most common tests involve checking the fluid’s pH and looking at a dried sample under a microscope.
Your vaginal environment is naturally acidic, with a pH below 5.0. Amniotic fluid is more alkaline, with a pH above 6.0. A simple paper strip placed against the fluid changes color to confirm which one it is. This test catches true leaks about 90 to 97% of the time, though it can occasionally give a false positive from other alkaline fluids like blood or semen.
The second test involves letting a small sample of fluid dry on a glass slide. Amniotic fluid dries in a distinctive fern-like branching pattern that’s visible under a microscope. Your provider may also use ultrasound to measure the total volume of fluid remaining around the baby. Normal amniotic fluid levels fall between 5 and 25 centimeters on the amniotic fluid index. A measurement below 5 suggests the fluid is too low, a condition called oligohydramnios.
Why the Timing Matters
The significance of a leak depends almost entirely on how far along you are. Doctors draw a sharp line at 37 weeks of pregnancy.
A leak at or after 37 weeks (called term prelabor rupture of membranes, or term PROM) is common and usually means labor is close. Most people go into labor on their own within 24 hours. If contractions don’t start within that window, your provider will likely recommend inducing labor because the longer the sac stays open, the higher the risk of infection reaching the baby.
A leak before 37 weeks is called preterm PROM (PPROM), and it’s a more serious situation. It complicates roughly 150,000 pregnancies per year in the U.S. and is responsible for 30 to 40% of all preterm deliveries. The earlier it happens, the greater the concern, because the baby still needs time to develop, especially the lungs. A leak before the baby is considered viable (around 23 to 24 weeks) is particularly rare, occurring in less than 0.4% of pregnancies, and presents the most complex decisions about management.
Risks of a Prolonged Leak
Amniotic fluid does more than cushion your baby. It keeps the temperature stable inside the uterus, gives the baby room to move and develop muscles and bones, and protects against infection by acting as a barrier between the baby and the outside world. When that barrier is broken, several things can go wrong.
Infection is the primary concern. Once the sac is open, bacteria from the vagina can travel upward into the uterus. This type of infection, called chorioamnionitis, can cause fever, a rapid heartbeat, and tenderness in the uterus. It’s dangerous for both you and the baby, and it’s the main reason providers don’t wait indefinitely after membranes rupture.
Low fluid levels also increase the risk of umbilical cord compression. With less fluid cushioning the cord, it can get squeezed between the baby and the uterine wall, temporarily reducing the baby’s oxygen supply. In very early and prolonged leaks, persistently low fluid can restrict the baby’s movement enough to affect lung development or limb positioning.
What Happens After a Preterm Leak
If your membranes rupture before 37 weeks, the goal is to balance two competing priorities: giving your baby more time to mature while minimizing the risk of infection. What that looks like depends on gestational age.
Between 34 and 37 weeks, the decision about when to deliver has shifted in recent years. Current guidelines from the American College of Obstetricians and Gynecologists address the timing of delivery in this specific window, and many providers now recommend delivery relatively soon after confirming the leak rather than waiting weeks. The baby’s lungs are usually mature enough by this point that the risks of infection outweigh the benefits of staying pregnant.
Before 34 weeks, the calculus changes. You’ll typically be admitted to the hospital for close monitoring. The main interventions focus on speeding up fetal lung development and preventing infection. You can expect regular temperature checks, blood work, and fetal heart rate monitoring. The medical team watches closely for any signs that infection has set in or that the baby is in distress, either of which would trigger delivery regardless of gestational age.
Throughout this period, ultrasound is used to track how much fluid remains around the baby. Some small leaks reseal on their own, and fluid levels can stabilize or even return to normal. But a persistent, significant loss of fluid changes the outlook and may move up the delivery timeline.
Slow Leak vs. Full Rupture
Not every leak is a dramatic gush. A small tear high up in the amniotic sac can produce a slow, intermittent trickle that’s easy to dismiss as bladder leakage, which is extremely common in pregnancy. You might notice dampness that comes and goes, or a watery spot on your sheets when you wake up.
These slow leaks can be harder to diagnose because by the time you reach your provider’s office, the fluid may have stopped temporarily. If your initial tests come back negative but you continue to notice intermittent wetness that’s colorless and odorless, it’s worth going back for repeat testing. Small high leaks sometimes reseal on their own as the membranes heal, but they can also progress to a full rupture without warning.
The key distinction that matters for you: any persistent, uncontrollable wetness that doesn’t smell like urine warrants a call to your provider, even if it seems minor. The volume of the leak doesn’t always reflect the seriousness of the situation.