Amniotic fluid is the liquid that surrounds a fetus in the womb. It has a range of functions, all of which relate to the development of the fetus.
The fetus and fluid stay in the amniotic sac, which usually breaks when a woman goes into labor. It can sometimes rupture early, which is called premature rupture of membranes (PROM).
In this article, learn about the signs that amniotic fluid is leaking, the common causes of PROM, and when to speak to a doctor.
Leaking amniotic fluid might feel like a gush of warm fluid or a slow trickle from the vagina. It will usually be clear and odorless but may sometimes contain traces of blood or mucus.
If the liquid is amniotic fluid, it is unlikely to stop leaking.
Signs that it is not amniotic fluid
The uterus sits on the bladder during pregnancy, so it is not uncommon for pregnant women to leak urine. If the discharge smells like urine, it probably is.
Women may also experience an increase in vaginal discharge during pregnancy. Normal discharge tends to have a mild smell and look milky.
If the fluid does not appear to be urine or discharge, it is best to speak to a doctor.
Women who also experience the following symptoms should seek medical attention too:
- foul-smelling, brown or green discharge from the vagina
- the uterus feeling tender
- rapid heart rate
- a decrease or lack of increase in weight
While waiting for medical attention, a woman should not use tampons, have sex, or do anything else that might introduce bacteria into the vagina.
A doctor may take a sample of the fluid to determine whether it is amniotic fluid. They may also carry out tests to determine the cause of the leak.
These tests could include a vaginal exam to see if the cervix is dilating and the woman is in labor. An ultrasound can help doctors check how much fluid is surrounding the baby.
They may also perform a dye test, which involves introducing blue dye into the amniotic sac and asking the woman to wear a sanitary pad. If the dye shows up on the pad, this can indicate leaking amniotic fluid.
The amniotic sac ruptures when a woman goes into labor. People often refer to this as the water breaking.
According to the American Pregnancy Association, just one in 10 women will experience a "dramatic gush" of amniotic fluid. For most women, it is more likely to feel like a constant trickle.
Sometimes, the amniotic sac breaks or leaks before labor starts. If the amniotic sac breaks before the 37th week of pregnancy, doctors refer to it as preterm PROM.
Women who got pregnant less than 6 months after their last labor or are carrying more than one baby have a higher risk of PROM.
Other factors that can lead to PROM are:
- contractions that put pressure on the amniotic sac, causing it to tear
- the amniocentesis needle making a hole that takes too long to heal
- cerclage, a procedure where doctors stitch the cervix closed until the baby is ready for delivery
- a urinary tract infection (UTI) or sexually transmitted infection (STI)
- medical conditions, such as lung disease and Ehlers-Danlos syndrome
- exposure to harmful substances, including tobacco, illicit drugs, and alcohol
- too much or too little amniotic fluid
- the placenta separating from the uterus
Treatment will depend on the cause of the leak, as well as the age, health, and development of the fetus.
A doctor may recommend bed rest, meaning that the woman should reduce her activities and rest for most of the day. They may also advise abstaining from sex.
If a woman has an infection, a doctor will prescribe antibiotics that are safe to take during pregnancy.
If the baby is ready to be born, doctors may choose to initiate labor using a drug called oxytocin. Alternatively, medications called tocolytics can help stop premature labor if it is too early for the birth to occur.
About 12 days into pregnancy, an amniotic sac forms around the growing fetus. Amniotic fluid fills the sac and has several purposes, including:
- protecting and cushioning the fetus
- keeping the fetus at a steady temperature
- allowing the fetus to breathe in the fluid while the lungs grow and develop
- helping the fetus's digestive system grow and develop as they swallow the liquid
- assisting the muscle and bone development of the fetus as they move around in the fluid
- protecting the umbilical cord, which carries food and oxygen from the placenta to the fetus
The amniotic fluid comprises mainly water for the first 20 weeks of pregnancy. After that, it also contains nutrients, hormones, antibodies, and the baby's urine.
The quantity of fluid in the amniotic sac tends to increase until around the 36th week of pregnancy when it starts to decrease. At its peak, there is about 1 quart of amniotic fluid inside the sac.
It is not unusual for women to experience more vaginal discharge than usual during pregnancy. Vaginal discharge will typically smell mild and appear milky. Women may also leak urine when they are pregnant.
A pregnant woman with a liquid other than urine or normal discharge coming from the vagina should visit the doctor. This is particularly true if the fluid is green, brown, or has a foul smell.
Leaking amniotic fluid will usually be clear and odorless and will continue to leak.