Drinking more water is the simplest and most effective way to increase amniotic fluid, with studies showing that drinking 2 liters over 2 hours can raise amniotic fluid index (AFI) by nearly 4 cm. But how much fluid increases and what else can help depends on why levels are low in the first place. Low amniotic fluid, called oligohydramnios, affects roughly 4% of pregnancies and is most common in the third trimester.
Why Amniotic Fluid Drops
Amniotic fluid isn’t static. Your baby constantly swallows it, urinates it back out, and the cycle continues. Anything that disrupts this loop can lower fluid levels. The most common causes include:
- Dehydration: When you’re not drinking enough, your body has less fluid available for the amniotic sac.
- Placental problems: A placenta that isn’t delivering enough blood and nutrients to the baby can reduce fluid production.
- Fetal kidney or urinary tract issues: Since the baby’s urine makes up a large portion of amniotic fluid in later pregnancy, developmental problems with the kidneys or urinary tract can lower output.
- Premature rupture of membranes (PROM): A small tear in the amniotic sac can cause a slow, steady leak that gradually depletes fluid.
- Going past your due date: Fluid levels naturally decline after 40 weeks, sometimes significantly.
- Preeclampsia or high blood pressure: These conditions reduce blood flow to the placenta, which in turn reduces fluid production.
The cause matters because it determines which strategies will actually work. Dehydration responds well to oral fluids. A slow membrane leak does not. Your provider will typically use ultrasound to measure your AFI and look for the underlying reason before recommending a plan.
How Oral Hydration Works
Maternal hydration is the most studied and most accessible intervention. In a key clinical trial, women with oligohydramnios in the third trimester who drank 2 liters of water over a 2-hour period saw their AFI increase by an average of 3.8 cm. That’s a meaningful jump, often enough to move someone from a concerning range back into a reassuring one. The mechanism is straightforward: extra fluid in your bloodstream increases blood flow to the uterus and placenta, which boosts the baby’s urine production.
Researchers also tested intravenous fluids in the same study and found that IV hydration with a low-salt solution produced a similar increase of about 2.8 cm. Oral water actually performed slightly better, which is encouraging because it means you don’t need a hospital visit to get results. The effect is temporary, though. Staying consistently well-hydrated throughout the day matters more than a single large intake. Most providers recommend aiming for 8 to 12 cups of water daily in the third trimester, with more if you’re active, live in a warm climate, or have been diagnosed with low fluid.
L-Arginine Supplements
L-arginine is an amino acid that helps widen blood vessels by boosting production of nitric oxide, a natural compound that relaxes artery walls. When blood vessels in the placenta relax, more blood reaches the baby, and fluid production increases. A clinical study of pregnant women with oligohydramnios found that L-arginine raised AFI from an average of 6.8 cm to 9.4 cm over roughly 3 weeks. That’s an increase of about 2.6 cm, and 85% of the women in the study saw improvement.
These results are promising, but L-arginine isn’t something to start on your own. Dosing, timing, and whether it’s appropriate for your specific situation all depend on factors your provider can assess. It’s most commonly used in cases where placental blood flow appears to be the issue.
Bed Rest and Positioning
You may have heard that lying on your left side improves blood flow to the uterus. The idea has been around for decades: in theory, the left lateral position takes pressure off a major vein (the inferior vena cava) that runs along the right side of your spine, allowing more blood to return to your heart and flow to the placenta. Observational studies have supported this concept in general terms.
In practice, the evidence is less convincing. An MRI study found no significant increase in blood flow through the inferior vena cava when patients shifted from lying on their back to a 15-degree left tilt. And a Cochrane review of bed rest for fetal growth found only one qualifying study from 1987, which showed no meaningful difference between women on full hospital bed rest and those who rested only on weekends. The medical consensus is that prolonged bed rest hasn’t been shown to reliably improve amniotic fluid levels, and it carries its own risks, including blood clots and muscle loss.
That said, avoiding prolonged time flat on your back in late pregnancy is still reasonable. Sleeping on your side is more comfortable for most women and may support better circulation, even if the fluid-boosting effect is modest.
Amnioinfusion: A Clinical Procedure
When fluid levels are critically low and the baby is showing signs of distress, particularly during labor, your provider may perform an amnioinfusion. This is a direct approach: room-temperature saline is infused into the uterus through a thin catheter inserted through the cervix, which needs to be dilated at least 1 to 2 centimeters. The process takes 10 to 30 minutes.
Amnioinfusion is most commonly used during labor when low fluid causes the umbilical cord to compress, leading to drops in the baby’s heart rate. It can also dilute meconium (the baby’s first stool) that has been released into the fluid, reducing the risk of the baby inhaling it during delivery. In cases of very early membrane rupture, before the third trimester, amnioinfusion may be used to buy time for the baby’s lungs to develop. The procedure has a high success rate, and outcomes tend to be better when the starting fluid level is lower, meaning there’s more room for improvement.
Signs Your Fluid May Be Leaking
Sometimes amniotic fluid drops because the sac has developed a small tear. The tricky part is that amniotic fluid can be easy to confuse with urine or normal vaginal discharge. A few features can help you tell the difference. Amniotic fluid is thin and watery rather than thick or sticky. It’s typically clear or pale yellow and has no strong odor. The key giveaway: you can’t stop it. Unlike urine, which you can hold or slow with a kegel, amniotic fluid continues to leak, often in small gushes that may coincide with movement or contractions.
If you notice persistent dampness that doesn’t seem like discharge or urine, it’s worth getting checked. A simple test at your provider’s office can confirm whether the fluid is amniotic.
What Monitoring Looks Like
Once low fluid is identified, your provider will likely increase the frequency of ultrasound checks to track whether levels are stable, improving, or declining. In more complex cases, where low fluid accompanies fetal growth restriction or abnormal blood flow patterns, monitoring may increase to twice weekly. These checks typically include a biophysical profile, which assesses the baby’s movement, breathing, muscle tone, and fluid level together to get a fuller picture of well-being.
When low fluid persists despite hydration and other interventions, the timing of delivery becomes the central question. In many cases, especially past 37 weeks, early delivery is safer than continuing to manage declining fluid. Before 37 weeks, providers weigh the risks of prematurity against the risks of staying pregnant with very low fluid, making decisions on a case-by-case basis.