What does my amniotic fluid index mean?

An AFI between roughly 5 cm and 24 cm is the range most commonly cited as normal in the third trimester. Below about 5 cm is generally classified as oligohydramnios (low fluid), and above about 24 cm as polyhydramnios (high fluid). Those 5 and 24 cm figures are widely used published cut-points, but they're not magic lines: the exact normal range shifts a little across gestation, some clinics use slightly different numbers, and a value near a threshold is often simply re-checked. Whatever your AFI, it's read in the context of your gestational age and the rest of the scan — the number alone isn't the answer.

A low AFI means there's less amniotic fluid measured than expected, and it's the kind of result a provider looks at closely — but on its own it is not a diagnosis. It usually prompts a closer look: repeating or confirming the measurement, checking how the baby is growing and moving, looking at the placenta and blood flow, and considering the gestational age. There are many possible reasons for lower fluid, some of which matter and some of which don't, which is exactly why it needs a clinician rather than a calculator. If your report shows a low AFI, contact your OB or midwife so they can interpret it in context — don't wait on a single number.

A high AFI means more amniotic fluid was measured than expected. Like a low result, it isn't a diagnosis by itself — it's a flag that usually prompts closer monitoring and a search for a cause. Many pregnancies with a mildly high AFI are entirely fine, and often no specific cause is found; sometimes it points to something your provider will want to check. The right next step is a conversation with your OB or midwife, who reads the AFI alongside your gestational age, the baby's growth and anatomy, and the rest of the scan. This tool can tell you which side of the published cut-point you're on; it can't tell you why, and it isn't meant to.

They're two ways of estimating amniotic fluid on ultrasound. The amniotic fluid index (AFI) adds up the deepest vertical fluid pocket in each of four quadrants of the uterus, giving a single number in centimetres — that's what this tool interprets. The single-deepest-pocket method (SDP, sometimes called maximum vertical pocket or MVP) measures just the one deepest pocket and has its own, different normal range. Neither is universally 'better'; clinics choose based on their protocols and the situation. If your report lists an SDP or MVP rather than an AFI, the 5 and 24 cm cut-points here don't apply — ask your provider which measurement they used and what it means for you.

It's a useful measurement, but it's a snapshot, not a precise gauge. AFI can vary with the sonographer's technique, the baby's position, the time of day and hydration, and it changes gradually across pregnancy. Because of that, a value close to a cut-point is often simply re-measured or re-checked at a follow-up scan rather than acted on straight away, and providers pay attention to the trend and the whole clinical picture as much as to any single figure. Treat the band this tool shows as a starting point for a conversation with your provider, not as a fixed verdict about your pregnancy.

Yes. This tool runs entirely in your browser: the numbers you type are added up and compared to the published cut-points on your own device, and are never sent to a server, stored, or shared — close the tab and they're gone. We treat pregnancy data as sensitive by design, so there's nothing to delete and no account involved. The result is general educational information based on published thresholds; it isn't medical advice or a diagnosis, and it can't replace the sonographer's report or the OB or midwife who reads it in context.