Hi everyone!

I’m excited to see your posts this week about amniotic fluid. Amniotic fluid should be seen throughout the pregnancy, and often increases during the 1st 2 trimesters, and decreases during the 3rd trimester. It plays many important roles for the fetus, and therefore it is vital that we as sonographers become familiar with the role we play in determining if the amniotic fluid is normal. 

To go along with Dr. Wilson’s questions this week, here are some other questions I thought might be useful in getting us talking about amniotic fluid:

1. What are some roles that amniotic plays (Why are we so concerned about measuring it)?

2. What terms are used to describe excessive and insufficient amniotic fluid?

3. What are some key guidelines we must follow in order to obtain the most accurate AFI possible?

4. Do you have any questions regarding amniotic fluid? Post them below, we’re all trying to figure this all out! (:

Both maternal and fetal factors can cause amniotic fluid levels to be too high, causing polyhydramnios, although about 50% of the time it’s idiopathic. Some causes can be diabetes, RH incompatibility (condition that occurs during pregnancy if a woman has Rh-negative blood and her baby has Rh-positive blood), preeclampsia (pregnancy complication characterized by high blood pressure and signs of damage to another organ system, most often the liver and kidneys), congestive heart failure, certain infections, fetal anomalies and many others like trisomy 18 and 21.

The way this condition affects the fetus depends on the etiology. The cause could be mechanical obstruction, where the baby can’t swallow, or obstruction in the duodenum of the esophagus. Or it could be due to fetal anomalies (which I believe are intrinsic)? These may include anencephaly, meningocele, encephalocele, hydrocephaly, and hydranencephaly. With cranial anomalies, the fetus may not be able to swallow, and might essentially be largely inactive. 

This YouTube video shows a fetal ultrasound with anencephaly (I think you can see the majority of the brain just fully exposed lacking skull), and polyhydramnios. 

https://www.youtube.com/watch?v=cjv_Gyu8DHE

I found this article that explains some of the complications that may occur, specifically if the polyhydramnios is due to over extension of the uterus. They include preterm labor, umbilical cord prolapse and abnormal fetal presentation.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964358/

Some causes of insufficient amniotic fluid (oligohydramnios) include PROM (premature rupture of membranes), or leaking membranes which may cause an increased risk of infection and fetal demise. IUGR (intrauterine growth restriction) may also cause oligohydramnios, because the baby is not thriving and not producing enough fluid/swallowing. Urinary anomalies such as renal agenesis which may cause Potters syndrome. Other urinary anomalies contributing to oligohydramnios may include renal obstruction which may prevent the bladder from emptying. 

Amniotic fluid fills the amniotic cavity that surrounds the developing fetus. It is produced by the cells that line the amnion during the first trimester. Once the fetus has developed kidney function, most of the amniotic fluid is produced from urination. The fluid is then ingested by the fetus to maintain a balance. 

This fluid provides many functions for the fetus. It provides cushion, allows for movement of the fetus, and aids in lung development. Without a proper amniotic fluid volume these functions may be impeded. 

There are several issues that may affect the AF volume. If the fetus has an abnormality in its kidneys and cannot produce urine, then the volume may be too low. This low volume of amniotic fluid is referred to as oligohydramnios and can cause compression of the fetal organs and it can increase the chances of having a preterm birth.

There can also be too much amniotic fluid which is known as polyhydramnios. This may be due to a fetal abnormality where the fetus cannot swallow the fluid, thereby it is unable to balance the fluid that is produced by urination. Polyhydramnios can lead to preterm labor or premature rupture of the membranes.

A sonographer will need to determine the amniotic fluid index (AFI) by measuring the amount of fluid in 4 quadrants around the fetus. This volume will allow the sonographer to assess rather quickly the overall state of the amniotic cavity because they will be able to see if the amount is too high or too low, and this may lead them to look for other developmental issues in the fetus.

I’m having a little bit of difficulty defining what are considered “mechanical obstructions'' and what are the “intrinsic issues'' which can affect amniotic volumes. Maybe someone could explain the difference between these? :)

Amniotic fluid plays an important role in pregnancy. It serves as a cushion, prevents adhesions, and aides in lung development and symmetrical fetal growth. During the first trimester, the fluid (98% water, 2% solids) is secreted by the amnion. Once the fetal kidneys start functioning, they produce much of the amniotic fluid via urination.

• There can be too much amniotic fluid. This is termed polyhydramnios. It occurs when the amniotic fluid index (AFI) is above 24cm. This can result in preterm labor, fetal malpositioning (ex. breech), PROM (premature rupture of membranes), umbilical cord prolapse, and more.
• There can be not enough amniotic fluid. This is termed oligohydramnios. This is determined at a measurement of less than 500mL of fluid. It be caused by PROM, IUGR, renal issues and urinary abnormalities (see below). It can result in Potter's Syndrome, pulmonary hypoplasia, increased risk of stillborn, and compression of fetal organs.

An example of an intrinsic issue affecting amniotic fluid volume is bilateral renal agenesis. As previously mentioned, the kidneys take over a lot of the amniotic fluid production through urination. If the fetus does not develop kidneys, it can result in oligohydramnios. Additionally, bilateral renal agenesis is not compatible with life. Another intrinsic cause of oligohydramnios is  fetal swallowing issues as this also prevents the cycle of fluid through the fetal kidneys. Conversely, polyhydramnios can be caused by maternal diabetes or fetal genetic anomalies.

Oligohydramnios can also result if there is a mechanical obstruction in the fetal urinary system. Examples of obstruction include obstructive ureterocele, ureteral stricture, and persistent cloaca.

I suspect many sonographers can sweep through an OB scan and already have a sense for whether or not there is enough amniotic fluid. We always measure to calculate AFI, but because the anechoic amniotic fluid provides an acoustic window for visualizing the fetus, it is something that should be noticed right away.

I'm not sure why, but this discussion board question set seemed harder for me. Did anyone else feel that way? I'm not 100% confident in my post, so please respond if something doesn't sound right to you. I'm curious to see if anyone found other etiologies for oligo/polyhydramnios.

Amniotic fluid serves an essential purpose for the growing fetus, just as water does to human life. It's important that the levels are balanced to ensure the conceptus is receiving just the right amounts. After all,you can have too much of a good thing. 

If too much amniotic fluid is present we run the risk of the fetus developing polyhydramnios which may lead to preterm labor or a malpositioned fetus in the womb. On the other spectrum, if the fluid levels are too low the conceptus could have oligohydramnios.

One major complication associated with oligohydramnios is underdeveloped fetal lungs since amniotic fluid supports growth.

When it comes to polyhydramnios there are multiple potential causes, one of which is maternal influences. Some of these include maternal diabetes, infection occurring during the course of the pregnancy, or even RH incompatibility. If polyhydramnios is not caused by the mother it could be a result of fetal abnormalities. In this instance the fetus may have difficulty ingesting the fluids due to an obstruction or malfunction within its cranial activity.

Similar factors can apply to oligohydramnios as well. If there is a ruptured membrane and fluid has the ability to seep out or if the baby is able to consume the amniotic fluid but has a hard time excreting it due to renal agenesis or a bladder obstruction.

This is why it is extremely important to take an amniotic fluid index during the sonogram. By dividing the mother's belly into quadrants and measuring the depth of each section we can quantify the amount of amniotic fluid present. As sonographers we should know right away based on the numerical value of the quadrants if the fluid is normal or showing signs of polyhydramnios or oligohydramnios!

Heres a great video that explains both poly and oligohydramnios in an easy to remember way! https://www.youtube.com/watch?v=gjN83EyWd6s

There are multiple factors that may affect the levels of amniotic fluid such as maternal factors or fetal factors. The varying levels of AF is called polyhydramnios which is when fluids are really high. This can be seen when there is more than 2000 -3000 ml in the 3rd trimester and an indicator of possible fetal abnormality. A cause for this is when the fetus is unable to absorb as much fluid as being produced however 50% of the time it is unknown as to why this is caused. Maternal causes include diabetes , RH incompatibility, or pre-eclampsia. When a large amount of AF is produced PROM can happen which is also known as premature rupture of membrane. I saw this in clinicals!!! (The patients water ruptured early and there was no AF surrounding the baby)  

Low levels of amniotic fluid is called oligohydramnios when there is less than 500 ml of amniotic fluid. (I am not sure what trimester this would be considered low in) Some causes of this is premature rupture of membranes or intrauterine growth restriction. Some fetal causes are structural urinary abnormalities which is renal genesis and renal obstruction. 

To measure amniotic fluid the sonographer should separate the uterus into four cavities and measure the largest part of fluid from AP in each quadrant. This is called AFI (amniotic fluid index) Color should be thrown on to ensure there is not umbilical cord in the anechoic space. After adding all of these up I believe they should come to about 8 cm and polyhydramnios is about 20 cm. I hope I answered these questions correctly and thoroughly please let me know if I missed anything. 

This is a picture of Oligohydrmanios, I found one for PROM but for some reason it won't show when I upload basically it looks like a baby with NO surrounding fluid. 

The amniotic fluid is such a vital aspect of a thriving fetus. Amniotic fluid is produced by the kidneys and is ingested by the fetus. The amount of production and reabsorption must be equally maintained in order for proper function to occur. If production or reabsorption isn’t consistent then problems unfortunately occur. If the fetus is having difficulty digesting the amniotic fluid then there will be polyhydramnios, which is an abundance amount of amniotic fluid around the fetus. Polyhydramnios usually indicates an abnormality or the baby could just be large for gestational age. A lot of maternal health problems can contribute to Polyhydramnios such as diabetes, congestive heart failure, and sometimes even preeclampsia. It stated about 30% of the time polyhydramnios was related to a fetal abnormality such as cerebral or GI issue.

 On the other hand Oligohydramnios is a lack of amniotic fluid with only about 500ml, which tells us something is wrong. It may be premature ruptured membranes which would also bring a possible increase of infection and fetal demise. Also oligohydramnios is also seen with IUGR which isn’t allowing the baby to do well; The baby often can’t swallow and no fluid is being produced with this condition. Many other conditions could cause a lack of amniotic fluid such as an absence of a kidney, polycystic kidney disease, or any renal obstruction, since the renals play a huge role with the production of amniotic fluid.

It's incredibly important to measure the amniotic fluid index by calculating the amounts of fluid in each pocket free of any objects such as the umbilical cord or fetal parts. One must measure the amniotic fluid in a perpendicular plane in four different quadrants by evenly dividing the maternal belly within 4 sections with an imaginary line. Measuring the biggest pockets and adding them up will determine the amount of amniotic fluid that’s present. A normal range would be about 8cm and polyhydramnios would be considered with a measurement of 20 and 25cm.

Image found of oligohydramnios.

 Image found of polyhydramnios.

Discuss what factors might cause the amniotic fluid levels to be too high or too low and how the various levels could affect the developing fetus.

Amniotic fluid is secreted from the cells that line the amnion in the first trimester. Around 12 weeks gestation the fetal kidneys start to take over and begin to produce fluid. The fetus starts to ingest the fluid and secretes fluid as well. These processes should be somewhat equal. Fluid in equals fluid out. If they are not cycling at equal rates then polyhydramnios (too high) or conversely oligohydramnios(too low) may occur. Polyhydramnios or too much fluid can occur if the fetus is having problems ingesting or swallowing the fluid. If the fetus cannot ingest the fluid, the fluid will build up within the amniotic cavity. Ogliohydramnios on the other hand may occur when the fetal kidneys are having problems. If the kidneys are not functioning properly, amniotic fluid isn’t being made and therefore isn’t being secreted. If the developing fetus has too much or too little fluid this could be problematic for their development. Proper amniotic fluid levels aid in fetal temperature, biochemical homeostasis, allows for fetal movement and fetal growth.

Discuss the idea behind mechanical obstructions vs intrinsic issues that might affect amniotic fluid volumes. Why or how do fluid volumes help sonographers better assess rather quickly and subjectively the overall "feel" of the amniotic cavity. What might be the consequences to a pregnancy with too much or too little fluid? 

Mechanical obstructions are structures within the fetal body that aren’t formed properly that as a result block fluid from entering the fetus. For instance, if the baby can’t swallow or has an obstruction in the esophagus or a GI malformation it cannot ingest the fluid resulting in polyhydramnios. However polyhydramnios can occur intrinsically when there is a cranial abnormality. The fetal parts may be fully developed but the fetal brain is not signaling the fetus to swallow and ingest the fluid.

Fluid volumes help sonographers better assess the overall “feel” of the amniotic cavity by indicating certain abnormalities with polyhydramnios and oligohydramnios. If you see the fetus somewhat floating around you might suspect polyhydramnios. As a sonographer you should think to check for a blockage, infection, cranial issue or circulatory abnormalities as these might be consequences from the excessive fluid. Also check to see if the mother has diabetes or preeclampsia. If you are scanning and find it hard to see the fetus you can suspect oligohydramnios. Consequences of low fluid may be due to a rupture in membranes, fetal demise, IUGR, and renal pathology 

Here is an image showing an issue with the fetal cranium which resulted in polyhydramnios. 

Here is the video that goes along with the image.

https://www.youtube.com/watch?v=YmcKqMV5RbY

Amniotic fluids plays a very vital role during pregnancy; it protects the fetus, helps with long development and allows the fetus to move around. During the first trimester, the cells that line the amnion secrete amniotic fluid and after about 12 weeks the fetal kidneys start producing the fluid as well via urination. There has to be an equilibrium maintained between the rate of production and ingestion of amniotic fluid by the fetus otherwise many problems can occur. The normal range for amniotic fluid is about 8 centimeters once we add up all the four quadrants. 20 to 25 cm means polyhydramnios, which means there is too much amniotic fluid present. One case of this condition could be that the baby is having issues ingesting the amniotic fluid around it so the fluid is just building up instead of being reabsorbed. Also, sometimes maternal causes such as diabetes and preeclampsia could be the cause of excess amniotic fluid. On the other hand, oligohydramnios is when amniotic fluid is less than 5cm This can be caused by membrane rupture which causes the fluid to leak out and even an issue with the fetal kidney causing an obstruction. With too much amniotic fluid, I fear that maybe the placental cord can get compressed and that is how the fetus receives all its nutrients so it can be detrimental. For too little amniotic fluid, the baby would not be able to move around and no input into the kidneys could lead to developmental issues in them.

Polyhydramnios:  

Oligohydramnios:

Beyond 20 weeks the fetus helps maintain fluid volume by swallowing amniotic fluid. Polyhydraminos can occur when a fetal anomaly is present that prevents the fetus’ motor movement of swallowing. Possible anomalies include: GI obstructions, facial tumors, and Dandy-Walker syndrome (cerebellum malformation). Maternal contributions to polyhydraminos include diabetes and uremia. The volume of amniotic fluid becomes highly dependent on fetal output; the fetus can produce 450ml of urine per day (p. 602). Without proper genitourinary system functions, such as renal agenesis or an obstruction in the urinary tract, the fetus is unable secrete fluids resulting in oligiohydraminos. Premature prelabor rupture of membranes (PPROM) also can result in oligiohydraminos. To my understanding in this case the amniotic fluid may essentially be loosing its volume through the rupture. Amniotic fluid plays a crucial role in fetal development of lungs, digestive system, skeletal muscles, and bones. Considering this oligiohydraminos can hinder growth in each of these areas. This highlights the importance of the sonographer properly assessing the AFI (in four quadrants), an AFI of less than 5.0 cm is a concern. In addition, I found it interesting that the amniotic fluid can appear echogenic due to vernix caseosa (p. 601). Vernix caseosa is essentially a coating that protects the fetus’ skin. 

 Here’s some interesting reads that discuss amniotic fluid:

https://fetalmedicine.org/education/fetal-abnormalities/amniotic-fluid/oligohydramnios

https://teachmeobgyn.com/pregnancy/fetal-abnormality/oligohydramnios/

And Vernix Caseosa:

 https://www.healthline.com/health/pregnancy/vernix-caseosa

The amniotic fluid is a very critical part of fetal development. The AF helps cushion, lubricate and nourish the fetus. The fluid also is a space where the fetus can freely grow and learn muscle and motor skills while moving around. It is no wonder that too much or too little could be catastrophic.

When there is too little AF, this is known as oligohydramnios, and is usually caused by premature ruptured membranes, poor fetal growth, post-term pregnancy, problems with urinary tract development, drugs, etc. This would be discovered either by ultrasound or actual leaking fluid. This would require delivering the baby asap or amniotransfusion. During the first 6 months of pregnancy this can cause stillbirth, birth defects, miscarriage, and premature birth.

Where there is too much AF this is called polyhydramnios, typically caused by maternal diabetes, GI or swallowing problems of the fetus, or possibly even heart problems or infection of fetus. Mother could take medications to treat, or get amnioreduction, or deliver the baby. Severe polyhydramnios can cause malposition, premature birth, ruptured membranes, umbilical cord prolapse, heavy bleeding during birth, and even fetal demise.

Sonographers measure the AFI to check for fluid level, but a seasoned sonographer may just be able to tell right away after a quick sweep whether fluid levels look "off."

I found a great short video that explains more about amniotic fluid and its composition (is this the same guy as in Sue's videos?? I can't tell haha):

https://www.youtube.com/watch?v=zjD9Ky4zFME&ab_channel=TodayIFoundOut

Polyhydramnios, too much amniotic fluid, could be caused for a plethora of reasons but <50% are idiopathic. Causes can come from the maternal aspect and others from the fetal aspect. Some maternal causes can be diabetes, RH incompatibility, preeclampsia, etc. Fetal causes can be, multiple gestation, grossly malformed fetus, Circulatory abnormalities, the fetus can't absorb the fluid, and more. This can lead to preterm labor or PROM (premature rupture of membranes)

Oligohydramnios, too little amniotic fluid, is present when there is less than 500ml of fluid seen. Some causes are PROM, IUGR, Structural urinary abnormalities, post maturity/post term pregnancy, fetal demise and more. It can lead to increased risk of infection, fetal demise, and this website mentions other complications like cerebral palsy, preterm birth, and cord compression.

https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/maternal-medical-conditions/oligohydramnios/

Mechanical obstructions affecting AF levels can be obstruction in the duodenum or esophagus, which isn't allowing the fetus to swallow, thus not ingesting the fluid which can lead to either polyhydramnios or oligohydramnios, it can also be caused from renal issues because not enough fluid will be made. Intrinsic issues have to do with cranial abnormalities that also prohibit the fetus from swallowing.  

Measuring amniotic fluid is extremely important, all four quadrants from be measured perpendicular to the lay of the belly, free of cord at the deepest part. Adding up all four should equal to around 8-24 cm. The right amount of fluid provides a window to see the fetus, it would be obvious to the sonographer that theres too little fluid just by that aspect. I saw this today in clinic, 34 weeks with no fluid and it was difficult to get a good window to measure babies head. 

Howdy Friends,

Amniotic fluid basics: Amniotic fluid volume is increased in the first trimester (made by cells lining amnion) and second trimester (12 weeks, made mostly by fetal kidneys via urine), and it tends to slightly decrease in the third trimester. This fluid should always exist around a developing fetus. Vernix (cells/secretions) can be seen floating in amniotic fluid.

Possible causes of oligohydramnios (<500mL): Membrane rupture/leak, intrauterine growth restriction, renal agenesis/obstruction

Possible results of oligohydramnios: Fetal demise, high likelihood of infection

Possible causes of polyhydramnios: Fetal: Inability to swallow to due to mechanical or intrinsic issue, GI anomalies, neural tube defects. Maternal: diabetes, pre-eclampsia (sometimes), congestive heart failure, and infections. Possible due to multiple gestations, a malformed fetus, teratomas, etc.

Possible results of polyhydramnios: Fetal malposition, maternal breathing issues, premature birth, stillbirth.

Intrinsic issues: Trouble swallowing amniotic fluid due to neurological/cognitive issues

Mechanical issues: Trouble swallowing due to obstruction or inability to absorb the fluid

This page on Mayoclinic was helpful. 

https://www.mayoclinic.org/diseases-conditions/polyhydramnios/symptoms-causes/syc-20368493

Sarah

Amniotic fluid is vital to a developing fetus and successfully carrying a pregnancy to term. The amount of amniotic fluid surrounding the fetus can differ from normal, and it is important for the sonographer to know what each fluid sign can signal in the developing fetus.

Polyhydramnios is when there is excess (above 24cm)  amniotic fluid around the fetus. 50% of polyhydramnios is of unknown origin. Some maternal causes are diabetes, congestive heart failure, and infections. Sometimes (30%) the issue is a fetal abnormality such as the fetus cannot swallow, making the intake of amniotic fluid into the fetus impossible. Polyhydramnios can lead to a premature birth or malpositioned fetus.

On the other hand, oligohydramnios is when there is not enough (<500ml) amniotic fluid. This may be from a premature rupture of the membrane, which could lead to infection or fetal demise. IUGR may cause oligohydramnios as well since they do not thrive as they should. Urinary abnormalities in the fetus can lead to oligohydramnios since the fetus takes amniotic fluid in through swallowing and it must go through the renals and urinary system to be sent out once again. Renal agenesis, bladder obstructions, or ureteroceles are some fetal urinary issues that may lead to oligo. Due to the absence of enough amniotic fluid, infection, urinary defects, PROM, or even demise may occur.  

If I am understanding correctly, a mechanical obstruction may be things such as baby not swallowing correctly leading to polyhyrdamnios, while intrinsic factors may be cranial abnormalities that lead to development not proceeding as normal. I would love some more information on mechanical vs. intrinsic because I'm pretty sure I'm not understanding it completely!

Amniotic fluid levels help the sonographer to understand the feel of the amniotic cavity because it quickly and easily signals the health of the fetus not only in the uterus, but the health of its developing organs and further development outside the womb even. Both too much and too little amniotic fluid points to abnormalities that can be examined and detected prior to delivery just by checking the fluid around the fetus, so it is important to measure and be able to identify when it looks abnormal.

• Amniotic fluid is what fills the amniotic cavity. It surrounds the developing fetus like a cushion and prevents adhesions. During the first and second trimester the amniotic fluid will be increased. Although, during the third trimester, the fluid will decrease. Amniotic fluid is produced by the cells that line the amnion during the first trimester. However, most of the amniotic fluid is then produced from urination once the fetus has developed their kidney function. 

• Mechanical obstructions may indicate a problem with the fetus gastrointestinal tract. A decreased or sudden stop of AF flow in the intestine can cause it to dilate. Intrinsic issues, problem relating to inherent, are when/ if the mother is experiencing hypertension, dehydration, or diabetes, etc. All these issues on the mother can affect the fetal amniotic fluid levels. Fluid volumes help sonographers better assess rather quickly and subjectively the overall "feel" of the amniotic cavity because too much or too little within the 4 quadrants around the fetus is alarming and should lead them to look/sweep through for other developmental issues in the fetus. When the volume of amniotic fluid is too low, it is called oligohydramnios. Oligohydrmnios can cause an distinct compression of the fetal organs and may also cause the risk of having a preterm birth. When the volume of the amniotic fluid is too high, it is called polyhydramnios. Polyhydramnios may increase the chances of a preterm labor and/or a premature rupture of the membranes (PROM).

https://www.ucsfbenioffchildrens.org/conditions/fetal_bowel_obstruction/

https://www.premierhealth.com/your-health/articles/women-wisdom-wellness-/amniotic-fluid-too-much-or-too-little#:~:text=Issues%20with%20the%20mother%3A%20Hypertension,can%20affect%20amniotic%20fluid%20levels.

I definitely STRUGGLED with this discussion post. The resources above helped me out, I hope it can do the same for you!

The presence of too much amniotic fluid (> 2,000 mL)  is called polyhydramnios. Causes of polyhydramnios can be attributed to complications with the mother, the fetus or an unknown cause. Some maternal issues that can lead to polyhydramnios are blood type mismatches (Rh) and pre-eclampsia. Some fetal causes of polyhydramnios are a congenital blockage of the GI tract and anemia. Polyhydramnios causes the mother’s uterus to enlarge, which can displace and compress other organs in or adjacent to the abdominopelvic cavity. The risks include preterm labor, premature rupture of membranes, and placental abruption.

The lack of adequate amniotic fluid (< 500 mL) is called oligohydramnios. Its causes can include congenital anomalies with the urinary system, premature rupture of membranes, maternal dehydration and hypertension. Some complications associated with oligohydramnios are intrauterine growth restriction, incomplete or delayed lung maturation, and fetal death. 

As seen with some of the causes listed above, there are mechanical obstructions that affect amniotic fluid volume. These include physical blockages or malformations that prevent the fetus from ingesting amniotic fluid or producing/excreting fluid, such as esophageal atresia (the upper and lower esophagus don’t fuse) or posterior urethral valve (tissue covering the urethra). Intrinsic causes of suboptimal amniotic fluid levels can be related to maternal blood. If the maternal blood supply cannot provide the nutrients and oxygen needed for the fetus to thrive, it will affect how the fetus can produce and recycle amniotic fluid. Some examples include maternal diabetes (excess blood glucose) and hypertension (decreases blood flow to placenta). 

The clinical way to estimate amniotic fluid volume is called amniotic fluid index (AFI). AFI requires the imaginary division of the uterus into four quadrants. The deepest pocket of amniotic fluid devoid of all fetal structures will be measured in cm and added together to get the AFI. Normal values range from 5 cm - 25 cm. As we scan more OB patients, I’m sure we’ll have a good eye for making snap judgments about abnormal amniotic fluid levels. We use the amniotic fluid as a window to see the fetus so we’ll be able to catch on when the window is minimized or too large. 

Here is a link to a site showing ultrasound images of abnormal amniotic fluid, including polyhydramnios and oligohydramnios. Below is one of images from a severe case of oligohydramnios. 

Amniotic fluid is what surrounds the baby in the amniotic cavity. The amniotic fluid is very important to the baby's health and well-being. This fluid is what helps develop the baby's limbs, lungs, digestive system, and muscles. The placenta could actually be a cause of amniotic fluid issues. If the placenta is not providing enough blood and fluid to the baby, the baby cannot recycle the fluid. the baby's kidney may also not be able to produce enough urine, which in turn means lower fluid levels. Too much amniotic fluid is called polyhydraminos, while too little amniotic fluid is called oligohydraminos. A common cause of polyhydramnios is maternal diabetes, which would cause too much fluid around the baby and be considered a high risk pregnancy. Another cause for Polyhydramnios could be a twin pregnancy. One twin could receive too much blood and nutrients while the other receives too little. In order to accurately measure the amniotic fluid volume which is known as the AFI, the sonograpgher must divide the the uterus into four quadrants and measure the largest pocket of amniotic fluid in each quadrant. I believe a normal measurement is around 8cm and Polyhydramnios is from 20cm - 25cm, which is a major difference that as sonographers we should be able to detect. I also learned today that it's important to look at the mother's cervix if there is suspicion of oligohydraminos because, the cervix could be dilated to wide or there could be an absence of a mucous plug which would cause the amniotic fluid to leak out of the cervix.

The following is a sonogram of twins with baby A suffering from oliohydraminos and baby B suffering from polyhydramnios.

Hey guys!

By the second trimester, amniotic fluid is basically a recycling system. The baby swallows the AF, pee's it out, and then repeats the process. It sounds gross, I know. It's always a fun little fact to tell the parents. They think it's funny!