Amniotic fluid index (AFI) is a quantitative estimate of

amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwee ...

and an indicator of fetal well-being. It is a separate measurement from the biophysical profile. AFI is the score (expressed in

centimetres upright=1.35, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is in-between 1 meter to 1 millimeter. A centimetre (International spelling) or centimeter (American ...

) given to the amount of amniotic fluid seen on ultrasonography of a pregnant

uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...

. To determine the AFI, doctors may use a four-quadrant technique, when the deepest, unobstructed, vertical length of each pocket of fluid is measured in each quadrant and then added up to the others, or the so-called "single deepest pocket" technique. An AFI between 8 and 18 cm is considered normal. Median AFI level is approximately 14 cm from week 20 to week 35, when the amniotic fluid begins to reduce in preparation for birth. An AFI smaller than 5–6 cm is considered as oligohydramnios. The exact number can vary by gestational age. The fifth percentile for gestational age is sometimes used as a cutoff value. An AFI larger than 24–25 cm is considered as polyhydramnios.

Causes of low amniotic fluid

There are many things that can cause low AFI, these include: * Leaking or rupture of membranes: Leaking or rupture of membranes may be caused by a gush of fluid or a slow constant trickle of fluid. This is due to a tear in the membrane. Premature rupture of membranes can also result in low amniotic fluid levels. * Placental problems:

Placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

l problems may cause low amniotic fluid. If the placenta is not providing enough blood and nutrients to the baby, then the baby may stop recycling fluid. * Birth defects: Birth defects may occur if the fetus has problems with the development of the

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

s or urinary tract, which could cause little urine production, and it can lead to low levels of amniotic fluid. * Maternal complications: Maternal complications may cause low amniotic fluid. Some factors such as

hypertension Hypertension, also known as high blood pressure, is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not cause symptoms i ...

diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...

dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

, preeclampsia, and chronic hypoxia in a woman can have an effect on amniotic fluid levels.

References

Tests during pregnancy {{human-repro-stub