Fundal-Symphysis Height (FSH)
|Fundus is the medical term for the upper portion of the uterus between the fallopian tubes. Fundal height is a measure of the size of the uterus, fetal growth and development. Most caregivers will record their patient's fundal height on every prenatal visit. Measuring the fundal height can be an indicator of proper fetal growth and amniotic fluid development.|
Fundal height is a measurement used to estimate the gestational age of a fetus/baby. Fundal height is not considered to be a very accurate measurement to determine baby's weight. Ultrasound is far more accurate but still has a margin for error.
Doing the measurement.
Essentially, measuring the fundal height involves the woman lying down (it is not meant to be done with the woman in a standing or sitting position) and her caregiver placing the end of the measuring tape on her pubic bone (symphysis pubis). The symphysis pubis bone is situated just below the pubic hair line in the middle. The length of tape is then positioned up the middle of the woman's belly with the measurement taken from where the tape reaches the top of her uterus or fundus, giving a fundal height in centimetres (cms).
The measurement in centimeters and should closely match the fetus gestational age in weeks, within 1 or 2 cm, e.g., a pregnant woman's uterus at 22 weeks should measure 20 to 24 cm.
Two measurements 2 weeks apart showing a deviation of more than 2 cm may indicate that the fetus is large or small for dates, that the estimated gestation is in error, or that the woman is carrying a multiple pregnancy.
A shorter measure can happen for one of the following reasons:
The fundus reaches the mother's naval by 20 weeks of pregnancy, the diaphragm (the muscle that extends across the bottom of the ribcage) by 36 weeks and then drops down again as the baby engages in the pelvis.
Fundal heights tend to be used from about 16 to 37 weeks of pregnancy, with their greatest benefit believed to be between 22 to 34 weeks. A text book fundal height in centimetres is supposed to equal the same amount of weeks as the pregnancy.
NOTE: Fundal height can be measured over your underwear so you should not need to take yours off to have it done. If you want, you can feel your own symphysis pubis bone by placing your hands on the top of your hipbones, then moving them forward and down, following the curve of the hipbones down and across, to just below your pubic hairline in the middle. It feels like a hard bump under the pubic hair.
More info about Fundal Height
|Using a measuring tape to determine fundal height during pregnancy was first introduced in the late 1970's. It gained popularity in the late 1980's and because it is simple and inexpensive, it has become widely used by many maternity caregivers, although not all caregivers use it. The main aims of measuring the fundal height during pregnancy are to possibly detect:|
Fundal height measurements were adopted because it was believed to be more accurate than just the caregiver feeling (or palpating) the woman's belly with their hands. Observational studies in the 1980's estimated that detection rates of very small babies by palpating were about 30 to 50% successful, but by doing fundal heights this may increase to about 56% to 86%.However, a small random study in 1990 found that fundal height measurements were about 28% accurate and abdominal palpation about 48%. More recently, a larger random study found that fundal height measurement were about 46 to 48% accurate, with abdominal palpation about 24 to 29% accurate.
At this stage there appears on balance to be some benefit in doing fundal height measurements. However, caregivers concede it is not always reliable and we don't really have any technique that is more than 50% accurate.Bearing this in mind it is important to view fundal heights as just a guide, with very limited ability in detecting unusually small or large babies. Even the popular use of ultrasound in recent years to estimate a baby's weight has been shown to be up to 10 to 15% out, or + / - 400 to 600 grams (1lb to 1lb 6oz) and cannot really be relied upon.