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Fundal height, which is clinically referred to as Symphysio-Fundal Height (SFH) is a measurement taken in pregnant women after crossing 24 weeks of pregnancy. It is the distance between a prominence on your pubic bone and the top of the palpable uterus. It can be used as a measure of gestational age and to estimate foetal growth. Gestational age is the measure of the age of the pregnancy, that is, how far along you are in your pregnancy.
Sometimes, there can be a discrepancy in calculating the gestational age due to irregular dates of your last period. Sometimes, the foetus may have some developmental issues resulting in decreased growth, which can be picked up by an SFH measurement not corresponding to the known gestational age. This can direct your doctor to order further tests to look for any possible problems with the pregnancy.
The calculator can be used to calculate the following three parameters.
SFH percentile compares the media fundal height with your actual fundal height to get a percentile.
SFH to gestational age estimates the gestational age as per the measured fundal height.
SFH to foetal weight calculates the baby's weight according to fundal height.
The uterus is the organ that houses the developing foetus. It is present inside the pelvis in a non-pregnant woman. During pregnancy, the uterus has the capability to expand with the growing foetus. Once the pregnancy crosses 24 weeks, a normal foetus is big enough that the uterus longitudinally protrudes into the abdominal cavity, and can now be felt by palpating the abdomen.
Once this occurs, Symphysio-Fundal Height can be measured as follows.
The pregnant person is asked to lie down flat on a table.
The symphysis pubis is palpated. This is a prominence on the pelvis. It refers to the point where the two pelvic bones are joined at the top centrally by cartilage.
The fundus of the uterus is palpated. The fundus is the uppermost part of the uterus that can be felt in the abdomen. Normally, the foetus' legs occupy this region. When the head is present at the fundus, it is termed a breech pregnancy. Sometimes the baby can lie diagonally (oblique lie) or horizontally (transverse lie).
Using a tape measure, the distance between the symphysis pubis and the fundus is measured.
Once your pregnancy reaches 24 weeks, the fundal height measured corresponds to the number of weeks of your pregnancy (gestational age), plus/minus 2. For example, if you are in your 29th week, the expected fundal height is 29 cm +/- 2 cm.
The position of the fundus gradually changes and keeps going up the abdomen as the pregnancy progresses. By 26 weeks, the fundus is usually by the belly button. By 36 weeks, the fundus reaches the breast bone (so, the fundal height will be around 36 cm).
Following this, there will be a drop in the fundus and a decrease in the fundal height. As the baby gets close to being born, it slowly starts descending and occupying the lower areas of the pelvis. The part of the baby over the vagina will enter the pelvis as it makes its way out. This is called engagement, typically of the head, which can cause the fundal position to lower and a consequent decrease in the fundal height.
Fundal height is one of the easiest, simplest, and completely non-invasive methods of monitoring the progress of pregnancy and the health of the developing foetus. It does not cost any extra money and can be performed easily.
It is very important as mostly it is the first sign of picking up any problems with the developing baby. When the fundal height is less than the gestational age by more than 3, it means that there's a possibility that the baby is not the expected size it should be for its age. This can prompt your doctor to perform an ultrasound scan which offers a much more comprehensive look at the foetus and state of pregnancy.
There is a margin for error, but this measurement has been an extremely useful tool in clinical practice. Typically, once you cross 24 weeks, your fundal height is measured at every visit. In addition, your doctor will look for the baby's heartbeat with a handheld Doppler probe. They will also palpate your uterus abdominally to look at its contour, check which direction the baby is lying in, and check for other abnormalities.
Your Symphysio-Fundal Height can be less in comparison to your gestational age in the following conditions.
Foetal Growth Restriction: A spectrum of conditions can cause the foetus to not grow appropriately, resulting in a small-for-gestational age baby. It is also called IUGR (intrauterine growth restriction). The causes can range between poor maternal nutrition, anaemia, infections, genetic abnormalities, etc.
Reduced amniotic fluid: The uterus is filled with amniotic fluid or liquor amnii which is essential for the baby to develop. When it is reduced, the condition is called Oligohydramnios. It can result in the uterus being smaller than it should be.
Short/petite mother.
Towards the end of pregnancy due to engagement of the head or whichever part of the foetus is below into the pelvis.
Symphysio-Fundal Height can also be more than your expected gestational age. This is seen in the following scenarios.
Wrong calculation of dates: Calculating the due date and gestational age can be a challenge in women who do not have regular periods/remember the date of the start of their last pregnancy. This can sometimes result in a wrong calculation. This can be rectified by making sure an ultrasound scan is done at the time of confirmation of pregnancy, also known as a dating scan, which uses many parameters to determine an accurate due date and gestational age.
Excess amniotic fluid: This condition is called polyhydramnios. This can occur simultaneously with a big baby in a condition called foetal macrosomia, where the foetus is bigger than the expected weight for its age. This is commonly seen in diabetic mothers.
In a twin pregnancy.
In obese mothers, it can be difficult to pinpoint the fundal position by palpating the abdomen, and hence a proper measurement may not be performed.
If the pregnancy is in mothers with uterine fibroids.
When the baby is in breech position, that is, the head is at the top and the feet are below.
There are several reasons for fundal height not corresponding with gestational age. It is best to consult a gynaecologist (OBGYN) to carry out the relevant tests and give the necessary treatment.
Small-for-gestational-age babies need to be treated as per the underlying cause. This could be a medical condition in the mother, substance abuse, genetic disorders, etc. The doctor can assess the treatment plan accordingly.
Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.