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How to Measure Fundal Height and Fetus Size: Explained

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How to Measure Fundal Height

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As and when you progress in your pregnancy, you might often find yourself comparing the fetal growth from the top of the uterus via the abdomen to the size of a vegetable or fruit, as per the week size in the pregnancy app or through Parenthood bliss’s website. However, the doctor would help you with more accuracy to help ensure that the pregnancy is going as expected.

We understand that the progress might leave you curious as to how the doctor measures the fundal height and size all throughout your pregnancy. More importantly, what importance does it have to keep a check on the height measurement? If so, you have landed on the right article, as we are here to help you find answers to all these questions. Read on to discover!

What is Fundal Height?

Fundal height is a measurement used during pregnancy to estimate the size of the uterus. Specifically, it is the distance from the pubic bone to the uterus’ top, measured in centimeters. This measurement is typically taken with a tape measure from the pubic bone to the highest point of the uterus, known as the fundus. The fundus is the rounded upper portion of the uterus.

Fundal height measurements are commonly used by healthcare providers as a quick and non-invasive way to assess fetal growth and gestational age during prenatal care. The general idea is that as a pregnancy progresses, the fundal height in centimeters should roughly correspond to the number of weeks of gestation.

It’s important to note that fundal height measurements have some limitations. Factors such as the position of the baby, the amount of amniotic fluid, and the mother’s body mass index (BMI) can all influence the accuracy of the measurement. Additionally, individual variations are common, so healthcare providers use fundal height as one of several tools to monitor the health and development of the fetus.

If there are concerns about fetal growth or development, healthcare providers may use additional methods, such as ultrasound, to gather more detailed information. Pregnant individuals should always follow the guidance of their healthcare provider for personalized care and advice.

How to Make an Accurate Fundal Height Measurement?

Fundal height measurements are done in centimeters from the pubic bone to the top of the uterus. This helps estimate the length and weight of the baby that the doctor then compares to the expected average fundal height to the average fundal height as per the week of the trimester.

However, as measuring the exterior of the uterus isn’t a precise science, it’s okay if the fundal height doesn’t match or measure up with the estimated due date.

When And How Do Doctors Measure The Fundal Height By Week In Utero At The Gestational Age?

The simplest way followed by the doctors to measure the baby’s size in the utero is by measuring the expecting mom’s fundal height, which means, the distance between the pubic bone to the top of your uterus in centimeters (Symphysis fundal height). You may also expect the doctor to palpate the abdomen to get an idea about the baby’s size.

For instance, post 24 weeks in the pregnancy, the fundal height in centimeters would be roughly equivalent to the week of gestation. Like, if 29 weeks pregnant, the fundal height would probably be 29 in centimeters.

However, the measurement of the fundal height starts to decrease between weeks 37 and 40, as the baby begins to descend into your pelvis, preparing for birth.

On the other hand, transvaginal and transabdominal ultrasounds are the other ways to measure the fundal height more accurately. In this ultrasound, a wand sends sound waves that in turn bounce off of the baby, producing an image you see on screen. Here, a sonographer will take the measurements used to estimate the baby’s weight via a computerized algorithm.

You might wonder, when does a practitioner start measuring the baby? The measurement starts around 20 weeks of pregnancy and in every prenatal appointment until the birth of your little one.

In the first trimester, the use of ultrasound is to estimate the due date via the measurement from the baby’s crown-to-rump length, or from the top of the head to the bottom. Otherwise, by the third trimester, the ultrasound helps measure the parts of the baby, size, and weight, ensuring a healthy pregnancy as expected.

Note – Ultrasounds are usually accurate, plus or minus 2 centimeters over-or under by 10 to 20 percent in rare cases that lead to unnecessary interventions like C-sections. Also, make sure you do not indulge in unnecessary ultrasounds irrespective of how safe they might be.

How Accurate Is The Fundal Height By Week? Is It Relatively Small For The Gestational Age?

Mostly no! Estimating the fundal height in utero is the best and simplest way to know the baby’s size based on averages. Measuring larger than expected or smaller than the average is completely normal as the body mass index of the expecting moms varies.

The fundal height measurements in non-obese women are often off by two weeks. There’s always a margin of error when the doctors match the number while estimating the exact weight and size of the baby. They could be off by a pound or even more, and a centimeter or two bigger or smaller.

This inaccuracy in measuring the fundal height could be less accurate, including the position and volume of the amniotic fluid, by a week or two in women who are obese or have a history of uterine fibroids. It doesn’t always mean intrauterine growth.

Fundal Height Measurement: What To Expect If The Doctor Measures It To Be Either Big Or Small?

Surely, getting results of the baby’s fundal size to be relatively similar to the gestational age helps to ensure that the pregnancy is on track and as expected. However, if there is a difference in the fundal height of more than three weeks during your trimester, the doctor will for sure look into it.

Mostly, in these readings, the cases turn out to be harmless as the due dates are wrongly estimated. Healthcare practitioners usually estimate the due date from the first day of the last menstrual period, but there are chances that the conception took place earlier or later.

Also, the results that turn out to be larger or smaller than expected could indicate other conditions too. For instance, small measurements could mean that there isn’t much amniotic fluid or intrauterine growth restriction.

On the other hand, larger measurements may be a sign of way too much amniotic fluid, uncontrolled gestational diabetes, or a uterine fibroid. If either is suspected, there could be an extra ultrasound or the pregnancy will be monitored closely to prevent any foreseen dangers to either you or the baby.  

That’s all about fetal fundal height and ways to measure it. However, while we speak of the growth of the baby, you might want to keep track of the fetal movement and kick counts in your trimester for a better understanding of the baby’s health.

To Conclude:

The benefit of measuring the size of the baby in utero helps with a rough estimate and understanding of the pregnancy. However, these measurements aren’t quite accurate and could in a few cases be two or three weeks off, but work as a guide to the care you receive. Also, visiting the doctor during all prenatal appointments helps in a healthy pregnancy and delivery.

FAQs: How to Measure Fundal Height and Fetus Size

1. What is fundal height in pregnancy?

Fundal height is calculated by measuring the distance between the top of the uterus and the pubic bone. The doctor usually palpates the abdomen to estimate the baby's size. This correlates with the fundal height to the expected week of gestation, i.e., by the 24th week of pregnancy.

2. How is the fundal height measured?

These fundal heights are measured by the doctor via ultrasound while you lay flat on your back. The height is measured in centimeters. Or, the doctor would make use of a measuring tape to see the distance from your pelvis to the top of the uterus.

3. Why is fundal height important?

Your doctor can record your fundal height over time to ensure that you're gaining the right amount of weight and your baby is growing healthily. Because your growing baby is what's causing that belly bump, fundal height can help demonstrate how big your baby is (fetal growth).


Reviewed By:

Esha Chainani - Obstetrician and Gynaecologist

Esha Chainani - Obstetrician and Gynaecologist

Dr. Esha Chainani is an Obstetrician, Gynaecologist, and laparoscopic surgeon who aims to break the stigma around women’s health by advocating an inclusive and open practice of obstetrics and gynecology and an author of several internationally published research papers and health articles in the media like the Swaddle.
She also founded Premaa, a non-profit to reduce maternal morbidity and eventual maternal mortality by providing lower-income pregnant women living in urban areas with cell phone access through an app that can feature an entire section about contraception as well for a whole gamut of reproductive health.
A panel for multiple health sessions including with the UN, USAID, BMC, gender at work, and multiple non-profit organisations, and is on the advisory panel of the South Indian medical students association.

On behalf of the editorial team at Parenthoodbliss, we follow strict reporting guidelines and only use credible sources, along with peer-reviewed studies, academic research institutions, and highly respected health organizations. To learn about how we maintain content accurate and up-to-date by reading our medical review and editorial policy.

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