Feeling your abdomen
Feeling the pregnant belly is part of every antenatal visit after 12 weeks of pregnancy. The medical term for this is “abdominal palpation”. The aim of it is to monitor the growth and position of your baby. It does not hurt the baby.
From 12 to 20 weeks
The main aim of abdominal palpation is just to ensure that the uterus is growing.
- At 16 weeks of pregnancy the top of the uterus is halfway between the pubic hair line and the belly button
- At 20 weeks of pregnancy the fundus should be close to the level of the belly button.
- Measuring your fundal height is not essential at this stage.
From 20 to 34 weeks
The baby is big enough to feel where the head is. Unborn babies change position frequently during this phase of pregnancy and are quite often in a breech position (bottom down) or lying across your belly in a transverse position.
The size of your uterus should be approximately relevant to how far pregnant you are. Many caregivers use fundal height measurements as part of monitoring the baby’s growth during this phase of pregnancy.
From 34 to 37 weeks
The baby is more than likely in a head down position. Your caregiver feels for your baby’s head and perhaps detects which side of your belly their back is laying on (right or left).
Babies at this stage do not usually move their head from being down now because their head is much larger and heavier, but their back can move frequently from one side of your belly to the other.
The uterus reaches the base of your breast bone or sternum by about 36 to 37 weeks. The fundal height measurements become irrelevant after 35 to 36 weeks.
From 37 weeks to birth
Your baby should definitely be head down now.
Your caregiver feels your baby’s head and tries to determine if it has engaged yet. The baby’s head can engage anytime from 1 to 4 weeks before the birth. Although it is normal for some women’s babies not to engage until they start labouring, especially if it is a second or subsequent baby.
If your baby’s head engages, the fundal height usually drops lower, although fundal measurements are not generally used during the final weeks of pregnancy.
Measuring fundal height
Studies have shown some benefit in doing fundal height (FH) 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 ultrasound in estimation of baby’s weight has been shown to be up to 10 to 15% out, or ± 400 to 600 grams.
Measuring FH involves the woman lying down (it is not meant to be donein a standing or sitting position) and her caregiver placing the end of the measuring tape on her pubic bone. The symphysis pubis bone is situated just below the pubic hair line. 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 (cm).
Fundal heights tend to be used from 24 to 37 weeks of pregnancy. A text book fundal height is supposed to equal the same amount of weeks as the pregnancy. For example, 24 weeks pregnant equal 24 cm and so forth (up until about 36 to 37 weeks).
However, fundal height measurements can fluctuate 2 to 4 cm higher or lower than the expected norm. Most caregivers are reasonably happy if your measurement is consistently lower or higher at each visit (for example 22 cm at 24 weeks and then 26 cm at 28 weeks). However, they may be concerned if you measured at 24cm at 24 weeks and only 25cm at 28 weeks, because the baby has not demonstrated much of a progressive growth over the four weeks.
Listening to your baby
An unborn baby’s heart rate changes as they grow:
- At 8-10 weeks, the rate is high at around 170 to 200 beats per minute (bpm).
- At 20 weeks, the rate drops to be more around 120 to 160 bpm.
An unborn baby’s heart beat can sound a little like a horse galloping.
A hand held Doppler machine can detect baby’s heart beat from about 12 to 14 weeks of pregnancy, although this is not always possible. It is definitely detectable from about 16 to 18 weeks of pregnancy.
Ultrasounds can detect baby’s heart beat from around 7 to 8 weeks of pregnancy (possibly as early as 6 weeks in some cases).
Essentially, the head of the Doppler machine is placed on the woman’s belly with conducting gel (similar to gel used in regular ultrasounds), which helps the machine pick up the baby’s heart beat. The machine is then switched on and the caregiver tries to angle it in the best possible way to detect the baby’s heart beat. This may require a little bit of pressure as they gently push the Doppler into your belly. It may take a minute or so to find your baby’s heart beat, especially if the pregnancy is very early (less than 18 weeks) or your baby is lying in an awkward position or is very active.
You may also hear other noises through the machine:
- A slow swoosh pulsating (blood pulsating through the arteries in your uterus)
- A fast, soft pulsing sound at about the same rate as the baby’s heart beat (blood flowing through the baby’s umbilical cord)
- Sporadic thuds (the baby kicking!)
If there is any concern, a continuous monitoring with CTG machine for 20 minutes or more is indicated.
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