Flowmetry in pregnancy

A particular ultrasound technique is the flowmetry or Doppler scan which allows to evaluate the blood flow towards the uterus (maternal flowmetry) or between the placenta and the baby (fetal flowmetry).

The flowmetry of the uterine arteries (maternal flowmetry) is performed in particular between the 17th and 24th week of pregnancy  but can also be used in the first trimester in conjunction with prenatal diagnostic tests .

Umbilical artery flowmetry is usually performed from the 32nd week and often in conjunction with growth ultrasound . In this case it can also go to measure blood flow not only through the umbilical cord but also in other parts of the baby’s body, such as the brain and heart. This checks whether the fetus is getting all the oxygen and nutrients it needs through the placenta.

 When is flowmetry required?

Your doctor may request a Doppler if in particular:

  • it is a twin pregnancy
  • whether the woman has a high or low body mass index
  • if the woman has high blood pressure or diabetes
  • if the woman is a smoker, she takes alcohol or drugs
  • you are the child is not growing regularly (or there is a growth delay )
  • if the woman has had another pregnancy with fetal growth retardation
  • in case of perinatal death or late abortion in the previous pregnancy
  • if the woman has had an infection such as toxoplasmosis or cytomegalovirus .

Uterine artery flowmetry

The uterine arteries carry blood to the uterus, so a Doppler scan of the uterine arteries verifies that blood reaches the placenta.

The baby needs plenty of nutrients and oxygen to grow properly. Therefore, the walls of the uterine arteries should be elastic, to allow for proper blood flow. In pregnancy, these normally small arteries increase in size to allow for more flow.

If blood does not reach the placenta in optimal quantities, the baby may not get the nutrients and oxygen it needs through the umbilical cord.

A Doppler scan of the uterine artery is done if, for example, you have a high chance of developing pre-eclampsia , a condition that affects how the placenta works.

Umbilical artery flowmetry

This type of Doppler scan checks for blood flow through the umbilical cord from the baby to the placenta. This way you can see if the baby is getting everything it needs from the placenta.

If you’re having problems doing umbilical artery flowmetry, your doctor will also evaluate blood flow in your baby’s brain and in your aorta, which is your body’s main artery.

If problems are noticed, subsequent flow measurements may be required, every few days, to check the baby’s health and decide the best time and place to give birth.

If flowmetry shows that the baby is not getting enough nutrients or oxygen, it may be necessary to deliver early.

The cardiotocograph

The cardiotocograph (CTG), which is usually used during labor, is a form of Doppler that uses only sound and does not produce images. Allows you to check the rhythm of the baby’s heartbeat.

There are home Dopplers on the market that allow you to listen to the fetal heartbeat, but if you are experiencing an uncomplicated pregnancy it is not necessary to buy it. The important thing is to monitor the child’s movements throughout the day. If your child’s movements slow down or you notice changes from their usual movements, it is very important to call your doctor or go to the hospital for a check-up.

Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.

Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.

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