Ultrasounds During Pregnancy: How Many, When and Why?
The doctor or a skilled technician uses a plastic transducer to transmit high-frequency sound waves through your uterus during a pregnancy ultrasound. These sound waves return to a machine, where they are converted into pictures of your baby. Ultrasounds can help your doctor monitor your baby's development, discover anomalies, determine your due date, determine whether you're carrying multiples, reveal the position of your placenta, and confirm the sex of your baby.
Most pregnant women have ultrasounds as part of their prenatal medical treatment, and they also provide parents their first glances of their developing baby. Although these images make lovely mementos, most women only require a few scans, and medical guidelines say that ultrasounds during pregnancy should only be conducted when a valid medical reason exists. Diagnostic ultrasound techniques have not been shown to have any proven harmful consequences on the baby. However, using ultrasounds for non-medical purposes is discouraged because, while no biological consequences have been proven to be produced by scans, there is always the chance that some will be discovered in the future (American Congress of Obstetricians and Gynecologists).
2D ultrasounds are the safest radiological modality available to pregnant women, however they should be used in moderation as with everything else (Monica Mendiola, MD).
Ultrasounds required for healthy women
It turns out that most pregnant women only require a couple of ultrasounds. During pregnancy, most healthy women get two ultrasound scans. The first should take place in the first trimester to determine the due date, and the second should take place between 18 and 22 weeks to confirm proper anatomy and the baby's sex. Most women only require these ultrasounds if they are normal and mom's abdomen measures are in line with her pregnancy.
If there are any issues with these initial ultrasounds, or if the foetal size changes along the way, a repeat ultrasound is recommended. In addition, if the mother has a medical condition such as diabetes or hypertension, she will be subjected to further scans.
Reasons for having ultrasounds
Ultrasound is used by the doctor for a variety of purposes, including:
To confirm you're pregnant
To determine your baby's age and development. This will help your doctor figure out when you'll be due. In order to monitor your baby's heartbeat, muscle tone, mobility, and general growth.
To see if you're expecting twins, triplets, or more children (also called multiples)
Before giving birth, check to see if your baby is in the heads-first position.
To examine your ovaries and uterus will be examined.
Early Pregnancy Ultrasound (6-8 weeks)
When you're six to eight weeks pregnant, you may get your first ultrasound, often known as a baby sonogram. However, not every woman will have this scan; some doctors may only perform it if a woman has specific high-risk pregnancy symptoms, such as bleeding, abdominal discomfort, or a history of birth abnormalities or miscarriage.
An early pregnancy ultrasound may be performed transgvaginally to allow specialists to see your baby more clearly. Your gynecologist will insert a tiny wand-like transducer probe into your vaginal canal, which transmits high-frequency sound waves into your uterus in this scenario. The sound waves reverberate off the foetus, sending information to a computer that converts the reflections into a black-and-white picture of your baby.
The baby's heartbeat may be seen at six weeks of pregnancy. Your doctor will also estimate your baby's due date, keep track of milestones, asses the number of babies in your womb, and check for an ectopic pregnancy.
Dating Ultrasound (10-13 weeks)
Those who skip the six-to-eight-week ultrasound may get a "dating ultrasound" between 10-13 weeks. The due date, your baby's "crown-rump length" (measured from head to bottom), the number of babies in the womb, and the foetal heartbeat are all revealed.
Nuchal Translucency Ultrasound (14-20 weeks)
A nuchal translucency (NT) test may be performed between 14 and 20 weeks to look for Down syndrome, heart problems, or other chromosomal abnormalities. If your screening test indicated a possible problem, you're 35 or older, or you have a family history of certain birth abnormalities, you might consider getting this ultrasound done (Joanne Stone, MD).
During a nuchal translucency screening, the doctor will use an ultrasound to determine the thickness of the back of the baby's neck (a blood test will also be used to determine hormones and proteins). A thicker neck might suggest a higher chance of birth abnormalities such as Down syndrome and trisomy 18.
Anatomy Scan (18-20 weeks)
This thorough prenatal ultrasound, which usually takes place between weeks 18 and 20 of the second trimester, lasts 20 to 45 minutes for a single baby and longer for multiples. It's the most comprehensive examination your baby will receive before birth (Jane Chueh, MD).
The doctor will monitor your baby's heart rate and search for abnormalities in their brain, heart, kidneys, and liver during the anatomy scan. Your baby's fingers and toes will be counted, birth abnormalities will be checked, the placenta will be examined, and the amniotic fluid level will be measured.
Third Trimester Ultrasound
In the third trimester, many expecting parents do not require an ultrasound. However, if your pregnancy is deemed high-risk—for example, if you have high blood pressure, bleeding, low levels of amniotic fluid, preterm contractions, or are over 35 years old—your doctor may do low-resolution ultrasounds in the office during your prenatal appointments for reassurance. If your cervix was covered by the placenta at your 20-week scan, you'll receive a follow-up ultrasound (Dr. Jane Chueh).
Doppler Ultrasound
A regular ultrasound uses sound waves to produce images; this ultrasound uses high-frequency sound waves to bounce off circulating red blood cells to measure blood flow and blood pressure. The test will evaluate whether or not your baby is receiving adequate blood.
Other Pregnancy Ultrasounds
Other pregnancy tests that need ultrasounds may be performed by the doctor. Chorionic villus sampling (CVS) or amniocentesis are two examples. Ultrasound is also used in foetal echocardiograms, which display the baby's heart beat and diagnose problems.
If your baby is at risk of birth abnormalities or is very under or overweight by the time you reach term, you may require further ultrasounds. The following factors can put your baby at risk:
If you smoke or consume alcohol while pregnant, or if you have a family history of birth problems, your baby's chances of developing birth defects are increased.
If you have asthma, inadequate weight gain throughout pregnancy, or have high blood pressure, your baby is more likely to be underweight.
If you're overweight or develop gestational diabetes while pregnant, your baby's chance of becoming overweight when he or she is born increases.
How many Ultrasounds during pregnancy are safe?
When used for medical purposes, an ultrasound is deemed safe for both you and the baby. Ultrasounds do not require radiation, but they should only be performed by a qualified expert who can accurately interpret the data. Some medical practises now provide 3D (high-resolution, realistic) and 4D (moving picture) ultrasounds, which may aid doctors in detecting prenatal anomalies and birth problems. Although ultrasounds are considered safe in medical settings, they may cause tissue heating or the formation of bubbles (cavitation). When ultrasounds are used outside of a medical requirement with untrained personnel, experts are unsure about the long-term repercussions of heated tissues or cavitation. As a result, ultrasound scans should only be conducted when a medical necessity exists, based on a prescription, and by suitably qualified operators (FDA).
It's crucial to remember that these are medical procedures that are performed to guarantee a healthy pregnancy and a safe birth. As a result, ultrasounds should only be used for medical purposes and only when a doctor has recommended them. While most women may expect at least two ultrasounds during their pregnancy, particularly the first and second trimesters, there are a variety of reasons why your doctor may recommend more. Ultrasound tests are crucial for monitoring your baby's growth, and it's natural to be concerned about the possibility of further screenings beyond routine visits.
Sources:
https://www.parents.com/pregnancy/stages/ultrasound/ultrasound-a-trimester-by-trimester-guide/
https://www.marchofdimes.org/pregnancy/ultrasound-during-pregnancy.aspx#
https://www.insider.com/how-many-ultrasounds-during-pregnancy
https://www.verywellfamily.com/the-types-and-timing-of-ultrasounds-during-pregnancy-5069852