First trimester ultrasound: pregnancy viability and chromosomal abnormalities
Before discussing the first-trimester ultrasound and its objectives, it's helpful to understand what an ultrasound is . This method uses the ability of sound waves to pass through tissues and bounce off them depending on their density. The ultrasound machine converts these sound waves, or echoes, into an image that allows the specialist to make a diagnosis.
These ultrasounds are completely harmless and will not harm the expectant mother or the fetus in any way. They lack the ionizing effect of X-rays.
How an ultrasound is performed and types
There are two types of ultrasounds:
- By abdominal route: It is rarely performed during the first trimester, but is always used in the second and third trimesters. To do this, the woman lies on her back and a gel that facilitates ultrasound transmission is spread over her abdomen. A transmitter head is responsible for acquiring and transmitting the images to a screen.
It is recommended to come to the appointment with a full bladder to improve image quality.
- Vaginally: It is most suitable during the first trimester of pregnancy. To perform it, the woman places herself in the gynecological position and a probe protected by a gel-covered latex sheath is inserted into the vagina.
It requires no preparation and is more effective if the woman has an empty bladder.
First trimester ultrasound
First-trimester ultrasound is becoming increasingly important. New equipment allows for the early and accurate diagnosis of potential abnormalities. The preferred approach is transvaginal ultrasound , although it can sometimes be supplemented with abdominal ultrasound.
First trimester ultrasound objectives
Now that we've analyzed what an ultrasound consists of, and more specifically, a first-trimester ultrasound, let's review its specific objectives:
First, although they only represent 1% of cases, ectopic pregnancy is ruled out . These types of pregnancies outside the uterus are not viable.
The first-trimester ultrasound also allows for the determination of gestational age by measuring the embryo's length from crown to rump. The measurement used to establish this data is the crown- rump length (CRL ).
The embryo's viability will also be examined, assessing the heart rate with a vaginal ultrasound from the sixth week or abdominally from the seventh week of gestation.
It will also be possible to detect multiple pregnancies and whether or not the embryos share a placenta or amniotic sac.
Likewise, the normality of the woman's internal genital system - uterus and ovaries - will be verified.
Finally, signs of chromosomal abnormalities can be detected through ultrasound screening . This technique studies, among other variables, the nuchal translucency or fold of the fetus . That is, it analyzes the fluid that all embryos have behind the neck. If its thickness exceeds 3 mm, it is considered abnormal, as is the presence or absence of the nasal bone . These findings will require us to perform other diagnostic tests, such as chorionic villus sampling (CVS) or amniocentesis, to rule out chromosomal abnormalities. Of these abnormalities, the most common is Down syndrome.
In addition to ultrasound data, maternal age and biochemical markers will be assessed - pregnancy-associated plasma protein A (PAPP-A) and free β-HCG , which are hormones associated with placental function - obtained through blood tests.
- In This Video published on the Instagram account of the Women's Unit of the Ruber International HospitalDrs. Isabel Rodríguez-Piñero and Sara Rubio offer us some very interesting information about first-trimester ultrasounds.
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- Foods and habits not recommended and allowed during pregnancy
- Nutrition for pregnant women: optimal fetal development and disease prevention
We also recommend watching a video in which Dr. Lorenzo explains the various checkups that should be performed during pregnancy to detect any pathologies early that could complicate the pregnancy or lead to unwanted miscarriages. You can find the video here.
If you found this article interesting and would like to be seen by a specialist in Gynecology and Obstetrics, the Women's Unit at Ruber International Hospital has a specialized department in this area. You can request more information by calling 91 387 51 72/73/74 or schedule an in-person appointment with top specialists.