Introduction:
The first three months or the first 13th week of pregnancy is known as the first trimester. This period is known as the formative period for several fetal organs. Any abnormality during this period can be fatal. Diagnosing any abnormal condition during this period is essential for the prediction of pregnancy outcomes.
What Is First Trimester Ultrasound?
First-trimester ultrasound scan is one of the most commonly used diagnostic procedures. This is done between the 12th to 14th week of the pregnancy period. This scan is also known as a level I scan. This type of scan is done either through a transabdominal route or a transvaginal route. Various parameters are checked during this scan.
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Assessment of Fetal Age: Accurate assessment of the fetus is done through ultrasound. For this purpose, different measurements like head circumference (HC), biparietal diameter (BPD; the diameter of the fetal skull), and crown–rump length (CRL; length of the embryo from the top of the head to the bottom of the torso) are measured. The assessment of the fetal head is necessary for follow-up procedures and measuring fetal growth.
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Identification of Anatomical Structures: Identification of several anatomical factors is an essential part of the growth assessment of the upcoming baby. The ossification process of cranial bones can be visible after the 11th week of pregnancy. In the brain, appearance of the hemispheres and ventricles can also be seen. The formation of choroid plexuses (a typical formation of the blood vessels in the brain) can also be observed during this stage. The development of the spinal cord and vertebrae can also be identified using the ultrasound method. In the thoracic cavity, heart and lung contains can be visible during this period. But Doppler assessment is not recommended in this period. Bony presence in the limbs and insertion of the umbilical cord is accessed.
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Detection of Chromosomal Abnormality: Nuchal translucency is a method to measure chromosomal abnormalities. In this method, the collection of fluid under the skin fold is measured. The ideal measurement should not be more than three millimeters. Increased thickness of the nuchal translucency is suggestive of structural or chromosomal abnormalities. Down syndrome (presence of an extra copy of 21 chromosomes) and Edwards' syndrome (presence of an extra copy of the 18th chromosome) is associated with increased nuchal translucency.
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Detection of Status of Pregnancy: Different complications regarding pregnancy status can be evaluated during this period. Ectopic pregnancy is a complication that is seen in around six percent of pregnant women. In this condition, the growth and implantation of the fertilized egg occur outside the uterus. In the ultrasound evaluation empty uterine cavity, decidual cast, and a thickened echogenic endometrium can be seen. Another complication that can be visualized through ultrasound is subchorionic hematoma in intrauterine pregnancy. It is the collection of blood between the uterus and the embryo. This is seen as an avascular collection in between the gestational sac and decidua basalis (the portion where the placenta is formed). Serious pregnancy complications like spontaneous abortion and incomplete abortion can be confirmed using ultrasound. In these cases, slight protrusion of the uterus and the presence of uterine contents can be observed in ultrasound examination. In all these cases, patients usually come with the symptoms of vaginal bleeding or pain in the lower abdomen. Another pregnancy anomaly that can be observed in ultrasound is a molar pregnancy. In this condition, a tumor is developed inside the uterus during pregnancy. This is formed by the abnormal proliferation of trophoblasts. In a transvaginal ultrasound, the molar pregnancy looks like a solid mass with the presence of a fluid-filled sac.
What Are the Different Laboratory Tests?
Different laboratory tests are done for the assessment of various medical parameters.
1) Diagnosis of Infectious Disorders:
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HIV is the most common disorder which needs to be ruled out during pregnancy. Acquired immunodeficiency syndrome (AIDS) is caused by the HIV virus. This causes severe immunodeficiency and is responsible for several pregnancy-related complications like stillbirth, preterm delivery, and low birth weight. Also, HIV is associated with vertical transmission of the virus to the neonate. In case of a positive HIV test, an anti-retroviral drug is started and analysis of viral load is accessed.
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Syphilis is another sexually transmitted infection that is responsible for pregnancy complications. Also, it may transmit to the body of the newborn and is responsible for congenital syphilis. A serological test of the mother is done for detecting syphilis.
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Gonorrhea is another sexually transmitted infection that may cause eye disorders in the newborn baby. Assessment of the vaginal sample is done to detect the presence of gonorrhea.
2) Assessment of Systemic Disorder:
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Assessment of blood sugar is one of the routinely done procedures. Diabetes is often associated with several medical complications. Also, in some cases, patients develop high blood sugar during pregnancy which is known as gestational diabetes. For this purpose blood glucose level measurement is essential.
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Other hormonal disorders like hypothyroidism, and hyperthyroidism may also impact pregnancy outcomes. That is why measurement of thyroid level is essential.
3) Chorionic Villus Sampling (CVS): This diagnostic test is done for the detection of chromosomal abnormalities. This test is done between the 11th to 14th week of pregnancy. Sample from the placenta is collected either through the transvaginal or transcervical route.
4) Cell-Free DNA Testing/Non-Invasive Prenatal Screening (NIPS): In this test small fragments of the fetal DNA circulating in the mother's blood are collected. These DNS are free floating and are known as cell-free DNA. Several conditions like Down syndrome (trisomy 21, extra copy of chromosome 21), trisomy 18 (presence of an extra copy of chromosome 18), and trisomy 13 (present extra copy of chromosome 13) can be detected through this method.
5) Detection of plasma protein A (PAPP-A) and beta-human chorionic gonadotropin is essential to access pregnancy outcomes. Low levels of plasma protein A (PAPP-A) and beta-human chorionic gonadotropin is associated with early pregnancy loss and fetal growth restrictions.
Conclusion:
Maternal or fetal complications can be harmful to pregnancy. The role of prenatal diagnostic procedures in the first trimester is to predict pregnancy complications. These procedures help to determine treatment protocol and surgical procedure and can be proven to be life-saving.
