1st trimester ultrasonographic screening

Baby Shelly offers the first ultrasound screening, which  takes place between 11+0 and 13+6 (week+day) during pregnancy. Age of gestation from the first day of the last menstrual cycle is recorded. In the case of an unknown date or abnormal cycle of a menstrual period, the dating of conception is determined based on ultrasonographic estimation of the length of the foetus from the top of the head (crown) up to the bottom of the buttocks (rump), Crown Rump length The gestational age is not established (CRL). The ultrasound measurements take place between CRL values of 45 and 84 mm at 11+0 weeks and around 84 mm at 13 + 6 weeks.

3D ultrasound scanning is also called first quarter screening during this pregnancy. The word is expected to run for an average of 40 weeks, 10 lunar months (1 lunar month = 4 weeks) or around 9 calendar months. The pregnancy cycle is subsequently split into three or "trimesters" The term "trimester" which is derived from Latin, is simply translated "three months" and hence the first cycle can only last until the end of the 12th week if we are observing lunar months (3x4 weeks). In this scenario, scanning for the first quarter will be a little misleading because we are speaking about the time span up to 13+6 weeks in reality.

Typically, the term screening involves looking for a disorder or demographic abnormality while using multiple exams. Screening of certain structural flaws by foetuses with elevated risk of chromosome deficiencies such as Down syndrome (trissomy 21), Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), and others in the first trimester. These defects are classified as markers of small or significant structural and hemodynamic changes. The ultrasound scanning is combined with biochemical screening in order to improve the rate of identification of chromosome abnormalities.

A biochemical screening is conducted to establish amounts of certain glycoproteins or hormones in maternal blood (PAPP-A, β-hCG free β-subsunit, alpha-fetoprotein-AFP, unconjugated estriolet). Anomalies in foetal anomalies can increase their risk.

In the first 10+0 and 12+0 weeks biochemical sampling (PAPP-A, β-hCG) is completed. Each woman has a certain history (or possibility of a chromosome malfunction in her fetus/baby) (Down syndrome, Edwards syndrome, etc.). The risk is balanced by the above risk by multiplying the a priori risk by a set of chance ratios which are dependent on the outcome of biochemical or ultrasound tests and depending upon the period of their gestation and the duration of their gestation (combined test).

Significant volumes of details are provided by an ultrasound test from 11+0 to 13+6 weeks of pregnancy. A foetus may display some signs (markers) of chromosome defects in this pregnancy period (Down syndrome and Edwards syndrome) and other (morphological) structural abnormalities (gastroschisis, omphalocele, pentalogy of Cantrell, limb defects, anencephaly, and others). Especially if many causes are reduced (sizes of observed structures, placenta and foetal location, maternal obesity, etc), such heart defects may even be diagnosed in good echo conditions at this gestation stage.