First Trimester: Class Notes

Vocabulary flashcards covering key terms and definitions from the first trimester class notes.

Conceptus stage

Up to 5 weeks of pregnancy.

Embryonic stage

The period of development from 6 to 10 weeks.

Fetal stage

The stage of development from 9 weeks to beyond 38 weeks.

1st trimester

The period from 1 to 12 weeks of pregnancy.

2nd trimester

The period from 13 to 28 weeks of pregnancy.

3rd trimester

The period from 29 to 38 weeks of pregnancy.

Gestational Sac (GS) size criteria

GS 2-3mm correlates with 4 weeks, GS 5mm ~5 weeks (should be visualized on sonogram).

Small sac size delay

Difference of MSD and CRL <5mm correlates with risk.

PAPP-A

Preg-associated plasma protein, decreased levels can be indicative of Down syndrome.

Cardiac activity in embryo

Should be visible by 7mm CRL and MSD 25mm, always by 9mm CRL.

Visualization of the yolk sac (YS)

Max size is 5-6mm at 10 weeks; important for evaluation.

Amnion

A membrane that forms a sac around the embryo; an enlarged amnion relative to CRL can indicate issues.

Fetal pole growth

Should correlate with amnion growth; discrepancies point to negative outcomes.

Bradycardia

Abnormally slow heart rate; <100 BPM before 6.2 weeks.

hCG levels for IUP confirmation

Threshold for evaluating an IUP is 1000-2000 mIU/ml (new criteria 3000-4000 mIU/ml).

Placenta visualization

Can be seen as early as 6-7 weeks but reliably seen at 10-12 weeks.

Recurrent miscarriages criteria

Defined as 3 or more consecutive first trimester losses.

Teratogens

Environmental agents responsible for fetal anomalies.

Hematoma

Intrauterine blood collection, often associated with failed pregnancies.

Blighted ovum

Gestational sac without an embryo.

Differentials for no embryo/YS

Includes normal early IUP, abnormal IUP, positive hCG with unknown location, and pseudogestational sac.

Chorionic bump

Irregular convex bulge on the chorionic surface that may mimic a non-viable embryo.

Anencephaly

Severe fetal condition where the skull does not develop properly.

Encephalocele

Protrusion of brain tissue through a defect in the skull.

Holoprosencephaly

Failure of cleavage of the forebrain, causing developmental issues.

Omphalocele

Abdominal wall defect where organs are contained in a peritoneal membrane.

Gastroschisis

Abdominal wall defect where bowel loops are not contained by a membrane.

Cystic hygroma

Accumulation of lymphatic fluid leading to large cystic spaces, associated with chromosomal abnormalities.

Amniotic Band Syndrome

Condition involving entanglement of fetal extremities leading to deformities.

Rhombencephalon

Structure developing in the embryonic brain during 7-9 weeks of pregnancy.

Physiological bowel rotation

Normal rotation of the bowel occurring around the 8th week of pregnancy.

Mean sac diameter (MSD)

Calculated as the average of length, height, and width of the gestational sac.

Nuchal translucency (NT)

Measurement taken between 11-14 weeks to assess risks for chromosomal abnormalities.

Cervical measurement

If cervix is <3cm, transvaginal ultrasound is needed to evaluate cervical insufficiency.

BPD (Biparietal Diameter)

Sonographic measurement of the fetal head used to assess gestational age.

AFI (Amniotic Fluid Index)

Measure of amniotic fluid volume used to assess fetal health.

Fetal age

Also known as conceptual age, refers to the age of the embryo or fetus calculated from conception.

Maternal blood screening tests

Tests such as triple screen, quad screen, and NIPT used to assess potential for fetal anomalies.

Triple screen test

A blood test for AFP, hCG, and estriol to assess risk for chromosomal abnormalities.

Quad screen test

A blood test adding inhibin-A to the triple screen components for improved sensitivity.

Non-invasive prenatal testing (NIPT)

Blood test looking for fetal DNA, offered primarily to women over 35 or with a high-risk result from other screenings.

Sono markers for T21 (Down syndrome)

Include nuchal fold thickening, absent nasal bone, and echogenic bowel.