1st trimester Flashcards
some causes of uncertain LMP? (5)
- poor menstrual history
- amernorrhea
- prolonged or short cycle- not every 28 days
- DUB (dysfunctional uterine bleeding)
- recent miscarriage
Before the advent of pregnancy testing and sonography, what was the most identifiable reference point for the beginning of the pregnancy?
LMP
How many days is pregnancy?
- calendar
- lunar months
280 days from the first day of the LMP
- 9 calendar
- 10 lunar months
what is Nägele’s rule also known as?
- in clinical practice, the term gestational age is used interchangeably with menstrual age
why is the knowledge of an accurate gestational age needed?
to manage the pregnancy optimally
what are the two 1st trimester measurements? (4)
biometry:
- gestational sac (mean sac diameter)
- crown-rump length
additional measurements:
- yolk sac
- nuchal translucency
what is a normal yolk sac measurement?
2-6mm
what is the normal nuchal transluceny measurement?
<3.5mm between 11 and 14 weeks
what is the 1st sonographic evidence pf an intrauterine pregnancy?
gestational sac
gestational sac on u/s?
- anachoic fluid collection surrounded by an ecogenic ring in the fundal region of the endometrial cavity
what is the echogenic ring in the gestational sac representitive of?
- chorion and decidua capsularis
Absence of the echogenic ring should prompt what?
- suspicion of a pseudogestational sac associated with ectopic pregnancy
- this may warrant clinical correlation with beta-hCG levels
how to measure the gestational sac?
- with 2 scan planes
- measurement made in each of the 3 dimensions, of the gestational sac can be used to calculate a mean sac diameter (MSD)
- should be made at the interface between the echogenic border and the fluid
With high-frequency transvaginal technique, a pregnancy dating only 4 weeks and 1 or 2 days from the LMP may be visualized as what measurement?
- 2-3mm fluid collection within the uterus
the MSD should correlate closely with what?
suspected gestational age
Any significant variance or suspicion of pregnancy loss should be closely correlated with?
beta-hCG levels
Normal first-trimester gestational sac growth rate should be approximately?
1mm per day
what is Beta-hCG correlation?
- evidence of a developing intrauterine pregnancy should be seen transvaginally with serum beta-hCG greater that 1000-2000mIU/mL using the International Reference Preparation (IRP) standa
Alpha fetoprotein-AFP?
- produced by
- found in
- normal value
- produced by fetus
- found in amniotic fluid and maternal serum
- normal values vary with gestational age
causes of high AFP?
Underestimated gestational age Fetus older than expected Multiple gestations Open neural tube defect Abdominal wall defect Cystic hygroma Renal anomalies Fetal demise
causes of low AFP values?
Overestimated gestational age Fetus younger than expected Chromosomal abnormalities Trophoblastic disease Long-standing fetal demise Chronic maternal hypertension Diabetes
The sonographic presence of the yolk sac in an early gestational sac can be a predictor of?
a normally progressing pregnancy before visulization of the embryo
With TVS: Gestational sac measuring ____ mm should demonstrate a yolk sac?
<8mm
a <8mm yolk sac is consistent with what week gestation?
5- 5.5 week gestation
yolk sac on u/s?
- a round anechoic structure with an echogenic rim
what does a yolk sac supply?
- nutrition for developing embryo through the vitelline duct
what should the yolk sac and embryo be separated by?
- echogenic amnion but connected by the vitelline
size of yolk sac in 1st trimester?
2-6mm
an abnormally small or large measurement of a yolk sac may be indicative of?
- pending loss or fetal abnormality
how is the yolk sac diameter measured?
- with placement of capilers along the inner borders of the echogenic ring (AP)
the yolk sac is often used to assist in locating?
the developing embryo an dpossible cardiac activity
what characteristics of a yolk sac are associated with a poor prognosis? (3)
- anomalies of the size
- shape
- echogenicity
after the gestational sac has formed and the yolk sac has developed what is seen?
embryo
the embryonic period is considered to be week?
6-10 of the pregnancy
the embryo grows at a rate of?
1mm per day
initially, where is the embryo found and what does it appear as?
- found adjacent to the yolk sac
- appears as a flat, disc-like structure
Faint flickering of this structure, which represents early cardiac activity, may be seen on real-time sonography at?
- 5.5 weeks or when the CRL measures 5mm
With transabdominal technique, the embryo should be visualized in a gestational sac that measures?
25mm
The normal embryonic heart rate range is?
120-180 bpm
If the embryonic heart rate is 100 beats per minute or less what steps should be taken?
- it should be compared with the maternal heart rate to ensure that maternal uterine vessels are not being sampled and inaccurately represented as embryonic cardiac activity
what does an embryo begin a C-shaped appearance?
8 weeks GA
where can the cystic rhombencephalon be seen?
in the posterior embryonic head
at 8 weeks what might be seen?
- cystic rhombencephalon
- limb buds
If there is more than one first-trimester scan with a mean sac diameter or crown-rump length measurement, what should be used to determine the GA?
the earliest ultrasound with a crown rump length equivelent to at least 7 weeks (or 10mm)
the distinction between the head and torso of the fetus is more easily recognized at around what weeks?
11-12 weeks
An accurate CRL is obtained by placement of the calipers at?
the top of the fetal head (crown) to the bottom of the torso (rump)
care must be taken to not include what in a CRL measurement?
- yolk sac or fetal extremities
- avoid CRL measurement on an embryo or fetus that is flexed
By 11 weeks, it is easier to distinguish the fetal head and torso; however, obtaining a CRL at this stage can be challenging because of?
fetal flexion
what is nuchal translucency measurement performed?
- during a sono exam at the 1st trimester as an early screening tool for possible fetal aneuploidy
The nuchal translucency (NT) refers to?
the normal subcutaneous translucent space along the back of the fetal neck
A thickened NT is associated with? (4)
- fetal aneuploidy- trisomy 21
- genetic syndromes
- structural anomalies
- adverse outcome
Before the NT measurement is used what must be assessed?
- GA must be assessed with the CRL
The NT may be evaluated with a CRL of no less than?
45mm and no more than 84mm
45mm and 84mm corresponds to what GA?
- 11+0 and 13+6 weeks
The NT is considered to be thickened if it measures?
3.5mm or more during time frame
The risk for adverse outcome increases as what increases?
NT
what plane is used for a NT measurement?
sagittal
What is the cystic space visualized developing within the embryonic head at approximately 8 weeks’ gestational age?
Rhombencephalon
Evidence of a developing intrauterine pregnancy should be recognized endovaginally at which of the following serum beta-hCG levels?
1000- 2000 mIU/mL
The absence of the thick echogenic rim surrounding the early gestational sac within the endometrial cavity is suspicious for which of the following conditions?
Pseudogestational sac of ectopic pregnancy
In the development of a normal intrauterine pregnancy, the yolk sac should be demonstrated transvaginally in a gestational sac with what minimum measurement?
8mm
A secondary yolk sac measuring greater than what measurement is considered to be abnormal and suspicious for abnormal pregnancy development?
6mm
A primary role of sonography in evaluating pregnancy in the first trimester is confirmation of? (4)
- If the crown-rump length measures 5 mm and cardiac activity is not seen, the diagnosis of embryonic death can be made with confidence
- Failure to meet other first-trimester sonographic milestones should be noted
- A subchorionic hemorrhage may also lead to pregnancy loss
- Ultrasound may be used to follow bleeding with pregnancy to monitor viability, to confirm fetal death, and to determine when dilatation and curettage (D&C) is necessary
if CRL measures ____mm and cardiac activity is not seen, the diagnosis of embryonic death can be made with confidence?
5mm
what might lead to pregnancy loss in the 1st trimester?
subchorionic hemorrhage
what is a subchorionic hemorrhage?
- low-pressure hemorrhages that occur most commonly in the 1st trimester of pregnancy
what do subchorionic hemorrhages often result from?
- implantation of the fertilized ovum into the uterus
where are subchorionic hemorrhages commonly seen?
- between the uterine wall and the membranes
- are not associated with the placenta
s/s of subchorionic hemorrhage?
- spotting or bleeding with or without uterine contractions
outcome of a subchorionic hemorrhage?
- may spontaneously regress or may lead to spontaneous abortion (SAB)
A subchorionic hemorrhage prognosis is favorable when?
- fetal heartbeat is identified in the presence of a small hemorrhage
Hemorrhage in the lower uterine segment has a better prognosis than hemorrhage located at the uterine fundus T or F?
T
Subchorionic Hemorrhages in 13-week gestation is located?
adjacent to the GS and at the margin of the placenta
what can help differentiate hematoma from a neoplasm?
lack of vascularity identified with color doppler
what are the 3 classifications of a spontaneous abortion?
- threatened abortion
- missed abortion
- complete abortion
what is a threatened abortion?
- bleeding without cervical dialation
what is a missed abortion?
- embryonic death without expulsion of the products of conception
what is a complete abortion?
- when there is expulsion of the products of conception
what does risk of SAB decrease dramatically?
12 weeks
what can be used to confirm whether or not the sonographic milestones of a first-trimester pregnancy are met?
Correlation between the serum β human chorionic gonadotropin (β-hCG) and the findings in the uterus
en the gestational sac measures 25 mm (TAS) what should be identified?
embryo
Anembryonic pregnancy should be considered when?
an empty gestational sac is seen when the gestational sac measures 25mm (TAS)
when the embryo measures ____mm you should see cardiac motion
5mm
Embryonic bradycardia?
< 85 beats per minute in a gestation less than 7 weeks’ gestational age
<100 beats per minute from 7 weeks’ gestational age forward
TAS and TVS MSD should always see YS?
TAS: MSD 20 mm should always see YS
TVS: MSD 8mm should always see YS
TAS & TVS MSD you should see embryo?
TAS: MSD 25mm should see Embryo
TVS: MSD 16mm should see Embryo
what is a leading cause of maternal death in the 1st trimester?
ectopic pregnancy
risk factors of ectopic pregnancy?
- history of ectopic pregnancy
- PID
- tubal surgery
- maternal congenital anomalies
- later primiparity
- defective zygote
- fertility treatments
- intrauterine device (IUD) usage
Interstitial or cornual pregnancy occurs in what % of ectopic pregnancies?
2-5%
Ovarian pregnancies occur in what % of ectopic pregnancies?
- 2%
heterotopic pregnancy =
intrauterine pregnancy + ectopic pregnancy
S/S ectopic pregnancy (8)?
Intrauterine pseudosac or decidual reaction Positive pregnancy test Poor correlation with B-hCG Bleeding and severe pain Cul-de-sac fluid Adnexal ring sign Complex adnexal mass with or without live pregnancy Significant amount of hemoperitoneum
what is Gestational Trophoblastic Disease?
- spectrum of diseases of the trophoblast that can be benign, malignant, or malignant/metastatic
Gestational Trophoblastic Disease includes? (5)
- Complete hydatidiform mole
- hydatidiform mole with coexistent fetus
- partial mole
- invasive mole
- choriocarcinoma
risk factors of gestational trophoblastic disease? (2)
- maternal age
- previous history of a molar pregnancy
what is a sign of gestational trophoblastic disease?
hyperemesis
s/s of molar pregnancy?
- vaginal bleeding
- hyperemesis
- preeclampsia
- thyrotoxicosis
- respiratory distress
B-hCG in molar pregancy?
- elevated- >100 000 IU/mL
in what molar pregnancy are maternal serum AFP levels low?
complete hydatidiform mole
s/s molar pregnancy?
- uterus greater in size than expected GA
- bilateral ovarian enlargement
- theca-lutein cysts
what is a Complete hydatidiform mole?
Paternal origin and devoid of maternal chromosomes which results in a 46,XX karyotype without fetal development
what are partial moles?
- Triploidy with a 69,XXX or 69,XXY karyotype, of which 23 chromosomes are of the maternal contribution and 46 chromosomes are of the paternal contribution
- May be accompanied by a fetus or fetal tissue
rarely what kind of mole may also coexist with a normal fetus as the result of a twin gestation?
complete hydatidiform
Invasive Hydatidiform Mole?
when the hydropic villi of a partial or complete mole invade the uterine myometrium and sometimes uterine wall
Invasive Hydatidiform Mole may occur during?
during the development of a complete or partial mole (although rare with partial mole) or may develop after the evacuation of a mole
clinical symptoms of Invasive Hydatidiform Mole?
typically become apparent after the evacuation of a molar pregnancy, when the patient presents with heavy bleeding
what is Choriocarcinoma?
- A malignant tumor that arises from the trophoblastic epithelium
- Considered a malignant metastatic form of gestational trophoblastic disease
- May metastasize to the lung, skin, intestines, liver, spleen, heart, and brain
- Treatment is chemotherapy
Choriocarcinoma s/s?
Vaginal bleeding + enlarged uterus and ovaries + elevated β-hCG levels
Choriocarcinoma may develop when?
- after a molar pregnancy
- can also occur after a normal pregnancy, SAB, or ectopic
