exam 1 - pregnancy dx Flashcards
A 16 yo girl, LMP 10 weeks ago, presents for a pregnancy test. The pregnancy test is positive. She requests a blood test because she has heard “those pee tests aren’t reliable”.
WRONG: urine pregnancy tests =:
-extremely accurate and reliable (>99% accurate)
-often positive days after conception
-should be positive by 1st missed period
-a positive result corresponds to a serum quantitative bHCG of at least 20mlU/ml
quickening definition and use
-never use this to dx pregnancy
-The first fetal movements perceived by the patient
-Primigravidas: 20 weeks GA
-Multigravidas: 16-20 weeks GA
-Considered by Aristotle and by the Abrahamic religions to be the time of “ensoulment” of the fetus
-Not used to make diagnosis of pregnancy
PE findings that were previously used to dx pregnancy
Chadwick’s sign (pic)
-Cyanosis of cervix and vagina at 6-8 weeks
-blood is going to the pelvis
-so much blood it looks purple
-normal but looks hypoxic
Hegar’s sign
-Softening of uterine corpus at 6-8 weeks
Both of these entities are commonly included on the PANCE and PANRE!
methods of absolutely dx pregnancy without urine or blood
1) auscultation or measurements of fetal heart rate while measuring maternal heart rate:
- 2 different heart rates indicate pregnancy
-the corollary is also important
-in cases of maternal tachycardia, be certain to document 2 separate and distinct heart rates
2) clinician palpates fetal movements
3) radiologic evidence of fetus:
-U/S
-flat plate of abdomen or CT scan (often obtained in trauma)
urine pregnancy tests
-extremely accurate and reliable (>99% accurate)
-often positive days after conception
-should be positive by 1st missed period
-a positive result corresponds to a serum quantitative bHCG of at least 20mlU/ml
false positive pregnancy tests causes
-Recent pregnancy (usually within one month of conclusion of pregnancy)
-Mixed samples
-Exogenous bHCG administered as part of infertility treatment
-Choriocarcinoma (malignancy arising from the placenta) -> May represent initial presentation, or recurrence of disease
false negative pregnancy tests causes
-very early pregnancy
-mixed samples (someone switched the samples)
reasons to obtain a serum bHCG
-almost never necessary to obtain serum to dx pregnancy
MC reason to order quantitative serum bHCG is to RULE OUT ECTOPIC PREGNANCY:
-normally bHCG doubles every 48 hrs in 1st trimester (ectopic normally wont do that)
-a normal intrauterine pregnancy will demonstrate this pattern
If serum bHCG levels plateau or fall, consider these dx:
-ectopic or impending abortion
-intrauterine pregnancy can be seen (yolk sac, fetal pole) via transvaginal US with bHCG > 1500 or via transabdominal US with bHCG >6000 -> this is known as the DISCRIMINATORY ZONE
-by 2000 you should see on US
ectopic pregnancies are generally located in the fallopian tube
-but can be elsewhere
-in the cervix
-in an old c section scare (very rare)
-in the ovary
-abdominal
lithopedion
-stone + child
-fetus dies in the abdomen and is found on accident
in which of the following circumstances should an intrauterine gestational sac be visible on transvaginal US
-HCG of 260
-HCG of 730
-HCG of 1150
-HCG of 2120**
