Maximal absorbance of bilirubin

Specimen requirements?

450nm

minimal blood contamination, protect from light

Degree of fetal hemolysis

whict test?

Amniotic fluid bilirubin

--> serial measurements ~ estimated GA

= Glycoprotein --> a-subunit --> TSH,FSH.LH

--> beta-subunit--> immunoassay

false - hCG_urine

Causes?

Dilute urine

Hook effect

--> confirm with hCG_serum

false + hCG_serum

Cause?

heterophile Ab interference

-->repeat on different analyzer/pretreat w heterophile binding reagent/run serial dilutions

low level "phantom" hCG

No a/w pregnancy or overt gestational trophoplastic disease - Causes & Rx

1. Pt w appropriately treated GTD

2. ~incidental, rare--> pituitary tm

Rx: none if no anatomic lesion is identified

hCG in normal pregnancy

Detectable - when?

Plateaus- when?

6-8 wks post conception ~ implantation

early 2nd trimester - plateaus @ 10,000 ( 800ng/ml)

*end of 1st trimester = 100,000 

hCG remains detectable for how long after?

1.delivery

2. spontaneous abortion

3.evacuation of uncomplicated molar pregnancy

1. 2wks --> triphasic

2. 4-6 wks

3. 10 wks

Female with abdominal pain / mild vaginal bleeding

hCG_serum <66% in 48hrs

DDx

Ectopic¹ / spontaneous abortion

¹15% --Normal rate of rise

15% of normal IUP--> abnormal rate of rise

Clinical: Uterine enlargement out of proportion for GA

vaginal bleeding, HTN, absence of fetal heart tones

hCG >> normal -Dx?

Complete mole-->risk of malignancy 20%(Partial-->5%)

hCG_complete> hCG_partial

"Clinical --> Complete"

50% --> post normal term pregnancy

25% -->post histologically normal spontaneous abortion

25% --> molar pregnancy

1.[hCG,AFP & unconj Estriol]¹_{maternal serum}~ 18wks (Sens=70%)

2."Quad test" =¹ + dimeric inhibin A -->stable in 2nd Trim (Sens=80%)

¹affected by inaccurate GA estimation

3. "Integrated screen" PAPP-A&hCG 1st trim,AFP, uE & DAI 2nd trim

- decrease in uE & hCG

- increase in AFP_maternal

decrease AFP, hCG,uE

dx?

Trisomy 18 (Edward syndrome)

"Edward = 18 --> vampire"

increased AFP, MSAFP¹

nml hCG

decreased uE - Dx?

Neural tube defect

¹twin gestation

increased hCG

decreased AFP & uE

Dx?

Trisomy 21

Also--> elevated dimeric inhibin A

AFP

MSAFP--> ~ maternal weight, race, # of fetuses, maternal diabetes

Estriol_{serum/salivary} --> increse prior to the onset of preterm labor

bacterial vaginosis

Fetal fibronectin, transvaginal cervical U/S

Fetal fibronectin

Positive and negative predictive value

Causes of false elevation

PPV = low , NPV = high

specimen collection<24hrs s/p cervical exam/intercourse

Uncontaminated amniotic fluid

--> GA 34-37 wks

Lecithin/sphingomyelin ratio (normal 2:1@35 wks)

problems in interpretation

DM --> phosphatidylglycerol --> more reliable

Meconium --> decreases L:S ratio

Blood --> normalizes L:S to 1.5

CV of L:S --> high

Fluorescence polarization assay--> rapid test w lower CV

Contaminated amniotic fluid

Tests of choice for determination of lung maturity

[Phosphatidylglycerol]--> first detected @ 36 wks

[disaturated phosphatidylcholine]=lecithin major component 

Lamellar body number density

Method of measurement

Surfactant lamellar bodies ~> size of platelets

=> cell counter platelet channel

>50,000/mL => lung maturity

Physiologic changes in pregnancy

- Triglycerides

-Albumin & total protein

-GFR

~40% increase

decreased<-- hemodilution

increased<-- increased BV

after mid-2nd trimester --> increased insulin resistance

<-- hPL --> anti-insulin effects~GH

Na⁺ & K⁺ ~ constant

Ca²⁺ --> falls slightly

 SLE flare¹ vs. pregnancy induced hypertension²

Test for Dx?

Complement levels

¹low , ²normal

Clean catch voided urine specimen

>100,000 col/mL

Pt: asymptomatic female - Dx & Rx & cause

Sheehan syndrome = postpartum pituitary apoplexy

<-- severe blood loss @ delivery & pituitary enlargement a/w pregnancy

Most common thyroid disorder in pregnancy

Best test -->thyroid status?

Hypothyroidismin Pt w borderline thyroid function/available iodine Estrogen--> incr.TBG, hCG-->TSH-like stimulatory effect

=>increased demand

Most common cause of hyperthyroidism in pregnancy

DDX?

Syndrome of transient hyperthyroidism of hyperemesis gravidarum <-- high levels of hCG ~ TSH-like effect

DDx: true hyperthyroidism

Recurrent Pregnancy loss

Endometrial biopsy: >2d discrepant with dates

Dx?

Recurrent Pregnancy loss

when and what tests?

≥ 2 spontaneous abortions

parental karyoting (+abortus), endometrial bx / cultures (subclinical Ureaplasma/Chlamydia infection)

Thyroid function tests, lupus anticoagulants

Liver bx in pregnant woman: Widespread microvesicular steatosis, accentuated paracentrally (zone 3)

Paucity of inflammatory activity/ hepatocellular necrosis

Dx?

Acute fatty liver of pregnancy (rare), usually 3rd trim.

complicated by DIC, 30% fatality rate

Liver bx in pregnancy:

Pericentral (zone 3) region: dilated canaliculi containing bile plugs - Dx

Most characteristic lab finding?

Intrahepatic cholestasis

increased [Bile acids]_serum

HbA1c in pregnancy

Alternative test?

hormonal changes cause greater short-term fluctuation in [glucose]

fructosamine : 2-3wks