diagnosis of pregnancy

- Dr. Neelesh Bhandari M.B.B.S (AFMC), M.D. (Path) P.G.P in Human Rights.

Early pregnancy detection allows

• the commencement of prenatal care, • potential medication changes,

• lifestyle changes to promote a healthy pregnancy (appropriate diet; avoidance of alcohol, tobacco, and certain medications),

• early pregnancy termination if so desired.

Pregnancy can be diagnosed by 3 approaches.

1. Physical examination

2. Laboratory evaluation

3. Ultrasonography

Early Physical signs of pregnancy • Blue discoloration of the cervix and vagina (

Chadwick's sign) • Softening of cervix (Goodell's sign) • Softening of uterus (Ladin's sign and Hegar's sign) • Darkening of the nipples

• Unexplained pelvic or abdominal mass

• Breast and nipple tenderness

• Nausea

• Urinary frequency

Physical signs of pregnancy…

• The most commonly used assays are for the beta subunit of hCG

Other hormones that have been used for diagnosis-• progesterone

• early pregnancy factor (EPF).

Laboratory Investigations

• This hormone is only released by trophoblastic tissue produced by a growing fetus and its associated placenta. • hCG is present in the maternal circulation as either an intact dimer, alpha or beta subunit, and degraded form, or beta core fragment

• Detection of HCG in maternal serum and urine is evident only 8-10 days after conception

• hCG is detectable in the serum of approximately 5% of patients 8 days after conception and in more than 98% of patients by day 11

• Diagnostic levels in Urine seen only about 23-24 days after conception.

• Levels peak at 10-12 weeks' gestation and then plateau before falling

In general, the HCG level will double every two to three days in early pregnancy

Detects presence of HCG in Urine sample.• Easy to perform.• Inexpensive compared to Blood tests

Most current pregnancy tests have sensitivity to approximately 25 to 35 mIU/mL (ranges from 25 to 100mIU/mL).

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After 3 drops of urine are placed in the "S" basin, a sold line appears at the "C" area. After a minute, another line appears at the "T" area, indicating that this patient is pregnant.

Home Pregnancy Tests

kits available for hCG detection in urine via - Direct Latex agglutination and/or- Indirect Agglutination inhibition tests.

• HPTs are most commonly used in the week after the missed menstrual period (fourth completed gestational week).

• Urine hCG values are extremely variable at this time and can range from 12 to 2500 mIU/mL.

Currently, 4 main hCG assays are used,

(1) radioimmunoassay,

(2) immunoradiometric assay,

(3) enzyme-linked immunosorbent assay (ELISA),

(4) fluoroimmunoassay.

- Used only in special cases ( bad obstetric history, suspicion of ectopic,etc.)- Require special labs and expertise.

Radioimmunoassay Sensitivity - 5 mIU/mL Time to complete - 4 hours Postconception age when first positive - 10-18 days Gestational age when first positive - 3-4 weeks

Immunoradiometric assay (more sensitive) Sensitivity - 150 mIU/mL Time to complete - 30 minutes Postconception age when first positive - 18-22 days Gestational age when first positive - 4 weeks

Immunoradiometric assay (less sensitive) Sensitivity - 1500 mIU/mL Time to complete - 2 minutes Postconception age when first positive - 25-28 days Gestational age when first positive - 5 weeks

Enzyme-linked immunosorbent assay (more sensitive) Sensitivity - 25 mIU/mL Time to complete - 80 minutes Postconception age when first positive - 14-17 days Gestational age when first positive - 3.5 weeks

Enzyme-linked immunosorbent assay (less sensitive) Sensitivity - Less than 50 mIU/mL Time to complete - 5-15 minutes Postconception age when first positive - 18-22 days Gestational age when first positive - 4 weeks

Fluoroimmunoassay Sensitivity - 1 mIU/mL Time to complete - 2-3 hours Postconception age when first positive - 14-17 days Gestational age when first positive - 3.5 weeks

Failure to achieve the projected rate of rise (slow rise) may suggest an ectopic pregnancy or spontaneous abortion.

On the other hand, an abnormally high level or accelerated rise can prompt investigation into the possibility of • molar pregnancy, • multiple gestations, • chromosomal abnormalities.

False-positive hCG• Phantom hCG - Rule out with sensitive urine assay, as these

antibodies do not cross into urine

• Pituitary hCG - Diagnosed by administering oral contraceptive pills, which should suppress hCG levels

• Exogenous administration of hCG

• Trophoblastic neoplasm – e.g. Choriocarcinoma • Nontrophoblastic neoplasm - Can be secreted by different

cancers, (e.g., testicular, bladder, uterine, lung, liver, stomach)

Most false-positive results are characterized by serum levels that are generally less than 1000 mIU/mL and usually less than 150 mIU/mL

usually involve urine and are due to the qualitative nature of the test. Reasons include –

• an hCG concentration below the sensitivity threshold of the specific test being used.

• a miscalculation in the onset of the missed menses,

• delayed menses from early pregnancy loss.

• Delayed ovulation or delayed implantation.

False-negative hCG

• Measurement of serum progesterone is inexpensive

• Done by Radioimmunoassay and Fluoroimmunoassay

• Can reliably predict pregnancy prognosis.

A dipstick ELISA that can determine a S.Progesterone level of less than 15 ng/mL is also on the market.

ELISA is helpful as a screening tool for at risk populations because progesterone levels of greater than 15 ng/mL make ectopic pregnancy unlikely.

• Serum progesterone levels greater than

25 ng/mL Viable Intrauterine Pregnancy

• Serum progesterone levels of less than 5 ng/mL Nonviable pregnancy.

Early pregnancy factor

• Earliest available marker to indicate fertilization (detectable 36-48 hours after fertilization). • Peaks early in first trimester, almost undetectable at term.

• Appears within 48 hours of successful IVF embryo transfers.

• Vanishes 24 hours after delivery (or at the termination of pregnancy) • Detected by rosette inhibition test.

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Ultrasound

The identification of gestational structures by US correlates with specific levels of hCG, termed discriminatory levels. • A discriminatory level is the level of hCG at which the structure in question should always be identified.

• Most experienced TVUS operators should visualize the GS when levels are approximately 1000 mIU/mL.

• The discriminatory level for the GS is approximately 3600 mIU/mL, and if it is not seen at this point, other pathology must be excluded.

GS – Gestational Sac

• The yolk sac is commonly observed with an hCG level of approximately 2500 mIU/mL,

• The embryonic pole usually becomes evident at a level of approximately 5000 mIU/mL,

• Fetal heartbeat can be seen in the vast majority of normal gestations when the hCG level reaches 10,000 mIU/mL.