Antenatal Investigations

Last updated 26.09.12

   

Definition

-  Investigations performed prior to, at confirmation of & throughout pregnancy to screen for & monitor complications &/or diseases which may impact on mother &/or fetus

 

Features

-  Serology tests best performed prior to pregnancy

-  CMV serology is useful prior to pregnancy

-  First tests usually performed between 4-12/40 at first antenatal visit

 

Routine Antenatal Ix

-  At first visit or as part of preconception counselling

-  Antenatal bloods are kept for 12 months in all Australian laboratories therefore can do add ons as needed

-  Blood

-  +/- Beta HCG

-  Positive 10-14/7 post conception, 4 weeks+ from LMP

-  To confirm pregnancy

-  FBE

-  Hb/RBC

-   Baseline

-   Anaemia: thalassaemia, IDA

-  Physiological anaemia: total blood volume increases 40-45%, RBCs 33% increase 

-  +/- further Ix as indicated

-  Platelets: thrombocytopaenia

-   <150 Pre-eclampsia, gestational thrombocytopaenia

-   <100 ?HELLP

-  Blood Group & Rhesus

-  Cross matching only if required

-  Rhesus antibodies: Rhesus Isoimmunisation

-  Repeat at 28/40 if Rhesus negative

-  Infectious Serology

-  Rubella

-  Aim to prevent congenital rubella

-  May require pre-pregnancy immunisation or post partum

-  Syphilus (TPHA)

-  +/- repeat at 28/40 & at delivery if high risk population

-  Aim to prevent congential syphilis by screening & treatment

-  HIV (with informed consent)

-  +/- repeat at 28/40 if prev negative & high risk behaviour

-  Aim to prevent vertical transmission

-  Document consent of woman & pre-test counselling

-  Early detection & Mx decreases rates of vertical transmission

-   Zidovudine, Nevirapine, elective LUSCS, avoiding breast feeding

-  Hepatitis Serology

-  HBV by HBs Ag: HBV in pregnancy

-  HCV by Anti-HCV Ab: HCV in pregnancy

-  +/- VZV by IgG: VZV in pregnancy

-  Aim to prevent fetal varicella syndrome

-  If no Hx of infection (Chicken Pox or Shingles) or unsure

-  May require pre-pregnancy immunisation

-  Urine Dipstick + MSU for MCS

-  Protein >1+: Pre-eclampsia

-  Nitrites, Leukocytes: UTI/Asymptomatic bacteruria

-  Glucose >1+: perform OGTT for DM in pregnancy

-  Ketones: Hyperemesis gravidarum

-  At risk populations

-  +/- Iron studies: IDA

-  +/- Haemoglobin electrophoresis: haemoglobinopathy

-  +/- Vitamin D levels: Vitamin D Deficiency

-  +/- B12: deficiency: vegans, Pernicious anaemia, bowel resection

-  +/- TSH (Thyroid disease in pregnancy) if

-  Known thyroid disease

-  Family Hx of thyroid disease

-  Suspected iodine deficiency

-  S/S of hypothyroidism or hyperthyroidism

-  DM type 1

-  +/- Chlamydia urinary PCR: teenage pregnancies (or <25yrs) or multiple partners

-  +/- Ultrasound: Dating Scan if needed

 

Follow Up Ix

-  11-14/40

-  Combined First Trimester Serum Screening

-  9-14/40 Nuchal Translucency (Down Syndrome)

-  11-14/40 Beta HCG + PAPP-A

-  +/- Nasal bones

-  +/- OGTT if risk factors for GDM

-  12-16/40

-  Urine MSU for MCS: UTI, asymptomatic bacteruria

-  18-20/40

-  Morphology Scan & placental position

-  26-28/40

-  OGTT if no risk factors or Normal in first trimester: GDM

-  28-30/40

-  If Rh –ve: Rhesus antibodies + Anti-D administration

-  33-36/40

-  FBE: Anaemia

-  +/- If Rh –ve: Rhesus antibodies + Anti-D administration

-  35-37/40

-  +/- LVS: Group B Strep (if done at institution)

 

Ultrasound

-  1st Trimester

-  Consider Dating Scan once known pregnant at 9/40+/-

-  Viability & location of pregnancy: miscarriage, ectopic, PUL, PUV

-  Accurate dating for timing of screening (NT) & IOL

-  Hyperemesis: multiple gestations (twins..), gestational tropholbastic disease

-  PV Bleeding: Miscarriage, APH

-  11.5–14 weeks: Nuchal Translucency (Down Syndrome)

-  2nd Trimester

-  18–20 weeks: Morphology Scan & placental position (vasa praevia, placenta praevia)

-  3rd Trimester

-  SGA or LGA

-  Previous IUGR

-  Multiple pregnancies: twin..

-  Complications of pregnancy

-  Antepartum Haemorrhage (APH)

-  TPL/PROM

-  Maternal disease: DM, CRF..

-  +/- Biophysical profile: high risk women

 

Antenatal Dx

-  Nuchal Translucency & Triple Test

-  Amniocentesis

-  CVS

 

 

 

References

 

Western Diagnostic Pathology: Pregnancy Timeline of Lab Tests

Routine Antenatal Screening, A. Mellor, O&G Magazine, Vol 11-2, 2009

3Centres: Number & Timing of Routine Antenatal Visits, 09/08/2010

3Centres: Antenatal Screening for HBV, 06/08/2010

3Centres: Antenatal Screening for HCV, 06/08/2010

3Centres: Antenatal Screening for HIV, 06/08/2010

3Centres: Antenatal Screening for Syphilis, 06/08/2010