Common tests during pregnancy

Ultrasound pregnancy examination of young woman in a Medical Clinic during Covid 19 outbreak.

Information provided by Dr. Howard Deosaran, obstetrician and gynaecologist, Centre for Women, Family and Child Health.

Dr. Howard Deosaran

Antenatal urine tests

Urine tests at each prenatal visit to detect blood, ketone, protein, bacteria and glucose.

Blood glucose tolerance test

A blood test at 24 to 28 weeks measures the level of sugar in patient’s blood. Abnormal levels may indicate gestational diabetes. Initial test is a glucose challenge test, with sugar levels tested one hour after drinking a glucose solution. In the case of abnormal results, a follow up glucose tolerance test is required, which involves blood being drawn at various times over the course of several hours after drinking a glucose solution.

Genetic screening

Optional or may be recommended if family history of genetic disorders. Can be done by multiple marker test, amniocentesis, chorionic villus sampling, cell-free DNA testing, percutaneous umbilical blood sampling, or ultrasound scan.

Iron deficiency anaemia testing

Blood test at first prenatal visit, and around 28 weeks. Anaemia during pregnancy can cause problems for both mother and baby.

Pap smear

Usually done at first prenatal visit for cervical dysplasia. An HPV ((human papillomavirus) test can also be done.

Pertussis/Tdap (whooping cough) vaccination

Given at 28 weeks and 34 to 36 weeks. Protects mother and baby against whooping cough.

Rh factor testing

If you don’t know your blood type you may be tested to see if your blood type is Rhesus negative or positive. If negative, and the baby’s father is positive, or does not know his blood type, you will be given a Rho(D) immune globulin (RhoGAM) injection at 28 weeks, and again within 72 hours of delivery if your baby is Rh positive. RhoGAM would also be given after any other event that could result in mixing of maternal and foetal blood, for example chorionic villus sampling, amniocentesis, vaginal bleeding or trauma during pregnancy, miscarriage, ectopic pregnancy or abortion.

Ultrasound

Abdominal or transvaginal 2-D ultrasounds are available, as well as 3-D or 4-D scans although these are not routine. Used to establish due date, diagnose ectopic pregnancy or miscarriage, examine uterus, detect some foetal abnormalities, check amniotic fluid, observe foetal behaviour, examine blood-flow patterns, monitor foetal growth, assess placenta, and measure length of cervix. The number of ultrasounds offered will vary by practitioner, but commonly include a first trimester sonogram and a 20-week anatomy scan.

Vaginal swab for Group B strep (GBS)

Taken between 34 and 37 weeks. Tests for GBS, a type of bacteria which can cause illness during pregnancy. GBS may cause chorioamnionitis, postpartum infection and urinary tract infections. Newborns can contract infection during pregnancy or labour and delivery.

Weight and height checks

These will be checked at first prenatal check, and your weight may be checked again throughout your pregnancy, with frequency dependent on practitioner.

Weight measurement

The amount of weight you gain during pregnancy is important for the health of the pregnancy and for the long-term health of you and your baby. How much weight you gain during pregnancy is based on your body mass index (BMI). Pregnant with one baby: normal weight BMI of 25-29.9; you should gain 25 to 35 lbs. Pregnant with twins: normal weight BMI of 18.5-24.9; you should gain 37 to 54 lbs.

Urinalysis

Involves checking the appearance, concentration and content of urine. It screens for a variety of disorders such as diabetes, kidney disease and liver disease.

Blood pressure measurement

A normal blood pressure is 120/80. Blood pressure (BP) is measured in units of millimetres of mercury (mmHg). BP below 90/60 mmHg indicates hypotension. BP above 140/90 mmHg in pregnancy indicates hypertension. An abnormal BP during pregnancy is cause for concern. Both mother and baby may be at an increased risk of health complications.

Foetal monitoring

Done throughout the pregnancy.

1. Transvaginal scan to 12 weeks gestation.
2. Transabdominal scan from 12 weeks.
3. Nonstress test done in the office.
4. Daily foetal kick chart done by the patient, usually at 34 weeks.
5. Cardiotocography at labour and delivery monitors foetal heart rate and contractions of the uterus.

Genetic screening

1. Cell-free DNA – blood test from nine weeks gestation.
2. Alpha feto-protein test.
3. Amniocentesis.
4. Chorionic villus sampling.
5. Percutaneous umbilical blood cord sampling.

Blood studies

1. At 12 weeks, gestion include: HIV, Hep B, C, blood group and Rh, HB electrophoresis, Rubella, COVID-19 Ig G antibody, cytomegalovirus Ig G and Ig M, toxoplasmosis Ig G, Ig M.
2. At 26-28 weeks gestation: O’Sullivan’s screen for gestation diabetes. If the value is greater than 135, then the patient will have an oral glucose tolerance test which includes: fasting glucose and 1-hour, 2-hour and 3-hour glucose testing.
3. Complete blood count at 36 weeks to ensure no anaemia prior to delivery.

Swabs Ÿ

  • HVS (high vaginal swab) at booking to rule out Group B Streptococcus (GBS) Ÿ
  • ECS (endocervical swab) at booking to rule out chlamydia. Ÿ
  • HVS at 34 to 37 weeks for GBS.