Pregnancy Testing

Your pregnancy and fertility guide to everything from routine blood work to genetic screening at the doctor's office.

Pregnancy Testing

Illustration by Anke Weckmann

As her pregnancy progressed, Anne Smith,* 40, eventually got used to being poked, prodded and pricked with needles every time she visited her obstetrician, but she didn’t always know what the tests were for. “I basically just did whatever I was told,” says the Toronto mom. “But I was clueless. I didn’t know why they were doing all the tests and no one at the office ever really had the time to explain them to me.”

Ideally, your first appointment will occur in the first 12 weeks of pregnancy. This visit may include a pregnancy test to confirm your mom-to-be status, a thorough head-to-toe checkup and an examination of your family’s medical history. Here are some other routine prenatal tests to expect over the course of your pregnancy.

Blood Work

Prenatal blood tests identify your blood group, hemoglobin level, iron, blood sugar levels, immunity to infectious diseases like rubella (German measles) and whether you are Rhesus (Rh) positive or negative. If your blood group is Rh-negative (85 percent of people are Rh-positive), your blood may be incompatible with your baby’s. Women found to be Rh-negative are given an injection of Rh immunoglobulin, also called Rhogam, at 28 weeks and 72 hours after birth if the baby is Rh-positive. When: First medical appointment.

Urine Test

The urine test measures levels of sugar, protein, white blood cells or bacteria to determine if you might have diabetes, high blood pressure, kidney disease or a urinary tract infection. When: Every medical appointment.


This is your first chance to see your unborn baby and maybe even find out the sex. The test assesses the size and growth of your baby, the placement of your placenta and checks the fetus for abnormalities of the head and spine. When: Between 16 and 20 weeks. If there are concerns about the pregnancy (bleeding, history of miscarriage or ectopic pregnancy) your healthcare provider may recommend one be done between six and 10 weeks.

Glucose Screening

While most pregnant women are tested for gestational diabetes, those considered high-risk may be tested as early as 13 weeks. You’ll be given a high-sugar drink and, an hour later, your blood is drawn and tested for elevated glucose levels. If you test positive you will be referred to a specialist to help you manage your disease during the pregnancy. After delivery, glucose levels usually return to normal but you are at risk for developing type 2 diabetes later in life. When: Between 24 and 28 weeks.

Group B Streptococcus Test

This painless test determines whether you have Group B streptococcus present in the vagina which can cause life-threatening infections in newborns during a vaginal birth. The test involves swabbing the inside of the vagina and rectum. If the bacterium is detected, you will receive antibiotics during labour. When: Between 35 and 37 weeks.

Genetic Screening and Diagnostic Tests

Two to three percent of babies are born with major birth defects including certain chromosomal abnormalities (such as Down Syndrome), and the risks increase with the mother’s age, says the Society of Obstetricians and Gynaecologists of Canada (SOGC). At age 35, the risk is about 1:200. At age 40 it is about 1:70. Last year, the SOGC recommended that non-invasive genetic screening tests be made available to all women, regardless of age. However, many women still don’t know that screening exists, or are confused by the difference between screening and diagnostic testing, says Dr. Alain Gagnon, a perinatologist at B.C. Women’s Hospital and Health Centre in Vancouver. “The biggest misconception is that having a screening or diagnostic test means you want to have a termination,” he says. “For many women, it’s about preparation and optimizing care at time of delivery.” Genetic screening tests (such as a blood test-based maternal serum screen and early ultrasound) estimate your risks of having a child with chromosomal abnormalities and are designed to help you decide whether to have a more invasive, and therefore riskier, diagnostic test. These include Chorionic villus sampling (CVS), the removal of a small piece of tissue from the placenta, which can be done at 10 to 12 weeks gestation (it carries a higher risk of miscarriage), and amniocentesis, during which a sample of the amniotic fluid surrounding the baby is withdrawn. This test can only be performed after week 15.

Freelance writer Sydney Loney finally understands what all those prenatal tests were for — 19 months after the birth of her son.

* name has been changed

One response to “Pregnancy Testing”

  1. Kristie says:

    I am 37 in December. I have a son who is 2.5years old and just had a baby. She is 3.5months old. I am breast feeding. I had intercourse with my partner June 29,2012 and am now experiencing pregnancy symptoms. Is that possible? I welcome another child I just didn’t think it would be so soon. My partner and our families and friends have strong opinions about this. Aside from going to the doctor what signs are sure signs I’m pregnant?