First Trimester Blood and Urine Tetss
When you go to the lab to confirm a pregnancy, you may be surprised at the number of vials of blood taken - I sure was! Besides beta-hCG, many more things are tested. Some of these are routine tests that should be done in the first trimester to establish things like deficiencies or antibodies. And some, are variable - they can be dependent on your age, health history, even your diet.
First trimester blood work is important because it gives health care providers an opportunity to identify and address potential issues early in pregnancy, in the hopes that it will lead to better outcomes for both mom and baby.
First Trimester Blood Tests
beta-hCG
This is commonly known as the pregnancy hormone, as it quickly increases during pregnancy. Beta-hCG can be detected via blood test 11 days after conception, while it can be detected via urine 12-14 after conception.
One single beta-hCG test cannot diagnose the viability of a pregnancy or where the pregnancy is. Multiple tests, as well as an ultrasound are needed.
Typically people who are being seen by a fertility clinic may have their b-hCG tested often to ensure that the number is steadily doubling.
Blood Type and Rh Factor
Blood group typing and antibody screening is done in the first trimester to establish the mom’s blood type, as well as their Rh factor. The Rh factor is a protein on red blood cells that’s either positive (the protein is there) or negative (the protein is not there). You know it as the O+ or A-.
Problems may arise during pregnancy with differences in the Rh factor between mom and baby. If a Rh-negative woman is pregnant with an Rh-positive fetus, her body may develop antibodies against the fetus' blood, leading to fetal anemia or jaundice.
When the blood of an Rh-positive fetus gets into the bloodstream of an Rh-negative woman, the mom’s body will recognize that the Rh-positive blood is not hers and her body will make anti-Rh antibodies to cross the placenta and attack the blood cells of the fetus. This may can lead to detrimental health outcomes - the most significant being death.
To prevent Rh incompatibility issues, Rh-negative women can receive Rh immunoglobulin (RhIg), a medication that prevents antibody formation, after situations like miscarriage or invasive procedures. Regular antibody screenings can determine if a woman has developed Rh antibodies, especially if there is a chance of carrying an Rh-positive fetus.
Complete Blood Count & Ferritin
Iron is the most common nutritional deficiency in women, with a high percentage having iron deficiency. During pregnancy, iron deficiency is associated with increased maternal illness, antenatal and postnatal depression, and a higher risk of cesarean delivery. In the developing baby, low iron levels are associated with low birth weight, prematurity, and intrauterine growth restriction.
One caveat is that during the first few weeks of pregnancy, ferritin may be artificially elevated. This is because ferritin is an acute phase reactant, meaning its levels can rise in response to systemic inflammation. Pregnancy itself can cause some degree of inflammation in the body.
This is why a complete blood count (CBC) is routinely run, to give an idea of hemoglobin levels and if a true iron deficiency exists.
Ferritin and hemoglobin are typically tested again, alongside the gestational diabetes test.
Hepatitis B
All pregnant people should be tested for hepatitis B surface antigen (HBsAg) during the initial prenatal visit, regardless of prior vaccinations or tests. Those people who are already diagnosed with chronic hepatitis B virus (HBV), this test confirms their HBsAg status and ensures that appropriate preventive measures are taken for their infants.
Pregnant people with HBV infections pose significant risks to their newborns, there’s a 90% chance of them developing chronic HBV. Undoubtedly, screening helps to reduce this risk through early testing, and ensuring timely treatment and vaccinations if necessary in the hopes of preventing mother-to-child transmission of the virus.
If the HBsAg test is negative but there are ongoing risk factors for HBV infections testing will likely be repeated later in pregnancy. These factors include:
Being born in an endemic country
Illicit drug use
Multiple sexual partners
Multiple transfusions
Immunosuppression
Having an HBV-positive partner
Being a healthcare worker
Rubella
If a pregnant person contracts rubella, it can lead to significant risks to their baby's health - especially if the infection happens in the first 12 weeks of pregnancy.
Rubella is generally considered a mild illness, typically presenting with flu-like symptoms followed by a pink or light red rash. This rash usually begins on the face and spreads across the body, lasting around three days.
Risks for the fetus include congenital rubella syndrome (CRS) which may lead to a number of of serious birth defects, such as heart problems, vision impairments, hearing loss, intellectual disabilities, low birth weight, and damage to the liver and spleen. Furthermore, miscarriage, stillbirth and preterm birth are also notable risks.
HIV
HIV is screened for as early as possible in the first trimester, and again in the third trimester. The reason is to ensure a timely diagnosis of HIV and quick therapy initiation, which may prevent transmission to the baby.
STIs
Gonorrhoea and chlamydia are common sexually transmitted infections screened for in pregnancy as they can lead to serious complications including preterm birth and low birth weight infants.
Furthermore, some STIs can also be passed from mother to child during pregnancy or childbirth, leading to severe health issues.
Urine Culture
This screens for and detects asymptomatic bacteriuria (ASB) and urinary tract infections (UTIs). ASB happens in 2 to 15% of pregnant women, and if left untreated, can lead to symptomatic UTIs in 20-35% of the time and a kidney infection up to 30% of the time.
Additional Testing
TSH
All pregnant people should be verbally screened at their initial prenatal visit for a history of thyroid dysfunction, as well as current/past use of thyroid medications.
TSH should be tested to prevent complications because untreated thyroid disorders during pregnancy can lead to various complications, including early pregnancy loss, preterm birth, preeclampsia, placental abruption, anemia, postpartum hemorrhage, and congestive heart failure. Moreover, proper thyroid function is important for fetal growth and neurological development.
TSH (at the very least) should be tested in the following circumstances:
A history of hypothyroidism/hyperthyroidism or current symptoms/signs of thyroid dysfunction
Known thyroid antibody positivity or presence of a goiter
History of head or neck radiation or prior thyroid surgery
Age >30 years
Type 1 diabetes or other autoimmune disorders
History of pregnancy loss, preterm delivery, or infertility
More than 2 prior pregnancies
Family history of autoimmune thyroid disease or thyroid dysfunction
Morbid obesity (BMI ≥40 kg/m2)
Use of amiodarone/lithium, or recent administration of iodinated radiologic contrast
Residing in an area of known moderate to severe iodine insufficiency
HbA1c
HbA1c refers to glycated hemoglobin, and provides a snapshot of plasma glucose levels over a 8 to 12 week period.
Screening is valuable in identifying women at higher risk of pregnancy complications and in detecting pre-existing diabetes. It is often used in conjunction with other screening methods to provide a comprehensive assessment of glucose metabolism during pregnancy.
This is not an alternative for gestational diabetes screening.
Vitamin B12
Vitamin B12 should be screened for in pregnancy as many people following vegetarian and vegan diets are typically low in Vitamin B12. This is important because adequate Vitamin B12 levels are necessary for proper fetal development, particularly with neural tube formation.
Vitamin D
Vitamin D testing in pregnancy is important because low levels are associated with increases in preterm birth and preeclampsia. Furthermore, women with a Vitamin D deficiency may experience more body pain and insomnia during pregnancy. In the postpartum, low levels of Vitamin D is associated with an increased risk of postpartum depression.
Final Notes
As you can see, first trimester blood work is an important component of prenatal care as it lays the foundation for a healthy pregnancy. By assessing a variety of factors such as hormone levels, vitamin deficiencies, and potential infections, a family doctor or obstetrical care provider can identify risks that may affect both the mother and fetus. Early detection allows for timely interventions, better management of potential complications, and ultimately promotes healthier outcomes for both mom and baby.