Planning Pregnancy? Your Genes Hold Critical Health Information.

BRCA1 is a tumor suppressor gene that acts like your cells’ quality control system. Its job is to detect DNA damage and either repair it or trigger the cell to self-destruct if damage is too severe. Without functional BRCA1, mutations accumulate in your cells over time, eventually leading to cancer.

Pathogenic variants in BRCA1, carried by roughly 1 in 400 people in the general population, eliminate this protective function. Women with BRCA1 mutations face a 55-72% lifetime risk of developing breast cancer, often at younger ages than the general population average. Men with BRCA1 mutations face elevated prostate cancer risk and can pass the variant to their children.

For pregnancy planning, a positive BRCA1 status means you need earlier and more frequent breast cancer screening (possibly starting in your 20s), considerations about hormone-based contraception and hormone replacement therapy, and genetic counseling about your children’s 50% inheritance risk. The gene itself doesn’t cause pregnancy complications, but the knowledge changes your medical decisions for decades.

BRCA2 works alongside BRCA1 to repair double-strand DNA breaks, one of the most serious types of cellular damage. When BRCA2 is functional, cells catch and fix mistakes before they become cancers. When BRCA2 is mutated, this repair pathway fails.

BRCA2 mutations occur in roughly 1 in 800 people and carry a 45-69% lifetime breast cancer risk, plus elevated ovarian cancer (10-20% lifetime risk) and male breast cancer risk. Unlike BRCA1, BRCA2 mutations also significantly increase pancreatic and prostate cancer risk, even in women. The cancer typically emerges later than BRCA1-associated cancers but is equally serious.

During pregnancy and postpartum planning, BRCA2 status shapes decisions about screening, hormonal contraception (some variants counsel against estrogen-based birth control), pregnancy timing, and whether to pursue preventive surgery. Your children have a 50% chance of inheriting your variant. This gene is your signal to get genetic counseling before conception and to create a surveillance plan that lasts your entire life.

MTHFR is the enzyme that converts dietary folate and folic acid into methylfolate, the active form your cells actually use. This isn’t optional; methylfolate is essential for DNA synthesis, repair, and replication. It’s especially critical during pregnancy, when your baby’s cells are dividing thousands of times per second and the neural tube (which becomes the brain and spinal cord) is forming.

The C677T variant in MTHFR, carried by roughly 40% of people with European ancestry, reduces enzyme activity by 40-70%. If you have the C677T variant, your cells cannot convert standard folic acid into usable methylfolate as efficiently as other people, even if you’re taking prenatal vitamins. This is especially risky in the first trimester when neural tube closure happens. Homozygous carriers (two copies) are at higher risk; heterozygous carriers (one copy) have moderate reduction.

For pregnancy, an MTHFR variant means you need methylfolate supplementation specifically, not just standard folic acid. Standard prenatal vitamins contain folic acid, not methylfolate, so you’ll need to upgrade your supplement protocol. This is one of the few genetic findings where the intervention is simple and evidence-based: switch the form of B vitamin and reduce your baby’s neural tube defect risk.

Factor V is a clotting protein that helps your blood form protective clots when you’re injured. The body carefully balances clotting (necessary to stop bleeding) and clot breakdown (necessary to prevent clots from traveling where they shouldn’t). The F5 Leiden variant changes how quickly your body breaks down clots.

Factor V Leiden, carried by roughly 5% of people with European ancestry, increases venous thromboembolism (blood clot) risk 4-8 fold. During pregnancy, the risk jumps dramatically because pregnancy itself is a hypercoagulable state, meaning your blood naturally becomes more prone to clotting. Heterozygous carriers (one Leiden allele) face roughly 4-8x baseline clot risk; homozygous carriers face much higher risk. For women on hormonal contraceptives, the risk multiplies again to roughly 30-40x.

For pregnancy planning, F5 Leiden is one of the most actionable findings. If you carry the variant, you need to avoid hormonal contraceptives before pregnancy, be aware of increased clot risk during pregnancy and the postpartum period (especially the first 6 weeks after delivery), and discuss thromboprophylaxis (blood thinner medication) with your obstetrician. This gene alone can change your entire pregnancy management plan.

HBB produces the beta chain of hemoglobin, the protein in red blood cells that carries oxygen throughout your body. Variants in HBB cause some of the most common inherited blood disorders globally: sickle cell disease, beta-thalassemia major, and beta-thalassemia trait (carrier status).

If you carry one HBB variant, you’re a carrier with usually mild or no symptoms but a 25% chance per pregnancy of having a child with sickle cell disease or thalassemia major (if your partner also carries a variant). If you’re homozygous or compound heterozygous (carrying two different HBB variants), you have the actual disease, which affects oxygen transport throughout your body and causes chronic anemia, pain crises, and complications. Prevalence varies dramatically by ancestry; African ancestry, Mediterranean ancestry, and Middle Eastern ancestry populations have higher carrier frequencies.

For pregnancy, knowing your HBB status is essential for family planning. If you’re a carrier and your partner is also a carrier (many couples don’t know), genetic counseling and potentially prenatal testing or preimplantation genetic diagnosis become important options. If you have the disease itself, pregnancy planning requires specialized high-risk obstetric care. This gene determines whether carrier screening becomes a couple’s conversation before conception.

HLA-DQ2 is an immune system gene that produces a protein found on the surface of immune cells. In people with HLA-DQ2, the immune system can develop an abnormal response to gluten (a protein in wheat, barley, and rye), leading to celiac disease. The protein itself is neutral; it only becomes problematic if the immune system mounts an attack against gluten.

Roughly 30-40% of the general population carries HLA-DQ2, but only 3-5% of carriers ever develop celiac disease. This means HLA-DQ2 is necessary but not sufficient for celiac disease; you need both the gene and an environmental trigger (often gluten exposure, stress, or infection). If you carry HLA-DQ2, your risk of celiac disease is elevated, and if you have celiac disease, you almost certainly carry HLA-DQ2. Your children have a 50% chance of inheriting it from you.

For pregnancy, HLA-DQ2 matters because undiagnosed celiac disease during pregnancy increases miscarriage risk, causes nutritional deficiencies that affect fetal development, and reduces birth weight. If you carry the gene and have unexplained anemia, fatigue, or GI symptoms, celiac disease screening before or early in pregnancy is worthwhile. Knowing your status helps you advocate for serologic testing if you develop symptoms, and it informs your child’s risk profile.