Pregnancy

Preparing for Pregnancy: Essential Health Checks Before You Conceive

The Pin Health Staff Writer

January 21, 2026 11 min read

The best time to optimize your health for pregnancy is before you conceive. Here are the blood tests that can reveal hidden issues — and give your baby the healthiest start.

When you decide to have a baby, you start thinking about nursery colors, baby names, and prenatal vitamins. But there’s something more important to consider first: your own health.

Many health conditions that affect pregnancy outcomes are silent. You can feel perfectly fine while harboring thyroid dysfunction, nutrient deficiencies, or metabolic issues that impact fertility and fetal development. By the time you’re pregnant, some of these issues are harder to address — and the most critical period of fetal development happens in the first weeks, often before you even know you’re pregnant.

This is why preconception health matters so much. The months before pregnancy are your opportunity to identify and correct problems, optimize your nutrient stores, and create the healthiest possible environment for conception and early development.

A preconception checkup should go beyond “are you healthy enough to get pregnant?” It should ask: “Is your body optimally prepared to support a pregnancy and a developing baby?”

Blood testing can answer questions you didn’t know to ask — revealing hidden issues that affect fertility, pregnancy outcomes, and your baby’s long-term health.

Thyroid Function: The Fertility and Development Connection

Your thyroid gland plays a critical role in fertility, pregnancy maintenance, and fetal brain development. Both underactive thyroid (hypothyroidism) and overactive thyroid (hyperthyroidism) can cause problems.

Why it matters before and during pregnancy:

For fertility:

• Thyroid dysfunction can cause irregular ovulation or anovulation
• Even subclinical hypothyroidism (mildly elevated TSH) is associated with reduced fertility
• Thyroid issues can contribute to unexplained infertility

For pregnancy:

• Untreated hypothyroidism increases risk of miscarriage
• Associated with preterm birth and low birth weight
• Severe deficiency can affect fetal brain development
• Pregnancy increases thyroid hormone requirements — existing issues can worsen

The critical timing: Fetal brain development depends on maternal thyroid hormone in the first trimester, before the baby’s own thyroid is functional. This is why thyroid status should be optimized before conception, not discovered after.

What to test:

TSH is the primary screening test. Free T4 shows actual hormone levels. TPO antibodies can identify autoimmune thyroid disease (Hashimoto’s), which is common in women of reproductive age and associated with increased miscarriage risk even when TSH is normal.

If you have a history of thyroid problems, family history, or symptoms suggestive of thyroid dysfunction, comprehensive testing is especially important.

Iron and Ferritin: Building Reserves

Iron requirements increase dramatically during pregnancy — your blood volume expands by nearly 50%, and you’re supplying iron for fetal development and placental growth. If you enter pregnancy with depleted iron stores, you may not be able to keep up with demand.

Why it matters:

• Iron deficiency anemia during pregnancy is associated with preterm birth, low birth weight, and maternal complications
• Severe deficiency affects fetal brain development
• Many women are already iron deficient before pregnancy (especially those with heavy periods)
• Building iron stores takes time — you can’t rapidly correct deficiency once pregnant

What to test:

Ferritin reflects your iron stores — it’s the most important marker for preconception assessment. You can have normal hemoglobin while your ferritin is low, meaning you’re not anemic yet but your reserves are depleted. Serum iron, TIBC, and transferrin saturation complete the picture.

Ideally, ferritin should be well within the normal range before conception — not just “not deficient.”

Vitamin D: Beyond Bones

Vitamin D deficiency is extremely common — affecting over 40% of adults — and has significant implications for pregnancy.

Why it matters:

• Vitamin D deficiency is associated with reduced fertility
• Linked to increased risk of gestational diabetes
• Associated with preeclampsia risk
• May affect fetal bone development and immune function
• Deficiency during pregnancy is associated with childhood health issues

The repletion timeline:

If you’re deficient, it takes weeks to months of supplementation to reach optimal levels. Starting supplementation after you’re already pregnant means the critical early weeks occur while you’re still deficient. Testing and correcting before conception gives you time to optimize.

Folate and B12: Preventing Neural Tube Defects

The importance of folate (vitamin B9) for preventing neural tube defects is well established — it’s why folic acid supplementation is universally recommended before and during early pregnancy. But there’s more to the story.

Why folate matters:

• Neural tube defects (like spina bifida) develop in the first 28 days after conception — often before a woman knows she’s pregnant
• Adequate folate must be present before conception
• Some women have genetic variants (MTHFR) that affect folate metabolism and may need different forms of supplementation

Why B12 matters:

Vitamin B12 works closely with folate. Deficiency is common, especially in vegetarians and vegans. Low B12 during pregnancy is associated with:

• Increased risk of neural tube defects (independent of folate status)
• Preterm birth
• Low birth weight
• Developmental issues

B12 deficiency can also cause fertility problems, including anovulation and implantation failure.

The testing advantage:

Rather than just taking a standard prenatal vitamin and hoping for the best, testing shows your actual levels. Some women need higher doses. Some need specific forms. Some are deficient despite supplementation due to absorption issues.

Blood Sugar and Insulin: Metabolic Health Matters

Metabolic health before pregnancy influences both your ability to conceive and your pregnancy outcomes. Insulin resistance, prediabetes, and undiagnosed type 2 diabetes all increase risks.

Why it matters for fertility:

• Insulin resistance is strongly linked to ovulatory dysfunction
• PCOS, a leading cause of infertility, is characterized by insulin resistance
• High insulin levels disrupt hormonal balance needed for conception

Why it matters for pregnancy:

• Pre-existing diabetes or prediabetes significantly increases risk of birth defects if not well-controlled at conception
• Increases risk of miscarriage
• Higher likelihood of developing gestational diabetes
• Associated with macrosomia (large babies) and delivery complications
• Impacts long-term health of the child

What to test:

Fasting glucose and HbA1c assess blood sugar control. Fasting insulin can reveal insulin resistance before glucose becomes abnormal — this is especially important for women with PCOS or a family history of diabetes.

If metabolic issues are identified, addressing them before conception dramatically improves outcomes.

Complete Blood Count: The Basics Matter

A complete blood count (CBC) provides fundamental information about your blood health before pregnancy.

What it reveals:

• Hemoglobin and hematocrit — identify anemia
• MCV — helps differentiate types of anemia (iron deficiency vs B12/folate deficiency)
• White blood cells — general immune status
• Platelets — important for clotting

Anemia should be identified and treated before pregnancy, not during. And the type of anemia matters for treatment — iron deficiency anemia is treated differently than B12 deficiency anemia.

Rubella and Varicella Immunity

While not traditional “blood biomarkers,” immunity status for certain infections is crucial before pregnancy:

Rubella (German measles): Infection during pregnancy, especially in the first trimester, can cause severe birth defects. Most adults were vaccinated as children, but immunity can wane. A blood test confirms immunity. If you’re not immune, vaccination is recommended — but you must wait at least one month before conceiving after vaccination.

Varicella (chickenpox): Similar concerns. Chickenpox during pregnancy can cause serious complications. Immunity should be confirmed before conception.

Additional Considerations

Sexually Transmitted Infections

Certain STIs can affect fertility and pregnancy outcomes. HIV, hepatitis B, syphilis, chlamydia, and gonorrhea screening is recommended before conception. Some infections are treatable; others require management to prevent transmission to the baby.

Genetic Carrier Screening

Carrier screening can identify if you and your partner carry genes for certain inherited conditions (cystic fibrosis, sickle cell disease, Tay-Sachs, and others). This doesn’t require blood biomarker testing in the traditional sense but is an important preconception consideration.

Chronic Conditions

If you have any chronic condition — autoimmune disease, hypertension, epilepsy, mental health conditions — preconception planning with your healthcare provider is essential. Medications may need adjustment. Disease should be well-controlled before conception.

The Partner’s Health

Preconception health isn’t just about the person who will be pregnant. The male partner’s health affects fertility and potentially fetal development:

• Sperm quality is affected by overall health, nutrient status, and lifestyle factors
• Testosterone and other hormones influence fertility
• Oxidative stress and inflammation can damage sperm
• Certain nutrient deficiencies (zinc, folate, B12) affect sperm quality

While less is known about paternal preconception health compared to maternal, optimizing the health of both partners makes sense.

Timing: When to Test

Ideally, preconception testing should happen 3-6 months before you start trying to conceive. This allows time to:

• Get results and identify any issues
• Correct deficiencies (iron and vitamin D repletion takes weeks to months)
• Optimize thyroid function if needed
• Address metabolic issues
• Update vaccinations if necessary (and wait the required interval)
• Make lifestyle modifications

If you’re already trying to conceive, testing is still valuable — better late than never. But earlier is better.

Beyond Testing: Preconception Basics

Blood testing reveals what’s happening inside, but preconception health also involves:

• Prenatal vitamins: Start at least one month before conception (ideally three months), with adequate folate/folic acid
• Alcohol: No amount is proven safe during pregnancy; consider stopping when you start trying
• Smoking: Affects fertility and pregnancy outcomes; quit before conception
• Medications: Review all medications with your healthcare provider; some are not safe during pregnancy
• Weight: Both underweight and overweight can affect fertility and pregnancy outcomes
• Dental health: Gum disease is associated with pregnancy complications; address dental issues beforehand

The Bottom Line

Pregnancy is one of the most demanding physiological states your body will ever experience. It draws on your nutrient reserves, challenges your metabolic systems, and depends on proper hormone function. Starting from a position of optimal health gives you and your baby the best chance.

Many of the factors that affect fertility and pregnancy outcomes are invisible — you can’t feel your ferritin level dropping or your thyroid antibodies rising. Blood testing reveals what’s actually happening, allowing you to address issues before they become problems.

The best time to prepare for pregnancy is before you’re pregnant. Test, optimize, then conceive — with confidence that you’ve given your baby the healthiest possible start.

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Key Takeaways

• Preconception health affects fertility, pregnancy outcomes, and your baby’s long-term health
• Thyroid dysfunction is common in women — and affects both fertility and fetal brain development
• Iron stores should be optimized before pregnancy — demand increases dramatically, and repletion takes time
• Over 40% of women are vitamin D deficient — linked to fertility issues and pregnancy complications
• Folate and B12 are critical for neural tube development — which happens before most women know they’re pregnant
• Metabolic health impacts fertility and pregnancy — insulin resistance and prediabetes increase risks
• Testing should happen 3-6 months before conception — allowing time to correct any issues
• Both partners’ health matters — though maternal health has more direct impact