Pregnancy blood tests results

The results of blood work during pregnancy are often a bit shocking to even the savviest of clinicians trained in blood chemistry analysis.

Why are tests so different in pregnancy and postpartum compared to other times of life?

And how do we accurately assess pregnancy blood tests? Results often seem pathological when, in reality, they’re completely normal!


This blog will explore these questions, as well as my unique journey in learning about this amazing time of life.

Pregnancy started my nutritional journey

I’ve now nutritionally supported preconception, pregnancy, and postpartum clients for over a decade. In fact, my decision to become a nutritionist stemmed from the amazing realizations I had after the birth of my (now 11-year-old!) son.

And while I love the foundational, food-first approach that I rely on for creating my clients’ recommendations, there is one aspect of my reproductive-focused work that becomes more enthralling to me as time passes—pregnancy blood tests. Results I never expected to see on a blood test gently and progressively catapulted me into what has grown into one of the most interesting research projects of my career.

It was around 2014 that I first noticed the differences in my pregnant and postpartum clients’ blood work versus other blood work I’d seen. When I would notice a test result that was outside of the range, I would look it up to investigate whether it was actually normal for their stage in the reproductive journey.

Initially, I used my copy of the Teitz Textbook of Clinical Chemistry and the (wonderful!) website to access reference ranges for my reproduction clients.

However, I quickly found that even these fantastic resources had their limits: Some of the ranges didn’t match what I was seeing in more recent hematological studies or reveal pathological patterns that indicated issues such as preeclampsia, gestational hypertension, or gestational diabetes.

Even though I was doing a lot of research to find the best way to interpret pregnancy blood tests, results reported by my clients made it totally worth it!


I felt committed to catching red flags to prevent a more serious health problem down the line if something was out of balance—for example, paying close attention to the neutrophil to lymphocyte ratio, alkaline phosphatase, and uric acid—while reassuring clients that a marker flagged as being outside of the non-pregnancy reference range might actually be normal.

Every time a client let go of a superfluous worry, and every time I caught a little something peculiar and fixed the issue before the client developed a more serious problem, I felt gratified.

I was able to relieve my clients’ anxiety, avoid further testing or support that wasn’t needed, and learn so much along the way.

Learning more by working together

My clinical work and research for pregnant and postpartum clients continued in this vein until last year.

I met MaryAnn Marks through a common acquaintance—I was told she was researching a new way to interpret blood tests and developing software to accompany her findings. I was immediately curious about her work.

I spoke with MaryAnn and was excited to see that not only was she researching the best way to analyze blood tests by trimester of pregnancy, but she was also researching optimal ranges according to a person’s age, sex, ethnicity, elevation, alcohol intake, and smoking status, along with menopausal status and where they were in their menstrual cycle!

I thought about my practice—I work with clients all over the world of different ages and ethnicities, living at different elevations…all factors that affected their test results and ranges.

I knew that the functional ranges I had learned were in many ways better than conventional ranges commonly used in the medical field, but the research MaryAnn showed me took this idea to another level.

We stayed in touch and began researching together. Our collaboration resulted in a growing list of incredible studies that led us to new and evidence-based ways to analyze blood tests in preconception, pregnancy, and postpartum.

What did we find?

pregnancy blood tests results

Pregnancy blood tests: Results according to trimester

First, we built on the knowledge that the ranges for many tests will shift according to trimester.

This was something I had observed in my practice, but it turned out to be the case for many markers.

On the complete blood count alone, we found evidence that

  • white blood cells
  • mean corpuscular volume
  • mean corpuscular hemoglobin
  • mean corpuscular hemoglobin concentration
  • red cell distribution width
  • platelet count
  • mean platelet volume
  • neutrophils
  • lymphocytes
  • monocytes

all need special pregnancy ranges and change as the trimesters progress.

Some tests, however, were more affected than others by physiological changes in the first trimester.


For instance, I commonly notice that thyroid markers dramatically shift in my pregnant clients. Initially, I was alarmed as pregnancy can often be a contributing trigger for thyroid autoimmunity or worsening of autoimmune symptoms for those who are diagnosed.

However, it is completely normal to see a decrease in TSH due to the actions of placental human chorionic gonadotropin (hCG) combined with an increase in thyroxine-binding globulin due to higher estrogen.

The mechanisms are amazing and complex!

Add to this the wide (but, again, normal) variation in thyroid markers between individuals.

For example, the conventional ranges for TSH are incredibly wide: 0.5-5.0 mIU/L. And while some research shows the most optimal range for non-pregnant people is approximately 1-2 mIU/L, my clinical experience and that of other wellness professionals show that sometimes healthy, well-functioning people have individual ranges that fall outside of those guidelines.

The key to accurate TSH interpretation, then, is to compare the person to the person versus the person to a set-in-stone range.

For instance, does your client have a consistent yearly TSH of 0.5 mIU/L with no signs of hyperthyroidism or pituitary/hypothalamic stress?

Is your client Black? Studies show that Black people may have slightly lower TSH levels when compared to White people, even after adjustment for age and sex (1).

Then this might be their normal, and that’s ok!

If this person becomes pregnant, their TSH may drop to an even lower value. And while they should be working with a licensed professional who can monitor their tests and symptoms, you can be armed with the knowledge that this drop is more than likely a normal variation due to physiological changes in the first trimester.

Pregnancy blood tests: Results won’t be accurate with functional ranges

I want to emphasize this point: Functional ranges won’t work in pregnancy, postpartum, and lactation.

Functional blood chemistry analysis is a fantastic tool that has taught me so much about physiology and how to better support my clients…but not my pregnant clients.

And while some experienced OBGYNs and midwives actively use pregnancy-specific ranges, no functional blood chemistry program currently teaches ranges for pregnant or postpartum women.

Yet tests on every section of a blood panel—CMP, lipids, CBC with differentials and iron markers, as well as thyroid markers, discussed above, will shift in pregnancy and postpartum, sometimes lasting well into lactation (2).

So what do you do? How can you support your pregnant patients with the most physiologically accurate ranges for them?


MaryAnn and I are collaborating to create comprehensive resources for blood test interpretation in the reproductive years. We’re publishing blogs, teaching free webinars, and even have plans to launch a 6-week course this summer!

We’d love to tell you about what we’re finding. Click here to sign up for our 6-week masterclass if you’d like to stay in touch and learn more.

And if you have any specific questions, email me at [email protected], and let me know!