Normal Free and Total Testosterone in First Trimester Pregnancy
The available clinical guidelines do not establish reference ranges for free or total testosterone during the first trimester of pregnancy, as testosterone measurement is not part of routine prenatal assessment or screening protocols.
Why Testosterone Is Not Routinely Measured in First Trimester
The major obstetric and radiology guidelines focus on pregnancy-specific hormones rather than androgens for first-trimester evaluation:
- hCG (human chorionic gonadotropin) is the primary hormone measured, with pregnancy confirmed when serum hCG exceeds 5 mIU/mL 1
- Progesterone serves as a prognostic marker in some clinical contexts, though guidelines recommend against using progesterone supplementation based solely on serum levels in asymptomatic women 2
- First-trimester biochemical screening includes pregnancy-associated plasma protein A (PAPP-A) and free beta-hCG or intact hCG for aneuploidy screening between 11-13 weeks, but not testosterone 1
Research-Derived Reference Values
While not guideline-endorsed, research studies provide some data on testosterone levels during early pregnancy:
Total Testosterone
- First trimester levels in women carrying male fetuses: approximately 2.44 nM/L (70.4 ng/dL) based on a study measuring testosterone with highly specific RIA after chromatographic purification 3
- First trimester levels show elevation compared to non-pregnant values, with free testosterone remaining within normal limits in non-hirsute pregnant women 4
- One study identified 0.45 ng/mL (45 ng/dL) as a threshold associated with subsequent gestational diabetes development, though with poor sensitivity (63.6%) and specificity (62.7%) 5
Free Testosterone
- Free testosterone values increased in the first and third trimesters but remained within normal limits in all non-hirsute groups in one comparative study 4
- Amniotic fluid rather than maternal serum appears to be the best source for investigating fetal androgen exposure effects, as sex differences in testosterone are detectable in amniotic fluid but not maternal serum during the second trimester 6
Clinical Context and Limitations
Important caveats when interpreting these research values:
- Different assay methods produce varying results; liquid chromatography tandem mass spectrometry (LC-MS/MS) shows better correlation across platforms than analog RIA methods 7
- Maternal testosterone levels are influenced by fetal sex, with levels gradually increasing throughout pregnancy in women carrying male fetuses but decreasing after the first trimester in women carrying female fetuses 3
- The free-androgen index and calculated free testosterone may be more diagnostically useful than total testosterone in conditions affecting sex-hormone-binding globulin 4
- No clinical indication exists for routine testosterone measurement in uncomplicated first-trimester pregnancy based on current obstetric guidelines 1, 2
When Testosterone Measurement Might Be Considered
Testosterone assessment in early pregnancy is not part of standard prenatal care but might be obtained in specific clinical scenarios:
- Evaluation of hyperandrogenism or virilization symptoms
- Research protocols investigating gestational diabetes risk factors 5
- Investigation of disorders of sexual development when fetal sex discordance is suspected 6
The absence of established reference ranges in clinical guidelines reflects that testosterone measurement does not inform routine first-trimester pregnancy management, unlike hCG, progesterone, or aneuploidy screening markers 1, 2.