Day 3 Fertility Testing: A Clinical Breakdown of Your Baseline Bloodwork and Ultrasound

Before any fertility treatment can begin, we need a precise, clinical baseline of your reproductive function. The foundational step of this diagnostic workup is known as “Day 3 Testing.” Scheduled between the second and fourth day of your menstrual cycle, this appointment provides a critical snapshot of your ovarian reserve and endocrine function.

We test on Day 3 because this is the early follicular phase. During this window, the communication loop between your brain and your ovaries is at its quietest, meaning your reproductive hormones should be at their starting baseline levels. Here is the clinical breakdown of exactly what we evaluate during this appointment.

The Baseline Transvaginal Ultrasound

A critical component of Day 3 testing is the transvaginal ultrasound. At this early stage in your cycle, we are looking for a completely “quiet” pelvis. We clinically evaluate several primary areas:

• The Antral Follicle Count (AFC): Using ultrasound, we count the number of small, resting follicles (measuring 2 to 10 millimeters) present on both ovaries. These are called antral follicles, and each one houses an immature egg. The total count gives us a highly accurate, physical representation of your resting ovarian reserve. A low AFC (< 5) may indicate Diminished Ovarian Reserve (DOR), while a very high AFC is frequently correlated with Polycystic Ovary Syndrome (PCOS).
• Endometrial thickness and ovarian cysts: Your uterine lining (endometrium) should be thinned out at this stage (typically under 6 millimeters), having just been shed. We also check the ovaries to ensure there are no lingering, estrogen-producing cysts from a previous cycle that could interfere with fertility medications, or other cystic lesions such as hemorrhagic cysts or endometriosis-type cysts (endometriomata).
• Uterine fibroids or other pelvic pathology: We assess for the presence of possible fibroids (benign muscle cell lesions of the uterus), or other findings that could impact reproductive function, such as significant pelvic adhesions in which an ovary may be stuck up behind the uterine body.

The Endocrine Panel (Bloodwork)

Along with the ultrasound, we draw blood to evaluate your endocrine system. By measuring these specific hormones at their baseline, we can predict how your ovaries will respond to stimulation medications.

• Follicle-Stimulating Hormone (FSH): FSH is a hormone secreted by the pituitary gland in your brain. Its job is to signal the ovaries to recruit and grow a follicle. On Day 3, your baseline FSH should be low (ideally under 10 mIU/mL). If your FSH is elevated, it indicates that your brain has to work exceptionally hard to “shout” at your ovaries to get them to respond. Elevated baseline FSH is a primary clinical indicator of Diminished Ovarian Reserve.
• Estradiol (E2): Estradiol is the primary form of estrogen in your reproductive years. It is produced by the growing follicles inside your ovaries. On Day 3, before any significant follicular growth has occurred, your estradiol should be low (typically under 50 pg/mL). We test estradiol alongside FSH because a prematurely high estradiol level can artificially suppress your FSH, masking diminished ovarian reserve.
• Luteinizing Hormone (LH): Like FSH, LH is produced by the pituitary gland. While LH is most famous for surging mid-cycle to trigger ovulation, its baseline level on Day 3 is clinically significant. We look closely at the ratio between your LH and FSH. In a typical baseline panel, the ratio is about 1:1. If your LH is significantly higher than your FSH (a 2:1 or 3:1 ratio), it is a strong clinical marker for PCOS.
• Anti-Müllerian Hormone (AMH): In a way similar to FSH, AMH is also a very powerful predictor of ovarian reserve. This hormone is produced by the granulosa cells of your resting (antral) follicles, and generally reflects the overall health of your functional eggs. The hormone is age-related and naturally drops as women age through their reproductive years. In younger women, it tends to be the most accurate reflection of egg reserve, and low AMH levels, i.e., < 1.0 or 2.0, indicate an early drop in fertility that would warrant sooner and more advanced reproductive therapies.

Using the Data

The results of your Day 3 ultrasound and bloodwork provide objective, scientific metrics of your egg status. By analyzing your AFC, AMH, FSH, estradiol, and LH together, our clinical team can construct a highly tailored stimulation protocol, determining both the exact medication dosages and the best treatment plan needed to safely and optimally maximize your egg yield and fertility potential.