During which phase of the menstrual cycle does mittelschmerz occur?

Mittelschmerz Occurs During the Ovulatory Phase

Mittelschmerz occurs at mid-cycle during ovulation, when the follicle ruptures to release the egg. This typically happens approximately 14 days before the next menstrual period in women with regular cycles 1, 2.

Physiological Basis and Timing

The term "mittelschmerz" literally means "middle pain" in German, reflecting its occurrence at the midpoint of the menstrual cycle 2, 3. This pain coincides with:

• The ovulatory phase, which follows a sharp increase in luteinizing hormone (LH), estrogen, and follicle-stimulating hormone (FSH) levels during the late follicular phase 1
• The actual rupture of the ovarian follicle to release the mature egg 2
• The transition point between the follicular phase and luteal phase of the menstrual cycle 1

Clinical Characteristics

Mittelschmerz represents a normal physiological aspect of the menstrual cycle rather than a pathological condition 3. Key features include:

• Unilateral lower abdominal or pelvic pain that may alternate sides from cycle to cycle 2
• Brief duration, typically lasting from a few minutes to 48 hours 3
• Associated with free fluid in the pelvis on ultrasound examination in approximately 40% of normal cycles, with two-thirds of painful cycles showing ultrasonically demonstrated fluid at ovulation 2

Hormonal Context

During the ovulatory phase when mittelschmerz occurs, the hormonal milieu is characterized by:

• Peak estradiol levels with a sustained mid-cycle increase 1
• Low progesterone levels (progesterone rises after ovulation during the luteal phase) 1
• LH surge that triggers ovulation 1

This hormonal pattern is distinct from both the early follicular phase (when both estrogen and progesterone are low) and the mid-luteal phase (when both hormones are elevated) 1.

Clinical Significance

Mittelschmerz is considered a benign, self-limiting condition that reflects the physiological trauma of ovulation 2. It should be distinguished from other causes of cyclic pelvic pain such as:

• Primary dysmenorrhea, which occurs during menstruation rather than at mid-cycle 3
• Premenstrual syndrome, which occurs in the late luteal phase before menstruation 3
• Endometriosis-related pain, which may be cyclic but typically worsens during menstruation 3

The predictable mid-cycle timing and brief duration help differentiate mittelschmerz from pathological causes of pelvic pain 3.