Menstrual Cycle Length Correlated with Ovarian Reserve

Issue 02: 21 Jan 2008
Source: Fertility and Sterility 2008;in press
Mean menstrual cycle length is an age-independent predictor of success in assisted reproduction, according to new findings from a prospective study of more than 6,000 fertility treatment cycles.

Specialists from centers in Uppsala, Sweden, performed a study of 6,271 IVF/ICSI treatment cycles in 3,228 women in the period 1999-2005, to investigate the relationship between menstrual cycle length and assisted reproduction success rates.

Before starting treatment, the women provided a menstrual history of the previous year, enabling the researchers to estimate mean menstrual cycle length. Previous studies have indicated that women recall their menstrual history relatively well, and that there is a high concordance between prospectively recorded cycle lengths and those stated by women before recording. In the new study, cycles were excluded if there was any use of hormonal therapies.

The researchers found that increasing age was associated with a small but significant reduction in mean menstrual cycle length. The mean menstrual cycle length was 30 days in women aged 28 years or younger, decreasing to 28.1 days in women aged 40 years or older.

Mean menstrual cycle length was significantly correlated with pregnancy and delivery rates, and this correlation persisted after adjusting for age. Women who had a mean menstrual cycle length of more than 34 days had a delivery rate per embryo transfer that was almost double that of women who had a mean menstrual cycle length of less than 26 days.

Overall, the percentage of the study population in each category of menstrual cycle length, and their delivery rates, were as follows:

Mean menstrual cycle length less than 26 days: 7 percent of the study population; delivery rate per embryo transfer (ET) 16.9 percent.
26 or 27 days: 20.4 percent of population, delivery rate/ET 23.7 percent.
28 or 29 days: 46.5 percent of population, delivery rate/ET 25.3 percent.
30 or 31 days: 14.7 percent of population, delivery rate/ET 28.2 percent.
32, 33 or 34 days: 5.7 percent of population, delivery rate/ET 31.3 percent.
More than 34 days: 5.7 percent of population, delivery rate/ET 30.9 percent.
The researchers also found that mean menstrual cycle length was significantly correlated with ovarian response to FSH/hMG stimulation and with embryo quality.

Discussing their findings, the researchers note the implications of their findings for fertility counseling and family planning, pointing out: “Given the strong trends to delayed childbearing in Western society, often combined with an over-optimistic attitude to fertility at advanced reproductive age, [menstrual cycle length] may be used as an easily accessible screening for ovarian reserve.”

They say a shortened mean cycle length may indicate that a woman’s fertility is declining, and that a more thorough investigation of ovarian reserve should be performed: “If such an evaluation confirms a reduced ovarian reserve, she may choose to establish a family earlier than otherwise intended.”