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.