Q: Are there any studies on Egg-White Cervical Mucus and fertility?

A: Seven hundred twenty-five women of proven fertility recorded the presence of cervical mucus at the vulva in 7514 menstrual cycles. The mean cycle length of the 6472 "normal" cycles was 28.5 days (standard deviation +/- 3.18). The peak day of mucus discharge was the last day of slippery, raw-egg-white-like mucus and occurred on average on day 15 (+/- 2.6). The fertile period was defined as any day on which mucus was reported before the peak day until 3 days after the peak. Its mean length was 9.6 (+/- 2.6) days. The probability of pregnancy was maximal on the peak day and declined on the days before and after the peak.

Fertil Steril 1983 Dec;40(6):773-8
A prospective multicentre trial of the ovulation method of natural
family planning. III. Characteristics of the menstrual cycle and of the
fertile phase.