The carat (ct) is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls. The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.
Depending on your cycle length the most fertile days in the cycle varies: If you have 28 days between periods ovulation typically happens on day 14, and the most fertile days are days 12, 13, and 14. If you have longer cycles, say 35 days between periods, ovulation happens on day 21 and the most fertile days are days 19, 20, and 21.
All of the women were using an intrauterine device or had had a tubal ligation to protect against pregnancy. Previous research has shown that the five days leading up to ovulation and the day of ovulation are the days in a woman's menstrual cycle when she is most fertile. Increasing the frequency of sexual intercourse during these days increases the chance of pregnancy.