When Is a Woman Most Likely to Become Pregnant?

Basal Body Temperature

• A woman's body temperature undergoes a thermal shift once the lutenizing hormone (LH) is produced. This hormone causes the body temperature to rise, and the progesterone from the corpus luteum cyst keeps the temperature elevated unless implantation of an embryo occurs. If this does not occur, the corpus luteum shrinks and progesterone production stops, causing a drop in temperature again shortly before the onset of the menstrual period.

  To track body temperature, a sensitive thermometer called a basal body temperature thermometer is used. The temperature should be taken every morning at the same time, upon waking and before getting out of bed. The temperatures can then be recorded on a chart. When the temperature rises, ovulation is imminent, and the woman is approaching her most fertile time.

Ovulation Predictor Kits

• Another way of predicting ovulation is through the use of an ovulation predictor kit. Similar to a pregnancy test, an ovulation predictor detects hormones in the urine. The hormone this kit detects is the LH. The appearance of LH is the signal for the ovary to release the mature egg; when a woman sees a surge in her LH level, she is at her most fertile.

Cervix Position and Mucus

• The position of the cervix changes throughout a woman's cycle, as does the texture and quantity of her cervical mucus. At the start of her cycle, the cervix will be closed, low and firm in texture. As the cycle progresses, the cervix rises, the opening expands and the texture becomes soft. This is to aid the sperm in passing through the opening into the uterus. Checking the cervical position throughout the cycle will show when a woman is preparing to ovulate and become fertile.

  Cervical mucus also plays a role in conception, as it can keep sperm at the ready for up to three days while waiting for the egg to be released. At the beginning of the cycle, mucus will be dry, progress to thick and creamy, and finally become clear, abundant and stretchy. This is the most fertile cervical mucus and is known as "egg white cervical mucus" for the similarity in texture and appearance to the white of a chicken egg. As the cycle ends, the mucus reverts to creamy, then dry as the menstrual period begins.

  A woman is most likely to become pregnant when she has an abundance of egg white cervical mucus and her cervix is at the highest, most open position. This typically occurs midway through her menstrual cycle.