Planning pregnancy – does temperature help?

Is the temperature graph useful in planning pregnancy?

The Temperature (BBT) chart can give three pieces of information of use to the couple planning pregnancy:

  1. The Temperature Chart can confirm ovulation.
  2. The Temperature Chart can confirm ovulation did not occur.
  3. The Temperature Chart can confirm pregnancy (Fig. 12-3)

Temperature Chart (thermal shift) can confirm ovulation:

The rise in the basal body temperature (BBT) tells the woman that ovulation has occurred. Although this information is reassuring to the couple, from the point of view of achieving pregnancy it is of little use because once the thermal shift occurs the possibility of pregnancy decreases almost immediately as the ovum lives for just 24 hours and the fertilizable life of the ovum within that 24 hour period is from 8 to 12 hours.1

The cervical mucus indicator defines the fertile phase of the cycle before the thermal shift occurs. Therefore to achieve pregnancy sexual intercourse should occur on those potentially fertile days leading up to ovulation when oestrogenic fertile-type mucus is present and in which sperm can survive for up to five days.2

Temperature Chart can confirm ovulation did not occur in the cycle, (this is called an anovular cycle)

This information is also of use to the couple. Occasionally an anovular cycle may occur. However if anovular cycles are recurring the woman should consult her doctor. (see Fig 12-2 in What Information Can Be Got From The Temperature Graph?).

Temperature Chart can confirm pregnancy (Fig. 12-3)

Fig. 12-3; The temperature chart can confirm pregnancy: Day 1 of the cycle marked on the bottom of the chart is the first day of the period (marked B). On Day 16 there is a rise in temperature and it remains elevated until Day 40 which is the last day shown on this chart. A higher-phase temperature that persists for 21 days or more indicates pregnancy. There is a further rise in temperature at the time of implantation on Day 24 due to the increase in progesterone secretion from the corpus luteum. The embryo implanting in the endometrium starts secreting human chorionic gonadotrophic hormone (hCG) which prevents the demise of the corpus luteum.3 Progesterone from the corpus luteum supports the pregnancy for 8 weeks after conception after which the embryo is capable of synthesizing all steroid hormones required for its development.3,4  Ovulation occurred sometime between Day 15 and Day 16. (see Fig 6-17 in Factors Necessary To Achieve Pregnancy).

IMPORTANT: The RULES of the ‘symptothermal double-check method’ of natural family planning regarding thermal shift interpretation, must be taught to the woman by a trained natural family planning teacher.

References:

  1. World Health Organization: WHO Task force on methods for the determination of the fertile period; temporal relationship between ovulation and defined changes in the concentration of plasma estradiol-17b, LH, FSH, and progesterone. Special Programme of Research, Development and Training in Human Reproduction. Am J Obstet Gynecol 1980; 138:383-390B
  2. Klaus H; ‘Natural family planning – Is it scientific? Is it effective?’ page 4; Newman Lecture Series 1-May 21, 2000. (online)
  3. Manassiev Nikolai, Whitehead, Malcolm; ‘Female Reproductive Health’; 2004, ISBN 1-85070-491-0
  4. Griffin James E, Ojeda, Sergio R; ‘Textbook of Endocrine Physiology’;1996, p226-228; ISBN 0-19-510755-1(pbk)