Howard, M. P., & Stanford, J. B. (1999). Pregnancy probabilities during use of the Creighton Model Fertility Care System. Archives of Family Medicine, 8(5), 391-402. https://doi.org/10.1001/archfami.8.5.391
Howard MP, Stanford JB. Pregnancy probabilities during use of the Creighton Model Fertility Care System. Arch Fam Med. 1999;8(5):391-402. doi:10.1001/archfami.8.5.391
Howard, M. P., and J. B. Stanford. "Pregnancy probabilities during use of the Creighton Model Fertility Care System." Archives of Family Medicine, vol. 8, no. 5, 1999, pp. 391-402.
Creighton Model had 0.14 method-related pregnancies per 100 couples a year
The net probability of method-related pregnancy was 0.14 per 100 couples over 12 months of Creighton Model use, an observational cohort of 701 couples in Houston found. Achieving-related behavior accounted for 12.84 of the 17.12 total pregnancies per 100 couples. The authors define it as genital contact on a day known to be fertile.
Key Findings
With the Creighton Model Fertility Care System (CrMS), net 12-month pregnancy probabilities per 100 couples were 0.14 method-related, 2.72 from user and/or teacher error, and 1.43 unresolved.
Per 100 couples, the net total pregnancy probability was 17.12 after 12 months of follow-up and 21.26 after 18, and the gross total at 12 months was 22.78.
Across assumptions about unresolved pregnancies, avoiding-related pregnancy at 12 months ranged from 3.11 to 4.28 per 100 couples, and extended-use pregnancy from 18.47 to 22.51.
Net total probabilities at 12 months per 100 couples were 13.98 with uncomplicated regular cycles, 17.65 with long cycles, 18.40 after discontinuing oral contraceptives and 23.81 with breastfeeding.
The authors conclude that the CrMS compares favorably with other family planning methods on pregnancy probability and that women without regular cycles can use it successfully.
Interpretation
The observational cohort followed 701 couples for up to 18 months. They began the CrMS at a Houston natural family planning program between 1983 and 1989. Couples with a history of infertility were excluded. Essentially all other new users were enrolled, including women who were breastfeeding or had recently stopped oral contraceptives. Each pregnancy was classified after a detailed evaluation, and both net and gross life-table analysis were applied. The authors note that the total includes pregnancies that many other studies exclude as planned. They consider it likely that the most comparable figure for use-related pregnancy lies between the avoiding-related and extended-use estimates.
RRM Context
The CrMS is a cervical mucus-based method. Women chart their daily observations, and couples read the chart to find fertile and infertile days. The chart also records ovulatory function, so cycle charting informs restorative reproductive medicine. Couples with long cycles, recent oral contraceptive use or breastfeeding used the method in this cohort, which extends charting to varied reproductive circumstances.
Our editorial summary of this paper, not the article's abstract.
Abstract
Objective
To evaluate pregnancy probabilities during use of the Creighton Model Fertility Care System (CrMS).
Design
Couples who began use of the CrMS were entered into this observational cohort study. Follow-up included detailed reviews of use of the CrMS. Pregnancy probabilities were calculated with both net and gross life-table analysis through 18 months.
Setting
A natural family planning service delivery program based at an urban hospital in Houston, Tex.
Subjects
A group of 701 couples who received instruction in the CrMS were entered into the study. Most couples (93%) were engaged or married. Most women were white (83%), between the ages of 20 and 34 years (88%), and college graduates (58%).
Main Outcome Measures
Pregnancies were classified based on a detailed evaluation involving the pregnant woman (usually with her partner).
Results
At 12 months, the following net pregnancy probabilities were found per 100 couples: method-related pregnancies, 0.14; pregnancies caused by user and/or teacher error, 2.72; pregnancies caused by achieving-related behavior (genital contact during a time known to be fertile), 12.84; unresolved pregnancies, 1.43; and total pregnancies, 17.12. Pregnancy probabilities were similar when stratified by the following reproductive categories: uncomplicated regular cycles, long cycles, discontinuing oral contraceptives, breastfeeding, and other.
Conclusions
Pregnancy probabilities of the CrMS compare favorably with those of other methods of family planning. Most pregnancies result from genital contact during a known fertile time. Women need not have regular cycles to use the CrMS successfully.
Clinician-reviewed comparison of fertility awareness-based methods (Billings, Creighton, Sensiplan, Marquette, Standard Days, apps). Every effectiveness figure cited and labeled by metric.
NaProTechnology diagnoses and treats the underlying conditions driving infertility, menstrual disorders, and early pregnancy loss. This guide covers how the method works, published outcomes data, how to find a qualified provider, and what to expect on cost and insurance.
