Time to Pregnancy for Women Using a Fertility Awareness Based Mobile Application  to Plan a Pregnancy

Carlotta Favaro; Jack T Pearson; Simon P Rowland; Anne Marie Jukic; Magda Chelstowska; Elina Berglund Scherwitzl; Raoul Scherwitzl; Kristina Gemzell Danielsson; Joyce Harper

doi:10.1089/jwh.2021.0026

Time to Pregnancy for Women Using a Fertility Awareness Based Mobile Application to Plan a Pregnancy

Favaro C, Pearson JT, Rowland SP, Jukic AM, Chelstowska M, Berglund Scherwitzl E, Scherwitzl R, Gemzell Danielsson K, Harper J

Published November 2021 Journal of Women's Health (2002), 30(11), 1538-1545

DOI 10.1089/jwh.2021.0026 PMID 34495761 PMC PMC8917888

RRM Academy Synopsis

Fertility app users got pregnant in a median of 4 cycles

In an observational cohort of 5,376 app users planning a pregnancy, about 6 out of 10 women got pregnant within 6 cycles. The median time to pregnancy was 4 cycles. Women under 35 with regular cycles who logged intercourse on at least 20% of days had the best chance of pregnancy each cycle.

Key Findings

Among 5,376 women, the 6-cycle cumulative pregnancy probability was 61% (95% CI: 59–62) and the 12-cycle probability was 74% (95% CI: 73–76).
The median time to pregnancy was 4 cycles, read from the Kaplan–Meier curve.
Among 613 women (11.5%) under 35 with cycle length variation <5 days and intercourse logged on at least 20% of days, 6-cycle probability was 88% (95% CI: 85–91).
Women over 35 had 6-cycle and 12-cycle probabilities of 54% (95% CI: 51–57) and 75% (95% CI: 73–78). Women with irregular cycles had 58% (95% CI: 55–62) and 79% (95% CI: 76–82).
Fecundability odds ratios fell below 1 for age over 35, underweight BMI, irregular cycles, and sporadic sexual activity, indicating worse fecundability.

Interpretation

This cohort study followed 5,376 Natural Cycles app users who were trying to conceive. Fecundability was lower with age over 35, underweight BMI, irregular cycles, and sporadic sexual activity, each linked with a longer time to pregnancy. The authors note that women who go on to conceive without the app are underrepresented in this kind of cohort. The findings support larger studies of cycle-tracking apps and conception timing.

RRM Context

Natural Cycles is one fertility awareness-based method. The authors cite Dunson et al. (1999), who found the conception rate highest when intercourse occurred on the day before ovulation. Restorative reproductive medicine treats a long time to pregnancy, or irregular cycles, as a reason to look for the cause. The authors suggest future algorithms may help identify couples who could benefit from infertility assessment.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

Time to pregnancy (TTP) is a biomarker of fecundability and has been associated with behavioral and environmental characteristics; however, these associations have not been examined in a large population-based sample of application (app) users.

Materials and Methods

This observational study followed 5,376 women with an age range of 18 to 45 years who used an app to identify their fertile window. We included women who started trying to conceive between September 30, 2017 and August 31, 2018. TTP was calculated as the number of menstrual cycles from when the user switched to "Plan" mode up to and including the cycle in which they logged a positive pregnancy test. We examined associations with several characteristics, including age, gravidity, body mass index, cycle length and cycle length variation, frequency of sexual intercourse, and temperature measuring frequency. Discrete time fecundability models were used to estimate fecundability odds ratios.

Results

For the complete cohort the 6-cycle and 12-cycle cumulative pregnancy probabilities were found to be 61% (95% confidence interval [CI]: 59-62) and 74% (95% CI: 73-76), respectively. The median TTP was four cycles. The highest fecundability was associated with an age of less than 35 years, with cycle length variation <5 days and logging sexual intercourse on at least 20% of days added (the proportion of days in which intercourse was logged) (11.5% [n = 613] of entire sample). This group achieved a 6- and 12-cycle cumulative pregnancy probability of 88% (95% CI: 85-91) and 95% (95% CI: 94-97), respectively, and a TTP of 2 cycles.

Conclusions

Natural Cycles was an effective method of identifying the fertile window and a noninvasive educational option for women planning a pregnancy. Women under age 35 with regular cycles showed a high pregnancy rate.

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Fertility Awareness Methods Compared

Topics

Fertility Awareness › Effectiveness › Fertile Window Estimation · Menstrual Cycle › Cycle Biomarkers › Basal Body Temperature

Carlotta Favaro, Jack T Pearson, Simon P Rowland, Anne Marie Jukic, Magda Chelstowska, Elina Berglund Scherwitzl, Raoul Scherwitzl, Kristina Gemzell Danielsson, Joyce Harper

C Favaro, John Pearson, J Pearson, S Rowland, A Jukic, M Chelstowska, E Scherwitzl, R Scherwitzl, K Danielsson, J Harper

PMID 34495761 34495761 DOI 10.1089/jwh.2021.0026 10.1089/jwh.2021.0026 Favaro et al. 2021, Favaro 2021