Time to conception and the menstrual cycle: an observational study of fertility app users who conceived

Abstract

The objective of this research was to evaluate the association between menstrual cycle characteristics (cycle length, cycle-length variability, and their interaction) and the amount of time it takes women to conceive using a robust multiple linear regression. Participants downloaded Ovia Fertility in 2015 indicated that they had just started trying to conceive, and reported conception within 12 months (n = 45,360, adjusted model n = 8835). The average time to conception among women in the adjusted model was 3.94 months (n = 8835). Women with normal cycle lengths (27–29 days) conceived more quickly than women with cycle lengths of 25–26 days (+0.41 months; p < 0.001), 30–31 days (+0.27 months; p < 0.01), 32–33 days (+0.44 months; p < 0.001), and 34+ days (+0.75 months; p < 0.001). Women with regular cycle-length variability (<9 days between cycles) conceived more quickly than women with irregular variability (+0.72 months; p < 0.001). Results of the interaction analysis indicated that, among women with regular cycle-length variability, those with normal cycle length had shorter time to conception than women with either short or long cycle length. The interaction between cycle length and cycle-length variability provided enhanced insights into the amount of time it takes to conceive, compared to either indicator alone.

Keywords:

• Irregular
• variability
• menstrual cycle
• time to conception
• trying to conceive

Acknowledgements

The authors are grateful to Dr Alan Penzias, of Beth Israel Deaconess Medical Center (Boston, MA) and Dr Alexander Quaas, of the University Hospital Basel (Basel, Switzerland) for their editorial advice and review of the manuscript and analysis methodologies. The authors are also grateful to Ovia Fertility users for using the app and providing the data analyzed in this research. This research was funded by Ovia Health through the employment of four authors.

Disclosure statement

No potential conflict of interest was reported by the authors.