Latent class modeling of markers of day-specific fertility
- PDF / 484,031 Bytes
- 14 Pages / 439.37 x 666.142 pts Page_size
- 19 Downloads / 177 Views
Latent class modeling of markers of day-specific fertility Francesca Bassi1 · Bruno Scarpa1
Received: 28 November 2014 / Accepted: 24 May 2015 © Sapienza Università di Roma 2015
Abstract There is a considerable interest in predicting the fertile days in a woman’s menstrual cycles in couples desiring a pregnancy and among those wishing to avoid conception by periodic abstinence. Cervical mucus detection is potentially an accurate marker of fertile days. It is therefore of great interest to assess the magnitude of heterogeneity among women and among cycles and among cycles of a given woman, in the evolution in time of the mucus secretions detected during an interval of potential fertility and defined relative to ovulation. In this paper, we study the problem of heterogeneity in cervical mucus hydration at various times relative to the mucus peak, both among cycles and among women, specifying and estimating appropriate multilevel latent class models for longitudinal data. Results showed that heterogeneity in mucus evolution among cycles and women is non-negligible. Model estimates identified different mucus patterns for groups of cycles and women, and the characteristics of the cycles and the women which influence mucus symptom evolution over time. Keywords Menstrual cycles · Cervical mucus · Peak day · Multilevel latent class models · Multilevel latent growth mixture models
1 Introduction Observation of the cervical mucus symptom (CMS) is a widely used indicator to identify ovulation and the fertile phase in a menstrual cycle [3]. The CMS allows a woman to pinpoint the beginning of this phase, and it provides information on ovulation because cervical mucus secretions, stimulated by a rise in estrogen, are known to increase in volume 5–6 days prior to ovulation [17,20]. Ovulation is the key event in a menstrual cycle, determining the fertile interval during which intercourse can potentially result in pregnancy. However, women typically do not know when they ovulate, the day of ovulation may be detected retrospectively
B 1
Francesca Bassi [email protected] Statistics Department, University of Padova, Padua, Italy
123
F. Bassi, B. Scarpa
by observing how mucus characteristics evolve during cycle days [16,30]. The mucus peak day is considered to be the last day in the cycle, during which at least one characteristic of high fertility in mucus type has been observed or felt. This day must also be preceded by a sufficient increase in the feeling and appearance of mucus of more fertile propensity, which should later show a clear-cut change to less fertile [12]. Ovulation is expected within 2 days after the peak. The width of the fertile window around ovulation, i.e., the number of days during which intercourse has a non-zero probability of resulting in conception is uncertain, ranging in the reference literature from two to 10 days. However, some studies have shown that the probability of a pregnancy resulting from a single act of intercourse is small, unless intercourse occurs in the interval starting 5 days
Data Loading...
