Endometrial thickness is not independent of luteal phase day in a rural Polish population

Abstract

The endometrium is important for luteal phase function, implantation, placentation, and gestation. Endometrial morphology has been shown to impact early pregnancy success in in vitro fertilization and egg donor cycles and has been implicated in conception success in spontaneous cycles. However, few studies have monitored endometrial morphology in normo-ovulatory women or examined possible population variation in its physiology or thickness. Further, the methodology of most studies of the endometrium is to take a single measurement close to ovulation, meaning the endometrium is not often measured during the window of implantation; the assumption has been that an individual's endometrial thickness (ET) is consistent through the luteal phase. Therefore, we have tested the hypothesis that ET is independent of luteal phase day in a study of urban-dwelling US and rural Polish women. We found that ET is not independent of luteal phase day in this sample of rural Polish women: ET is negatively associated with cycle day (P = 0.03). Compared to the US sample, the Polish sample also had a significantly later age at menarche (P = 0.002), lower midluteal progesterone concentrations (P = 0.0006), lower C-peptide concentrations (P = 0.0003), and higher energy expenditure (P = 0.03), suggesting greater energetic constraint. The relationship between ET and luteal phase length highlights the need to measure the endometrium serially over the menstrual cycle in order to better document inter-and intra-population variation in reproductive function.

Relationships between biomarkers of inflammation, ovarian steroids, and age at menarche in a rural polish sample

“…The timing of urine collection in the original study was to measure C‐peptide concentrations (Clancy et al, ), and designed to promote ease of collection for participants, and thus four consecutive early mid follicular days were sampled (days 3–6 from first day of menses), and three consecutive early mid luteal days (days 21–23). In designing this secondary analysis of urine samples for CRP, we hypothesized that these two time periods represented times of low inflammatory activity of reproductive origin, as menses would be nearly over and the implantation window not yet, or only just begun for most participants.…”

“…Younger women are able to recall their age at menarche with much greater accuracy (Koo and Rohan, ; Koprowski et al, ; Must et al, ) than women into middle age (Cooper et al, ). Because age at menarche is later in this sample than industrial population samples (Clancy et al, ), and participants were 20–40 years old, the time of recall was in the range of other studies that have shown good accuracy in recalled age at menarche.…”

The reproductive ecology of iron in women

“…While the causes of variation in human menstrual reabsorption have not been explicitly tested, several studies suggest which factors might control how much blood, and thus iron, a body loses during menstruation and how much it reabsorbs and reuses. For example, some evidence indicates that menstrual blood loss is sensitive to energetic condition (Clancy, ; Clancy et al, ; Rowe et al, ), although this has not yet been tested directly. The Polish population, Clancy et al () studied and the Kenyan population Miller () studied have a high physical workload; the Kenyan women also had poor nutritional status.…”

Declining ages at menarche in an agrarian rural region of Poland

“…Women (n = 1326) were recruited at the Mogielica Human Ecology Study Site in the Beskid Wyspowy region of southern Poland between 2003 and 2018. Details about the study site and recruiting procedures have been described elsewhere (Clancy et al, , ; Lee, Rogers, Galbarczyk, Jasienska, & Clancy, ; Puskarczyk et al, ). All women provided written informed consent.…”

“…Research was conducted in the mountainous Beskid Wyspowy region, where women historically grew up living and/or working on family farms and continuing to work on farms and large vegetable gardens into adulthood (Jasienska, ). Women in this region have later ages at menarche than the United States (Clancy, Ellison, Jasienska, & Bribiescas, ). While farming is still common, the region is transitioning toward a more labor‐based market (Colleran, Jasienska, Nenko, Galbarczyk, & Mace, ).…”