EARLY-PREG protocol: Preconception, longitudinal, bidirectional, and counterfactual cohort of women trying to conceive for maternal–embryonic molecular crosstalk characterisation during the first weeks after conception
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
STUDY QUESTIONS
Embryo‒maternal crosstalk involves intense and complex molecular exchange between the early embryo and the mother. This interaction begins after fertilisation but is poorly understood before implantation. EARLY-PREG is a preconception open cohort that aims to research the proteome signature of maternal–embryonic communication, interrogating a growing biorepository of maternal fluids and tissues collected during the first two weeks of a natural conception.
WHAT IS KNOWN ALREADY
To understand the mother-embryo communication in humans, in vivo , ex vivo , and in vitro biological models have been developed to simulate certain phases of the implantation process and its related events. Mass Spectrometry (MS) for proteomic profiling in longitudinal cohort studies has emerged as a modern method for understanding complex biological processes directly in vivo . Proteomic profiles have been investigated during pregnancy in women from the 8th week of gestation, but not before.
STUDY DESIGN, SIZE, DURATION
In three waves of recruitment from 2017 to 2024 so far, healthy women seeking to conceive have been recruited in Concepcion, Chile. Participants completed a survey with health, lifestyle, and sociodemographic data, their menstrual cycles with ovulation, and fertile window ascertainment (ultrasound, fertility monitor, and/or LH strips) were followed prospectively until pregnancy was achieved, or for a maximum of six consecutive cycles. The follow-up of every cycle included systematic day-by-day sampling of cervicovaginal fluid (CVF), urine, saliva, and blood. In addition, we collected a cervical brushing between days 12 th and 14 th post-ovulation. The day of ovulation and other time windows of interest in each cycle were retrospectively corrected by hormonal curves (LH, oestradiol, progesterone and beta-hCG) on stored blood and urine samples. Cervical brushings were collected on day 21 post-ovulation and in each trimester of pregnancy.
PARTICIPANTS, MATERIALS, SETTING, METHODS
At present, 1,183 women have been contacted, of whom 223 met all eligibility requirements; 129 participants who were trying to conceive completed the protocol for at least one complete cycle, of whom 35 participants achieved full-term pregnancies and 17 had early pregnancy losses; 40 abstinent and 5 sterilised women entered and completed the protocol. A total of 293 menstrual cycles have been fully documented and sampled; 53 have been classified as conception cycles and 240 as non-conception cycles; of the latter, 31 correspond to non-conception counterfactual cycles and 209 to non-counterfactual cycles. The biorepository encompasses maternal fluids and tissues collected throughout the first 2 weeks after ovulation for all 293 cycles to date. Biospecimen collection compliance has been high for most specimens. The cohort is currently supporting proteomic analyses of maternal fluids from women who conceived and their counterfactual non-conception cycles to characterise the proteome signature of early pregnancy. A fourth recruitment wave to characterise changes of the immunophenotype in maternal peripheral blood mononuclear cells (PBMC) during ultra-early pregnancy is planned to begin in 2025.
STUDY FUNDING/COMPETING INTEREST
The EARLY-PREG preconception open cohort has been supported by multiple research grants awarded by the FISAR Foundation ( www.fisarchile.org ). The pilot study and the first wave of recruitment were supported by grants #MEL109112011 and #MEL109112011R4 awarded to E.S.K., C.V. and J.F.S. The second wave of recruitment was supported by supplemental grants #MEL109112011R5 and #MEL131032017R1 awarded to E.S.K. The third wave was supported by grant #MEL205062018 awarded to E.S.K. and M.H. Current funding for the design of the fourth recruitment wave and MS research on maternal CVF is supported by grant No. REH042024-01 awarded to M.H., G.N., and E.S.K. As a senior scientist, E.S.K. has served as an honorary research consultant and/or reviewer on research applications for the FISAR Foundation since 2015. No other conflicts of interest are reported.
TRIAL REGISTRATION NUMBER
Not applicable.
TRIAL REGISTRATION DATE
Not applicable.
DATE OF FIRST PATIENT’S ENROLMENT
Not applicable.
