Background:
Pre-eclampsia (PE) is a multisystemic syndrome occurring in 4-5% of pregnant women. It is
defined by a new-onset hypertension (HT) developing after 20 weeks of gestation in
combination with one of the following entities: proteinuria, maternal organ dysfunction
and/or uteroplacental insufficiency. The vicious circle of the syndrome can end up in
life-threatening complications for mother and child and, today, the only treatment of cure is
the induction of delivery. Furthermore, besides the problems in the acute phase of the
disease, women who experienced PE have been shown to have an increased lifetime risk of
developing cardiovascular disease (CVD) and chronic kidney disease, while the children carry
the consequences of their prematurity and, often following intra-uterine growth restriction,
also seem to be more prone to develop metabolic disturbances like diabetes, HT and CVD later
in life. Research, including data publishes by my own research group, shows that the risk of
PE development in subfertile patients undergoing assisted reproductive technology (ART), is
more than doubled, with incidences between 8-12%.
ART includes in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), using
autologous or heterologous gametes, followed by fresh or frozen embryo transfer. The
increased risk of PE within this population has mainly been attributed to known maternal PE
risk factors associated with ART like increased maternal age, nulliparity and metabolic
disturbances e.g. in patients with polycystic ovary syndrome (PCOS). Recent studies however
have shown that ART is an independent risk factor of PE. More specifically, a higher PE
incidence is consistently observed when patients have a frozen embryo transfer (FET) in an
artificially prepared cycle. Unlike in a natural cycle in which ovulation occurs, an
artificial cycle is characterized by the absence of ovulation as the luteal phase is induced
by exogenous progesterone administration. It has been put forward that the absence of the
corpus luteum, producing vasoactive and angiogenic substances (e.g. VEG-F, relaxin) and
thereby orchestrating a correct placental development, could be held responsible for this
observation. Other high risk ART patients are recipients of heterologous oocytes (i.e. oocyte
recipients) potentially due to immunological conflicts.
In 2016, the ASPRE trial published their results evaluating a new first trimester screening
tool developed by the fetal medicine foundation (FMF). This algorithm takes into account a
limited number of anamnestic maternal characteristics, maternal blood pressure, the
measurement of placental growth factor (PlGF) as a serum biomarker and the ultrasonographic
measurement of the pulsatility index of the uterine artery. When an increased risk of PE had
been detected (>1/100), aspirin daily is given, starting before 16 weeks' of gestation.
As of May 2021, the FMF first trimester screening for PE is offered in the Brussels IVF
fertility clinic to all the above-described high-risk patients pregnant following ART (PCOS
and oocyte recipients included). Preliminary data confirm a high incidence of positive
screening with an overall risk of 18%, reaching upto 27% in oocyte recipients (compared to
the reported 10% in the general population following spontaneous conception). To the best of
our knowledge, the applicability of the screening tool and aspirin administration for PE
prevention has never been specifically evaluated post-ART. PE etiopathogenesis is complex and
the exact molecular causative processes are still being unraveled. PE has a wide range of
clinical presentations and it is currently unknown what drives these differences. Of critical
importance for instance is the difference between early onset pre-eclampsia (EOPE), defined
as PE occurring before 34 weeks of gestation and late onset pre-eclampsia (LOPE), defined as
PE occurring at or after 34 weeks of gestation. In EOPE, which is mainly a placental disease,
the impaired invasion of the spiral arteries by the extravillous cytotrofoblast cells has
been put forward as the key pathophysiological component. This in contrary to LOPE, which is
seen as a maternal disease, where there is a discrepancy between fetal growth, aging of the
placenta an the maternal supply and cardiovascular reserve. Further, single-cell RNA
sequencing on placentas confirmed the extensive different expressed genes between EOPE and
LOPE. Also, the role of different serum markers (PlGF, sFLT-1, VEGF, leptin, annexin…) have
been studied, but their contribution to EOPE and LOPE still remains unclear.
Lastly, very limited but intriguing research data suggest that the preconceptional
endometrium could be implicated in PE development during pregnancy, with the focus on
impaired decidualization and its role in PE origin. Given the differences in patient
characteristics between the above-mentioned ART subgroups at risk for PE, our research team
expects their PE-etiopathogenesis to be diverse. Though the multidisciplinary approach of
this project, both on a clinical and fundamental research level, we hope to unravel
pre-eclampsia, a multifactorial disease, and this in specific relation to different ART
high-risk groups. This way, ultimately, the results will point towards targets for prevention
and treatment of PE following ART and will contribute to a decrease in the morbidity and
mortality associated with this devastating disease, for which, currently, no cure but
termination of the pregnancy is available.
Hypothesis:
Work package 1a: there is a significant difference in preconceptional maternal
characteristics between ART patients screening positive/developing PE and ART patients
screening negative/not developing PE and these identified risk factors are specific for each
ART subgroup.
Work package 1b: preconceptionally harvested endometrial tissue/stromal cells/organoids
harbor significant differences in function of the subsequent (i.e. during pregnancy) negative
or positive PE screening, PE development and specific high-risk ART group.
Work package 2a: the incidence of a positive screening/PE development (EOPE vs. LOPE) differs
significantly among different ART groups.
Work package 2b: parameters during the pregnancy (blood pressure, biomarkers in the blood,
ultrasound, nutritional and cardiac parameters) are significantly different between ART
patients screening positive/developing PE and these identified parameters are specific for
each ART subgroup.
Work package 3: placental tissue, membranes, cord tissue and cord blood harbor significant
differences in expressed molecular pathways depending on negative or positive PE screening,
PE development or not and are specific for the high-risk ART group.
Experimental design:
Prospective interventional cohort study without the use of a product nor medical device.
Methodology:
The study population will be subdivided into two different patient groups. Patients will be
asked to participate to the study when they are planning to undergo ART and are (already
prior to the start of their treatment) suspected to be at higher risk for the development PE
after achieving pregnancy:
Group 1 will include oocyte recipients as the use of donor oocytes predisposes them to a
potential immunological conflict during pregnancy contributing to PE development
Group 2 will include PCOS patients as endocrine and metabolic abnormalities predispose
them to an abnormal trophoblast invasion contributing to PE development Work package 1a:
evaluation of maternal baseline characteristics, laboratory studies, ultrasound
examination, cardiac and nutritional work-up.
Work package 1b: harvesting and biobanking of preconceptional endometrium during the luteal
phase of a preparative non-conceptional test-ART cycle (MOCK cycle). Depending on the outcome
of the pregnancy, tissue can be thawed and used for basic research experiments (stromal cell
lines, organoids, decidualization experiments, implantation experiments).
Work package 2a: patients are screened between 11- and 14-weeks' gestation using the FMF PE
screening algorithm (routine care at our center). When patients are determined to be at
high-risk of PE development (>1/100), they are advised to take aspirin (160 mg daily) until
36 weeks' gestation.
Work package 2b: patients will be followed up at different time points during their pregnancy
(7, 12, 20, 28, 36 weeks' gestation) using urine sampling, blood analysis, blood pressure
measurement, cardiac and nutritional work-up and ultrasound evaluation.
Work package 3: collection of placental tissue, membranes, umbilical cord tissue and cord
blood at time of delivery for basic research analysis. Evaluation of different molecular
pathways and expressed genes between no PE, EOPE and LOPE and this in specific relation to
the different high-risk groups.