During pregnancy, unique vascular changes occur, associated with decidualization of the
maternal tissues in response to trophoblast invasion, first in the endometrium and
subsequently in the myometrial JZ. The JZ broadly represents the inner third of the
myometrium that, together with its overlying endometrium, is involved in placentation.
Defective deep placentation, defined by the absent or incomplete remodelling of the JZ
segment of the spiral arteries, may be associated with a spectrum of obstetrical
complications, ranging from late miscarriage and pre-term labour to fetal growth
restriction and pre-eclampsia.
Thus, the primary site of vascular pathology in pregnancies lies not in the placenta or
decidua but in the JZ. To understand how impaired remodelling of the myometrial JZ prior
to conception may predispose to subsequent defective deep placentation, it is important
to first describe the structural and functional changes in the JZ at the time of embryo
implantation, and subsequently analyse the distinguishing features of defective deep
placentation associated with different pregnancy disorders.
Thus, non-invasive assessment of the JZ prior to conception may turn out to be useful in
identifying those women at risk of major obstetrical complications.
This project aims to evaluate the relationship between the characteristics of the ZJ in
3D ultrasound, and major adverse obstetrical outcomes in assisted reproductive technology
(ART) treatments, namely in vitro fertilization cycles, intracytoplasmic sperm injection
and frozen embryo transfer (FET).
In a prospective and observational study with the inclusion of 200 cases, a 3D ultrasound
will be performed on the day on which the final oocyte maturation is triggered or, on
FET, on the day prior to the administration of progesterone.
After the quality of visualization of the JZ is classified, its thickness will be
measured and described as regular, irregular or interrupted.
The volume of the ZJ will be obtained by subtracting the endometrial volume from the
volume of the junctional zone and the endometrium.
These characteristics will be related to major obstetrical adverse outcomes:
pre-eclampsia, pre-term labour and fetal growth restriction. The relation with a
high-risk first trimester screening for pre-eclampsia will also be accessed.
After explaining the study and obtaining written consent, a 3D ultrasound will be
performed for uterine evaluation, on the day of the final oocyte maturation trigger in
cases of IVF / ICSI. In cases of FET, the ultrasound evaluation will be carried out on
the day before the start of the luteal phase support.
All ultrasounds will be performed in a standardized manner by the same operator. With an
empty bladder, in a lithotomy position, a 2D transvaginal ultrasound will be performed
using a GE Voluson 730 Expert® ultrasound, with an endovaginal probe with a 4-8MHz
frequency. Identification of endometriosis lesions or acquired uterine abnormalities such
as leiomyomas or adenomyosis will be exclusion criteria. After evaluating the number and
maximum dimension of the ovarian follicles and the endometrial thickness, the
three-dimensional volume box will be placed to encompass the entire uterus in
longitudinal section, with minimal inclusion of para-uterine structures. A maximum
acquisition angle of 90º and maximum quality will be used. To minimize artifacts, during
the acquisition both the probe and the woman must remain immobile, being asked to hold
their breath. Then, a three-dimensional volume will be generated by automatic 360º
rotation of the transducer. For each case, two volumes will always be obtained.