Implantation and Pregnancy

Implantation and Pregnancy

About six days after fertilization, the embryo—then called a blastocyst—begins to implant into the uterine lining. This process, known as implantation, marks the beginning of the interaction between the developing embryo and the maternal uterus. It relies on close communication between the blastocyst and the endometrium. Several teams within the RQR are studying the different stages of implantation and pregnancy.

For the embryo to implant, the uterine lining (the endometrium) must be ready to receive it. This preparation includes decidualization, a process triggered by hormones that transforms endometrial cells to support embryo attachment. Éric Asselin’s lab seeks to understand how cells survive or die at the time of implantation, particularly during decidualization.

One of the critical steps following implantation is the controlled invasion of maternal tissue by trophoblasts, cells of embryonic origin that will give rise to the placenta. William Pastor’s team investigates how certain genes are switched on or off to allow the formation of trophoblasts and to guide the early development of the placenta. Carlos Reyes-Moreno focuses on trophoblast dysfunctions that may lead to pregnancy complications. Trophoblasts not only anchor the embryo into the uterine lining, but also establish the vascular network needed for maternal-fetal exchanges. Daniel Dufort’s lab studies the communication between the embryo and the uterus throughout pregnancy.

Proper programming of the placenta and fetus is essential for healthy fetal development and for preventing gestational complications. It is now well established that preconception, prenatal, and early-life conditions have a lasting influence on the health of the child. Factors such as stress, poor nutrition, or exposure to toxic substances can disrupt embryo implantation and early placental development, leading to adverse fetal programming. These disruptions increase the risk of diseases later in life, such as diabetes, obesity, or neurodevelopmental disorders. Sophie Petropoulos’s team seeks to understand how ex vivo conditions, like those used in assisted reproduction, may alter early gene and molecular activity in the embryo’s first cells.

Any disruption in implantation or trophoblast development can compromise pregnancy progression. Early abnormalities can result in spontaneous miscarriages or molar pregnancies, which are marked by abnormal placental growth without a viable embryo. Rima Slim’s team is working to identify new genes involved in recurrent molar pregnancies and repeated miscarriages. Maritza Jaramillo’s team studies the mechanisms by which toxoplasma infection disrupts placental function and affects fetal development.

Among pregnancy complications, preeclampsia is a complex syndrome that endangers both maternal and fetal health. To improve care for women with preeclampsia, Julie L. Lavoie’s team is developing tools for early diagnosis of this condition.

Complementing this research landscape on implantation and pregnancy is the work of Cathy Vaillancourt’s team, which explores how environmental factors—such as stress, depression, medications, or contaminants—can affect placental function and harm fetal development. Her team focuses particularly on serotonin and melatonin, two hormones produced by the placenta that play a key role in fetal heart and brain development. They also study how these effects may differ based on fetal sex and are developing innovative models, such as placenta-on-a-chip systems, to better understand the long-term impacts of these exposures on maternal and child health.