Reijo Pera has cited her experience of developing a rare kind of ovarian cancer, called a granulosa cell tumour, early in her career as a motivating factor for her decision to study embryonic development and fertility.
The cancer resulted in her own loss of fertility.

In men, her research team and collaborators have investigated mechanisms of male infertility.
In a study published in 2000, she found that some infertile men have mutations in the genes required for DNA repair, which in turn may lead to defects in meiotic cell division—also known as meiotic arrest—and inviable sperm.
Defects in DNA repair mechanisms may result in DNA with a series of harmful mutations, so infertility may be nature's way of preventing offspring who inherit such mutations.
This study, done in collaboration with Paul J. Turek, raises concerns around men who have this condition undergoing intracytoplasmic sperm injection, whereby a sperm is directly injected into an egg, because their children may inherit defective DNA-repair machinery, increasing the likelihood of infertility and the risk of cancer.

Her research group has also worked on developing alternative solutions for men experiencing infertility.
In 2014, she published a method of deriving immature sperm cells from skin cells with the hope of ultimately making those sperm cells viable.
Her team extracted skin cells from infertile men and manipulated them to become induced pluripotent stem cells, which can subsequently become virtually any cell in the body—including sperm.
The study did stir up some controversy, leading to discussions around misuse of such a technology, though work remains to be done to ultimately produce viable sperm cells from this procedure.

Reijo Pera has also worked to develop methods to improve the chances of pregnancy during in vitro fertilization by identifying and selecting the strongest and healthiest embryos for implantation.
To do so, she essentially devised a method to film the embryo using a microscope as it divides for the first time and then measure the differences between that process across embryos to score which are the most viable.
Specifically, they score embryos based on the time it takes to complete the first three cell divisions (i.e. from one cell to 8).
Her team was able to predict with 93% accuracy which embryos had the greatest chance of resulting in a successful pregnancy.
This work was named a Top 10 Biomedical Breakthrough by Time in 2010.

More broadly, Reijo Pera has also worked to understand how pluripotent embryonic stem cells are ultimately able to mature into their specialized adult forms.
She and her collaborators decided to focus their attention on identifying certain developmental milestones that occur in an embryo one week after fertilization, measuring gene expression in individual cells.
They identified genes that were derived from the human endogenous retrovirus K, which activate key genes during early development and confer the embryo with immunity against other viruses.
They later found that the human endogenous retrovirus-H produced key RNA molecules that could either activate or silence genes, acting as "switches" for gene expression.
Her team found that these switches could help maintain pluripotency.
Reijo Pera has cited her experience of developing a rare kind of ovarian cancer, called a granulosa cell tumour, early in her career as a motivating factor for her decision to study embryonic development and fertility. The cancer resulted in her own loss of fertility.
In men, her research team and collaborators have investigated mechanisms of male infertility. In a study published in 2000, she found that some infertile men have mutations in the genes required for DNA repair, which in turn may lead to defects in meiotic cell division—also known as meiotic arrest—and inviable sperm. Defects in DNA repair mechanisms may result in DNA with a series of harmful mutations, so infertility may be nature's way of preventing offspring who inherit such mutations. This study, done in collaboration with Paul J. Turek, raises concerns around men who have this condition undergoing intracytoplasmic sperm injection, whereby a sperm is directly injected into an egg, because their children may inherit defective DNA-repair machinery, increasing the likelihood of infertility and the risk of cancer.
Her research group has also worked on developing alternative solutions for men experiencing infertility. In 2014, she published a method of deriving immature sperm cells from skin cells with the hope of ultimately making those sperm cells viable. Her team extracted skin cells from infertile men and manipulated them to become induced pluripotent stem cells, which can subsequently become virtually any cell in the body—including sperm. The study did stir up some controversy, leading to discussions around misuse of such a technology, though work remains to be done to ultimately produce viable sperm cells from this procedure.
Reijo Pera has also worked to develop methods to improve the chances of pregnancy during in vitro fertilization by identifying and selecting the strongest and healthiest embryos for implantation. To do so, she essentially devised a method to film the embryo using a microscope as it divides for the first time and then measure the differences between that process across embryos to score which are the most viable. Specifically, they score embryos based on the time it takes to complete the first three cell divisions (i.e. from one cell to 8). Her team was able to predict with 93% accuracy which embryos had the greatest chance of resulting in a successful pregnancy. This work was named a Top 10 Biomedical Breakthrough by Time in 2010.
More broadly, Reijo Pera has also worked to understand how pluripotent embryonic stem cells are ultimately able to mature into their specialized adult forms. She and her collaborators decided to focus their attention on identifying certain developmental milestones that occur in an embryo one week after fertilization, measuring gene expression in individual cells. They identified genes that were derived from the human endogenous retrovirus K, which activate key genes during early development and confer the embryo with immunity against other viruses. They later found that the human endogenous retrovirus-H produced key RNA molecules that could either activate or silence genes, acting as "switches" for gene expression. Her team found that these switches could help maintain pluripotency.
Renee Reijo Pera