Very pregnant woman

Conceiving a child from a frozen embryo significantly increases the mother’s risk of developing a dangerous blood pressure disorder, new research suggests.

Conceiving a child from a frozen embryo can significantly increase the mother’s risk of developing high blood pressure, according to a study published in the journal. blood pressure.

  • Compared to pregnancies conceived naturally, pregnancies conceived through assisted reproductive technology using frozen embryos may have a 74% higher risk of developing hypertensive disorders.
  • In comparison, the risk of hypertension during pregnancy from fresh embryo transfer is the same as from a naturally conceived pregnancy.
  • High blood pressure during pregnancy can be a sign of preeclampsia, a serious pregnancy complication that is life-threatening for both the mother and the fetus.

According to new research published on September 26 blood pressureIn vitro fertilization (IVF) using frozen embryos can be associated with a 74% higher risk. Blood pressure problems during pregnancy. blood pressure It is the Journal of the American Heart Association. In comparison, the study found that pregnancies resulting from fresh embryos – the immediate transfer of a fertilized egg through in vitro fertilization (IVF) rather than from a frozen, fertilized egg – and pregnancies from natural conception were about the same risk of high blood pressure.

High blood pressure during pregnancy is often a symptom PreeclampsiaComplications of pregnancy, including persistent high blood pressure, which threaten the health and life of the mother and fetus. According to the American Heart Association. About 1 in 25 pregnancies in the United States result in preeclampsia.

Preeclampsia is a symptom of high blood pressure and kidney or liver damage in women after the 20th week of pregnancy. It occurs in 3% to 7% of pregnancies. In rare cases, preeclampsia can occur after the baby is born, usually within 48 hours. This is known as postpartum preeclampsia. Although the exact cause of preeclampsia is not known, the condition is thought to begin during pregnancy.

One IVF treatment process uses frozen embryos: After the egg is fertilized with sperm in the laboratory, it is thawed and frozen in a cryopreservation process before being transferred to the uterus. With the introduction of greatly improved freezing technology, or cryopreservation, in the late 2000s, and more patients opting to freeze embryos, the procedure is becoming more common, the study authors said. However, frozen embryo transfer is known to be associated with a higher risk of hypertensive disorders than natural conception and fresh embryo transfer. However, before this study, it was not known whether this was due to the cooling process or the parents’ concern.

“Frozen embryo transfer is now becoming more common around the world, and in the past few years some doctors have begun to skip fresh embryo transfer in order to routinely freeze all embryos in their clinical practice. Cindre H. Peterson, MD; The study’s lead author and Ph.D. Fellow at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway.

In vitro fertilization (IVF) is a process in which an egg is removed from a woman’s ovary and combined with a sperm from outside the body to create an embryo. After growing in the laboratory for several days, the embryos are either placed in the woman’s uterus or cryopreserved for future use.

Investigators examined national data from medical birth registries in Denmark, Norway, and Sweden on nearly 2.4 million women between 1988 and 2015 who gave birth to singletons and gave birth between 20 and 44 years of age between 1988 and 2015. These data were the starting point. A population-based study also includes a comparison of women who had both an IVF pregnancy and a naturally conceived pregnancy, called a sibling comparison. This approach has been used to determine whether the cause of hypertensive disorders is due to parental factors or IVF treatment.

The study included more than 4.5 million pregnancies, of which 4.4 million were conceived naturally; More than 78,000 pregnancies with new embryo transfers; And more than 18,000 pregnancies were arrested embryo transfers. More than 33,000 of all pregnancies were assigned to sibling comparisons—mothers with more than one of these methods. The study is the largest to date using sibling comparisons. The odds of hypertensive complications during pregnancy after fresh and frozen embryo transfer compared with natural conception were adjusted for variables such as year of birth and maternal age.

“In conclusion, though, most IVF pregnancies are healthy and uncomplicated,” Peterson said. “This analysis shows that hypertension during pregnancy is higher compared to frozen embryo transfer or natural conception pregnancies.”

Specifically, the study found the following:

  • In a population analysis, women whose pregnancies were the result of frozen embryo transfer were 74% more likely to develop hypertension during pregnancy compared to those who conceived naturally.
  • In women with natural conception and frozen embryo transfer IVF conception (sibling comparison), the risk of hypertension during pregnancy after frozen embryo transfer is twice as high as compared to naturally conceived pregnancies.
  • Pregnancies from new embryo transfer compared with natural conception did not have an increased risk of hypertensive disorders, either in population-level analyzes or in sibling comparisons.

“Our sibling comparison suggests that the increased risk is not due to factors related to the parents, but some IVF treatment factors may be involved,” said Petersen. “Future research should examine which aspects of the frozen embryo transfer process may increase the risk of hypertension during pregnancy.”

Among other findings, the women in the study who gave birth after IVF pregnancies averaged 34 years for frozen embryo transfer, 33 years for fresh embryo transfer and 29 years for natural conception. About 7% of babies conceived from frozen embryo transfer are born prematurely (before 40 weeks’ gestation), and 8% of babies born after fresh embryo transfer are born prematurely, compared to 5% of babies born naturally.

In addition to early preeclampsia, scientists have described hypertension in pregnancy as a combination effect; Pregnancy blood pressureEclampsia (seizure onset in early preeclampsia) and chronic hypertensive preeclampsia.

One limitation of the study was the lack of data on the type of frozen fetal cycle, so it could not distinguish whether frozen cycle or frozen transfers contributed to the risk of hypertensive disorders. Another limitation is that data from Scandinavian countries may limit the generalizability of the findings to populations in other countries.

“Our results show that careful consideration of all benefits and potential risks is needed before freezing all embryos as a routine in clinical practice. A comprehensive, personalized discussion between physicians and patients about the benefits and risks of fresh and frozen embryo transfer is key,” said Petersen.

Reference: “Hypertensive complications in pregnancy after fresh and frozen embryo transfer in assisted reproduction: a population-based cohort study with sibship analysis” by Sindre H. Petersen, Kjersti Westvik-Johari, Ann Leekke Spangmos, Anja Pinborg, Liv Bente Romndstad, Kristina Berg, Bjørn Olav Esvold, Mika Geisler, Ayla Tittin, Ulla-Brit Wennerholm, and Synge Opdahl, 26 September 2022; blood pressure.
DOI: 10.1161/HYPERTENSIONAHA.122.19689

Co-authors Kjersti Westvik-Johari, MD, Ph.D.; Ann Laerke Spangmos, MD, Ph.D. Anja Pinborg, MD, Ph.D. Liv Bente Romundstad, MD, Ph.D.; Christina Berg, M.D., Ph.D. Bjørn Olav Åsvold, MD, PhD. Mika Gissler, Ph.D. Aila Tiitinen, MD, Ph.D. Ulla-Britt Wennerholm, MD, Ph.D.; and Signe Opdahl, MD, Ph.D.

The study was funded by the Norwegian University of Science and Technology, the Nordic Council of Ministers and Nordforsk, the regional health authorities of Central Norway, the Nordic Federation of Obstetrics and Gynaecology, Interreg Øresund-Katt-Skagerrak, the European Regional Development Fund and Research. Norwegian Council of Centers of Excellence.

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