What stage during pregnancy is the most sensitive to damage by viruses?

The most sensitive stage during pregnancy to damage by viruses is the embryonic period.

This period begins with implantation of the fertilized egg in the uterine wall and continues to approximately week eight of pregnancy. During this time, the embryo's organs are forming, and it is most susceptible to damage by teratogens, such as viruses.

Viruses can cross the placenta and infect the embryo, causing a variety of birth defects. Some of the most common viral infections that can cause birth defects include rubella, cytomegalovirus (CMV), and herpes simplex virus (HSV).

Rubella is a particularly serious infection because it can cause a condition known as congenital rubella syndrome (CRS). CRS can cause a variety of birth defects, including heart problems, eye problems, hearing loss, and intellectual disabilities.

CMV is another common virus that can cause birth defects. CMV infection can cause a variety of problems, including hearing loss, vision problems, and developmental delays.

HSV is a type of herpes virus that can cause genital herpes. HSV infection during pregnancy can cause premature birth, low birth weight, and other problems.

There is no cure for viral infections during pregnancy, but some of them can be prevented with vaccines. Rubella vaccine is recommended for all women of childbearing age. CMV vaccine is not currently available, but research is underway to develop one. HSV vaccine is not recommended for pregnant women, but it can be given to women who are planning to become pregnant.