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Inherited Disorders and Birth Defects

STDs and Birth Defects



I am currently a 10th grader doing a research paper on the Surgeon General`s 10 leading health indicators. My topic is on responsible sexual behavior. I would like to know how do STDs affect the body and cause birth defects?


About 2-4% of babies are born with a birth defect (congenital malformation). Causes of birth defects such as chromosomal abnormalities and mutations in specific genes cause many of these, but about 10% of birth defects are due to teratogens. A teratogen is any drug, chemical, physical agent, maternal disease or infection that causes a structural (birth defect) or functional abnormality by affecting the embryo or fetus during pregnancy. The exact mechanism of how infections, including sexually transmitted infections, affect the developing embryo or fetus is not known in many cases. However, there are 4 major principles about why some agents (such as an STI) can be teratogenic. These include:

1) Timing - when during pregnancy did the exposure happen – was it during the time when organs are forming (early in pregnancy) or after the organs have formed

2) Dose – how much and /or for how long – usually the higher the dose or the longer the exposure, the more risk there is to be a problem

3) Genetic differences - the genetic make-up of the mother and the developing fetus plays a role in deciding if an agent will cause birth defects – not everyone who is exposed will have problems

4) The agent itself – not all chemicals or infections cause birth defects

Teratogens can cause malformations (birth defects), poor growth, problems with functioning or death (lead to miscarriage or stillbirth). Ways in which a teratogen can cause damage include: cell death, altered metabolism which leads to such things as the loss of precursors or substrates in cells, decreased energy sources for cell development or functioning, changing cell migration or cell interacting with one another and disruption of tissues.

Infections during pregnancy, including some sexually transmitted infections, can cause birth defects and other problems such as miscarriage, premature (early) delivery, and low birth weight. These include rubella (german measles), varicella (chicken pox), parvovirus B19 (Fifth disease), toxoplasmosis (a parasite found in cat feces), syphilis, cytomegalovirus (CMV which is a type of herpes virus), herpes simplex virus and HIV. If the mother has an infection during pregnancy, the virus or bacteria or parasite can be passed on to the developing fetus (via the placenta) so that the fetus becomes infected as well. Using the principles of teratology, the infection can lead to birth defects, poor growth, mental retardation, miscarriage or stillbirth.

The March of Dimes has a very good overview of birth defects, including infections during pregnancy and sexually transmitted infections (website below). Good luck with your project.

Related Resources:

March of Dimes

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University