Like HowStuffWorks on Facebook!

10 Must-have Tests During Pregnancy

Sexually Transmitted Diseases

In addition to checking the cellular composition of the blood during the early stages of a pregnancy, doctors will also screen blood samples for sexually transmitted diseases (STDs) such as HIV/AIDS, syphilis, herpes and hepatitis B and C. Additionally, a cervical swabbing will be used to check for gonorrhea and chlamydia.

Discovering these diseases early on in a pregnancy is vital, as they can all be passed on to the fetus. Syphilis and HIV can infect the baby while it is still in the womb, while other diseases like chlamydia, gonorrhea, hepatitis B and genital herpes can infect the baby during birth as it moves through the birth canal.

STDs can cause a range of complications for a baby including transmission of the disease itself, early delivery, eye infections (from gonorrhea and chlamydia), or much more severe consequences such as miscarriage or stillbirth (from syphilis).

In the case of HIV, medication can be given that reduces the risk of transmitting the disease to the baby from 25 percent to approximately 7 percent. Genital herpes, another viral infection, can't be cured, but doctors might recommend a C-section if a woman has an outbreak at the time of delivery. In the case of hepatitis B, if the virus was contracted early in the pregnancy, there is a less than 10 percent chance the disease will be transmitted to the baby. If it was contracted later in the pregnancy, the transmission rate increases to approximately 90 percent [source: ACOG].

Chlamydia, syphilis and gonorrhea can be cured with baby-safe antibiotics.