what happen to the 5 months pregnant mother if she's suffering from STD and the effect to the baby?

Answer 1

I'll give you an actual link where you can find the EXACT same thing the person above copied and pasted, as well as some more information about pregnancy and STDs.
http://www.cdc.gov/std/STDFact-STDs&Pregnancy.htm

Take care!

Answer 2

STDs can have many of the same consequences for pregnant women as women who are not pregnant. STDs can cause cervical and other cancers, chronic hepatitis, pelvic inflammatory disease, infertility, and other complications. Many STDs in women are silent; that is, without signs or symptoms.

A pregnant woman with an STD may also have early onset of labor, premature rupture of the membranes surrounding the baby in the uterus, and uterine infection after delivery.

STDs can be passed from a pregnant woman to the baby before, during, or after the baby's birth. Some STDs (like syphilis) cross the placenta and infect the baby while it is in the uterus (womb). Other STDs (like gonorrhea, chlamydia, hepatitis B, and genital herpes) can be transmitted from the mother to the baby during delivery as the baby passes through the birth canal. HIV can cross the placenta during pregnancy, infect the baby during the birth process, and unlike most other STDs, can infect the baby through breastfeeding.

The harmful effects of STDs in babies may include stillbirth (a baby that is born dead), low birth weight (less than five pounds), conjunctivitis (eye infection), pneumonia, neonatal sepsis (infection in the baby's blood stream), neurologic damage (such as brain damage or lack of coordination in body movements), blindness, deafness, acute hepatitis, meningitis, chronic liver disease, and cirrhosis. Some of these problems can be prevented if the mother receives routine prenatal care, which includes screening tests for STDs starting early in pregnancy and repeated close to delivery, if necessary. Other problems can be treated if the infection is found at birth.
cdc.gov/std

In other words, discuss with your doctor. There are some treatments that do not affect the baby and some that may be necessary to do during the birth.