Category B. The US Food and Drug Administration has assigned all drugs available into a pregnancy category. Cephalosporins are apparently safe in pregnancy and are in Category B.
Below is a table with the Pregnancy Risk Categories and examples:


Pregnancy Risk Categories
Category Example Description
A
(Low Risk)		 very few
Thyroid Hormones;
Pyridoxine (Vitamin B6)		 Studies in pregnant women show no adverse effects on the fetus during the first trimester of pregnancy, and there is no evidence of adverse effects in later trimesters.
B Penicillin VPotassium
( Pen-Vee K®)		 Studies in animals show adverse effects on the fetus, but human studies show no adverse effects on the fetus; OR Studies in animals show no adverse effects on the fetus, but human studies have not been done.
C

Ascorbic acid
(Vitamin C)

Acetyl-salicylicacid
(Aspirin)
category D in 3rd trimester

 Animal studies have shown an adverse effect on the fetus but there are no adequate studies in humans; the benefits of the drug in pregnant women may be acceptable despite its potential risks; or There are no animal reproduction studies and no adequate studies in humans.
D Paclitaxel (Taxol®) There is evidence of human fetal risk, but the potential benefits from the use of the drug in pregnant women may be acceptable despite its potential risks.
X(High Risk)

Diethyl-stilbestrol
(DES®)

Finasteride
(Propecia®)

Isotretinoin
(Accutane®)

Thalidomide
(Thalomid®)

Studies in animals or humans demonstrate fetal abnormalities or adverse reaction reports indicate evidence of fetal risk. The risk of use in a pregnant woman clearly outweighs any possible benefit.
NR Acet-aminophen
(Tylenol®)		 Not rated.


*http://pharmacology.miningco.com/health/pharmacology/library/weekly/aa970430.htm