I took tetracycline 500 mg 5 tablets and doxycycline 100mg 4tablets off and on until my 5th wk of pregnancy. would it cause birth defects.

Should not be problm: Tetracycline is avoided in later pregnancy and childhood due to its interference with bone mineralization.Recorded use in the first trimester has not been shown to create problems with the fetus.

YES : Tetracycline can cause fetal toxicity when given to pregnant women.Fetal bone and teeth accumulation. In general, reports of exposure have been limited to short durations of therapy in the first trimester. Tetracycline may discolor fetal teeth following maternal use during pregnancy; the specific teeth involved and the portion of the tooth affected depends on the timing and duration of exposure.