Thanks for your query at DoctorSpring.
Please consult your Obstetrician immediately if your wife had bleeding.
There could be some possibilities here.
First is that your wife has a placenta that is situated in the lower part of the uterine cavity ( normally it is implanted in the upper part ).
In this case, the bleeding could endanger the life of the baby. This is called placenta previa.
A second possibility is that the intercourse and the jerks could dislodge the placenta causing it to separate from the uterine wall ( placental abruption ) which is also dangerous for the mother and the baby.
Intercourse could sometimes trigger off mild uterine contractions, and hence cause bleeding from the cervical canal , this is not very dangerous.
However, you should definitely have an opinion from your doctor to rule out any potential risks.
An ultrasound scan would further confirm the safety of the baby .
Take care, and please feel free to discuss further.