There is another important scientific publication created by a panel of experts sponsored by the International Olympic Committee (IOC).
In the article, the experts tried to cover the scientific work done in the field of exercising during pregnancy in recreational and elite athletes.
These are the main points of their conclusion on strength training during pregnancy:
"Light-to-moderate weight training with free weights or weight machines generally has no adverse health effects during pregnancy."
actually, they even state that untrained women can benefit their health if they start a strength training program.
But as to elite athletes who train in harder intensity, like the ACSM, the panel also warn women from the Valsalva manoeuvr effect, which "may temporarily decrease blood flow to the fetus"
they also warn that "large increases in intra-abdominal pressure may harm the pelvic floor support, which may increase the risk of urinary or anal incontinence or pelvic organ prolapse during or after pregnancy."