Lovenox is usually given on a weight-adjusted basis for people with mechanical valves. In the African study the dose was not adjusted as the pregnant women gained weight. 20% of them and their fetuses died. From this the FDA jumped to the conclusion that nobody with valves should use Lovenox. This has since been reversed. However, Lovenox has not been studied very well in pregnant women. So there is no official FDA approval for its use in pregnancy. This does not necessarily mean that it is harmful, just that there is not enough data to draw any conclusion as to its safety or harmfulness.
One thing that is known is that people who have to use Lovenox (and probably Fragmin or Innohep etc) long-term do lose some calcium from their bones. A developing baby draws a lot of calcium from its mother's bones. Whether or not this can adequately be replaced by taking calcium is not known. Neither is it known whether or not this will cause a woman to have osteoporosis later in life. These products have only been on the market for about ten years so there are no long-term databases to make valid conclusions.
