whenever we have even just one person at work who has chicken pox, they send ll of the pregnant ladies home - its very unlikely that anything can go wrong if you have already had th virus, but if you havent it can have very bad effects on the unborn baby.....

from another website, not sure if i should note which one, but its babycentre - mods please delete if i shouldnt not, but here you go:

I'm pregnant. Should I avoid contact with people with chicken pox?


If you had chicken pox as a child, you probably have no reason to worry. Your body has developed antibodies to the virus, making you immune to further infection. However, if you think that you've never had chicken pox, you should avoid contact with people with chicken pox or shingles, a related condition that can be passed on as chicken pox.
What are the risks if I do catch chicken pox?


Chicken pox can be more severe if you catch it while pregnant. Your doctor may offer you aciclovir, which reduces the severity and duration of chickenpox but only if it is given within 24 hours of you developing a rash. Aciclovir is believed to be safe during pregnancy but if you are less than 20 weeks pregnant doctors probably won't recommend it because of the theoretical risk of the drug affecting the baby.

The risks to your baby change greatly depending on when in your pregnancy you catch chicken pox. Before 13 weeks, the risk is small, with only 0.4 per cent of babies suffering any side effects. Babies whose mothers catch chicken pox between 13 and 20 weeks are at slightly greater risk. Around 2 per cent will be underweight when they're born or have birth defects such as scars, and eye problems. They may also be slow to reach the developmental milestones that your health visitor will be checking for.

If you catch chicken pox between 20 and 36 weeks of pregnancy your baby is unlikely to be affected, though he may develop shingles in his first few years of life. After 36 weeks, the risks increase again. If you contract chicken pox just before or after giving birth, the baby is at very serious risk. Should this happen to you, your baby will be given an injection of varicella-zoster immune globulin (VZIG), a blood product that contains chicken pox antibodies, to reduce his risk of being seriously affected by the disease.