The best advice we can give is for your sister to avoid all forms of alcohol (beer, wine etc) during her entire pregnancy to be absolutely safe.
There is no safe time or "safe" amount of alcohol that she can consume during pregnancy because alcohol in the mother’s blood passes to the baby through the umbilical cord.
Besides causing fetal alcohol syndrome, alcohol during pregnancy can also lead to miscarriage, stillbirth, and a range of lifelong physical, behavioral, and intellectual disabilities.
