Badly! There isn't a lot of evidence on the effect in humans (it's hard to talk anyone into experimenting on people, let alone pregnant women), but even a single dose of meth causes long-term neuro damage to experimental animals like mice. They fail to develop full learning and motor skills.

We know that using meth during pregnancy leads to higher rates of birth abnormalities, low birth weight, higher rates of hyperactivity, learning difficulties, diabetes and heart disease.

The most recent research suggests that the brain of the developing baby is much more sensitive to the effects of all amphetamines than previously thought, and that while many drugs taken by pregnant women have the greatest impact on the foetus during the third trimester, meth powerfully effects the babe right across the whole 9 months. Take care.