How much damage is done to a baby before a mother finds out she is pregnant?

Well the question does state that it leaves a month of being pregnant whilst drinking and smoking…

you would need to see a doctor and get testes done to see wether or not and if so, how much damae has been done. yes smoking and drinking can affect the baby in a negative way,though usually (but not always) only when continously done throughout the pregnancy…so when the person does that the whole time there pregnant. the sooner you quit (at least up untill after you give birth) the better it will be for the baby

If the pregnancy is determined within the first few weeks, the risks are minimal. An extremely high percentage of women have smoked and drank in their first month, not knowing they were pregnant, and went on to deliver healthy, normal babies.

There was a study done recently which investigated the effects of moderate amountd of alcohol in early pregnancy, which was carried out basically to bring some relief to worried women who had drank some amount of alcohol before finding out they were pregnancy, and they found it doesnt have a significant effect on the health of the baby. This was for moderate drinking though, heavy drinking would probably be different. The thing I would be most concerned with is actually if I had been getting enough folate before getting pregnant, as folate is most important very early on, often before you know you are pregnant, and not getting enough can result in the neural tube failing to close, leading to spina bifida or anencephaly. I try to eat a diet high in folate just in case!