There is a difference of opinion among experts regarding whether it is safe to drink even the smallest amount of alcohol during pregnancy. Some of your friends will ask you not to take the unnecessary risk of exposing your unborn child to alcohol, while others may tell you it is fine to indulge in an occasional glass of champagne. But in truth, drinking alcohol while pregnant can lead to a number of birth defects and other problems in a newborn baby, with the risks of complications depending on various factors including the stage of pregnancy as well as the amount of alcohol consumed and the frequency of drinking.
Many women continue drinking during the first few weeks (before noticing a missed period) of pregnancy without being aware that they are pregnant. Modern medical guidelines are recommending giving up drinking as soon as you plan having a baby or at least as soon as you find out you are pregnant. Alcohol is currently included in the FDA pregnancy category D  as there are evidences of its harmful effects on the fetus.
Alcohol leads to imbalances in female hormones that control reproduction, thus damaging fertility and reducing the chances of conceiving . But, that does not mean drinking can prevent pregnancy.
It is believed to be most harmful during the first trimester (the initial three months), the negative effects are not limited only to the initial weeks after conception. It can cause major damage to the baby later in pregnancy as well (when the brain and other important organs develop) .
Drinking during the first 12 weeks of pregnancy greatly increases the risks of birth defects as this is the time the major organs and systems begin to form . The neural tube (later forms the brain and spinal cord), heart, digestive system, circulatory system, sensory organs and skeletal system all start developing  shortly after the implantation of the zygote.
Alcohol is a toxic substance for your baby, which quickly enters your bloodstream and passes through the placenta to reach the fetus . It is not possible for the fetus’s under-developed liver to break down alcohol as fast as you can. As a result, the fetus has higher blood alcohol levels than you which cause serious cell damage .
Adding a bit of wine or vodka to certain recipes does not generally cause any harm to you or your baby as most of the alcohol gets burnt off in the cooking process.
Fetal alcohol spectrum disorders (FASD) are a group of birth defects that occur as a result of alcohol consumption by the mother during pregnancy. It is classified into :
These congenital conditions are characterized by various physical and mental defects in the baby with the principal symptoms including:
Other more serious complications of alcohol abuse during pregnancy may include:
Researchers cannot establish any safe amount to drink while pregnant until they find out the potential effects of specific amounts of alcohol at certain stages in pregnancy . But, drinking alcohol during the first trimester should be avoided due to the high risk of birth defects.
According to older government guidelines, a couple of standard drinks in a week during the second and third trimesters should not be harmful . However, currently the American Congress of Obstetricians and Gynecologists (ACOG) suggests pregnant women to refrain from alcohol until the baby is born to eliminate any risk of complication .
According to several recent studies, an occasional glass of red wine does not cause any harm to the fetus . Some even claim that children born to mothers who drank a few glasses of wine during their pregnancy are better behaved than those born to mothers who abstained completely . However, there is still much debate over the topic of drinking wine in pregnancy as many believe having one glass may make one want another, which may hurt the baby. So despite all the researches and studies, many doctors recommend avoiding any amount of wine just to stay safe.
Scientists have proved drinking over 6-7 units (1 unit = 10 ml pure alcohol ) in a week to increase the risks of FASD in the baby . Women in the habit of frequent binge drinking (consuming over 5 units on a single occasion) are more likely to have a baby with fetal alcohol syndrome (FAS) compared to those who drink the same amount over a longer time .
Home pregnancy tests (HPT) are based on the hCG (human chorionic gonadotrophin) hormone levels in your urine. Drinking alcohol cannot affect an HPT as it does not interfere with the production of functioning of this hormone .