Approximately 0.001% of the ejaculated sperm reach the vicinity of the egg. If 10 million sperm were ejaculated, only about 100 of them would reach the egg, and these would attack the egg at many points. It requires up to 100 sperm, acting at one point, to digest a path through the barriers external to an egg before one sperm can penetrate the egg itself and fertilize it. Thus, if only 100 sperm even reach the egg, the probability of fertilization would be essentially nil.
Embryology is the overall study of the prenatal development of a human or other organism. Teratology is only one aspect of embryology, dealing with abnormalities of development that result in prenatal death or deformities at birth.
Thalidomide produces its effect in the fourth to eighth week of development, when the limb buds are differentiating into fully formed limbs. This is why it produced infants with one or more limbs either absent or only partially formed.
To be triploid means to have three complete sets of chromosomes. Each cell would have 69 chromosomes (3 sets of 23 each). Triploidy results from nondisjunction during meiosis in the course of producing eggs or sperm, resulting in an abnormal egg or sperm with 46 chromosomes that unites with a normal gamete having 23 more.
If the woman were only four weeks into her pregnancy, then at the time of her heavy drinking the preembryo would not yet be attached to her uterine wall and drawing nutrients (or alcohol) from her bloodstream. She has relatively little cause for concern over her lapse, as compared to the concern about drinking during the time that an embryo or fetus is nourished via the placenta.
