P1: Alcohol is most harmful in the first trimester of pregnancy when most women will not look pregnant at all.
P2: A pregnant woman herself may not know she is pregnant for several weeks after the start of pregnancy.
P3: It is not feasible to rely on gossip about someone's eing pregnant, to administer on-the-spot pregnancy tests or to ban all women of childbearing age from buying alcohol.
P4: It is not fair to prevent pregnant women from purchasing alcohol for a function or a gift rather than their own consumption.
MP5: So, a law against selling alcohol to pregnant women would be ineffective, unenforceable, and unfair.
MP6: There should not be laws that are ineffective, unenforceable, and unfair.
P7: The vast majority of mothers do all they can to ensure a healthy baby.
MP8: So education of women about the harmful effects of alcohol during pregnancy is more likely to prevent pregnant women from drinking alcohol than a law against selling alcohol to pregnant women.
C: Therefore, instead of a law against selling alcohol to pregnant women, there should be education of women about the harmful effects of alcohol during pregnancy.
This is about as compact as it gets. Notice, that MP5 seems to depend on premises 1-4. There is a convention for diagramming the relationship between premises.