If you are an unmarried lady and have sex, you will get pregnant. No good will come of it.
If you are physically unable to get pregnant due to being male, the girl you had sex with will get pregnant. No good will come of it. You'll either kill her, or she'll kill herself, or her husband/brother/father/uncle/cousin will kill you both. In any case her Doleful Ghost will make sure everyone finds out. You will either get hanged, kill yourself, or be carried off bodily by Satan. Your last words will begin "Come all ye."
Going to sea to avoid marrying your sweetie is an option, but if she hangs herself after your departure (and it's even money that she's going to) her Doleful Ghost will arrive on board your ship and the last three stanzas of your life will purely suck.
If you are a young gentleman who had sex it is possible the girl won't get pregnant. In those rare instances you will either get Saint Cynthia's Fire or the Great Pox instead. No good will have come of it.
New York Girls, like Liverpool Judies, like the ladies of Limehouse, Yarmouth, Portsmouth, Gosport, and/or Baltimore, know how to show sailors a good time, if by "good time" you mean losing all your money, your clothes, and your dignity. Note: All of these places are near navigable waterways. In practical terms this means that if you're a sailor you're screwed (and so are any young ladies you happen to meet). See also: Great Pox; Doleful Ghost.
For a hearing of these educational tidbits, you can start with this recording of arrangements by Benjamin Britten. Just avoid the wee folk!