Since there is a decently high risk of miscarriage in the first trimester, a lot of expecting parents keep the news to themselves. The general theory seems to be that they don’t want to have to bring the bad news by later once everyone has gotten all excited. The tradeoff here is that a lot of people are going to be wondering where you have disappeared to, why you aren’t reliable about showing up to dinners and parties and so forth, what all the bathroom breaks are for, etc. In the unhappy event that you do miscarry, they will further not know why you are now morose. When you tell who will depend on your relationships with the people around you, and how much of an impact this pregnancy is having on you. If you’ve got hyperemesis (the technical term for can’t even keep water down), you likely will have to let people know quite early. If your job exposes you to scary stuff that you don’t want near your developing baby, you will also need to speak up sooner.
Gestational Age aka How Many Weeks Along Am I is calculated in the following way: how many weeks has it been since your last period? That is how far along you are in your pregnancy. The textbooks say that women ovulate 14 days, or two weeks, after the first day of their period. In the unlikely event that you match the textbooks, you are two weeks pregnant on the date of conception. You are four weeks pregnant at the earliest time you could use a home pregnancy test to determine you are, indeed, pregnant, at which point the embryo is two weeks old. Your due date will be calculated on a little wheel that shows forty weeks as full-term (Naegele's rule), despite the fact that a completely normal pregnancy might last 38-42 weeks from the first day of the last period, and despite the fact that the averages are different depending on your race, age, parity (whether this is your first or a later child), gender of the child and whether you are a smoker.
For non-black women, for your first child, 288 days is a better guess than the 280 that is standard (so expect to be one week and one day past your due date). For later children, 283 days is a better guess. Or use Mittendorf's rule.
Why the weirdness? Many women do not have a regular cycle. Those who do have regular cycles have cycles longer or shorter than 28 days more often than exactly 28 days. Most women do not ovulate exactly 14 days after the first day of their period. (And, despite what some people say, they may not ovulate 14 days before their next menstrual period, either.) Further, some women ovulate more than once between bleeding. In a reasonable world, a woman who says she knows when she ovulates would be able to get health care practitioners to use the date of conception she supplies. But we don’t live in a reasonable world. If you know when you ovulate and you haven’t already established that your health care practitioner will believe you when you say you know when you ovulated, you can tell your health care practitioner that your last menstrual period (LMP) was fourteen days before when you know you ovulated, and do not deviate from that claim. This will save you all the hassle of showing them a bunch of thermometer readings and so forth. I mention this because I’ve run across a few too many women now who told the truth about their period, were unable to convince their doctor they ovulate three weeks into their cycle, and were induced early because doc thought they were late, and had a slightly undercooked baby as a result. This entire system smells of paternalism and calls for subversion, imo, but let your relationship with your health care practitioner be your guide.
The LMP dating system is particularly stupid when used on women who continue to have periodic bleeding early in their pregnancies or even throughout their pregnancy.
Copyright 2005 by Rebecca Allen
Created May 20, 2005 Updated May 23, 2005