How do doctors determine how many months you have been pregnant?

Answer 1

I admit that i am not an Obstetrician but my basic medical training has equipped me fairly well enough to answer this one. Doctors employ a variety of methods to ascertain the gestational age of the fetus or the duration of pregnancy. (These terms are often used interchangeably although in some circumstances, they may convey slightly different meanings.) Traditionally, the duration of pregnancy is calculated from the date of the last menstrual period (LMP.) Once the diagnosis of pregnancy is established by whatever reliable means, the duration of pregnancy is calculated by simply counting the days from the first day of the last menstrual period. For a woman with regular menstrual cycles or one who keeps track with a calender, getting an accurate date may not pose a problem. For many others only an approximate value can be obtained by this method. A pitfall with this method is the fact that some pregnant women may actually bleed in the early months of an otherwise uneventful pregnancy and mistake this often ominous sign for her regular menses. Thus the calculations may be inaccurate by as much as two months. Clinicians also rely on their findings on physical examination. The uterus increases in size at a fairly predictable rate during pregnancy. The fundus, or the top of the uterus can be felt the level of the pelvic brim (bony ridge at the lower abdomen) at thirteen weeks (approximately three months) of pregnancy. The fundus then rises approximately one centimeter with each passing week. It reaches the umbilicus at roughly twenty eight weeks and the lower margin of the rib cage at thirty six. It then drops slightly over the next two weeks as the fetus descends into the pelvis. These methods may seen crude and unsophisticated but are surprisingly quite reliable regardless of the mothers physical stature and afford a quick and easy means of crosschecking calculated values with estimates from physical examination (provided you have a single fetus; with twins and triplets all calculations are off.) Ultrasound scans have long since revolutionized the monitoring of pregnancy. The ultrasound creates an image of internal parts as high frequency sound waves are reflected from tissue surfaces. The ultrasound scan can detect the gestational sac(or sacs), its location, size, the fetal heart beat (in viable pregnancies), the fetal size, location of the placenta etc etc. The ultrasound scan is considered fairly safe although its use is not without problems. Using the ultrasound scan, the clinician can record the dimensions of particular fetal structures at different stages of pregnancy eg. Crown rump length, biparietal diameter, femur length,etc (body length, head size, leg length respectively.) These values are compared with tables and graphs obtained from studies of fetuses in many pregnancies that were accurately dated to obtain the duration of the pregnancy in question. The values thus obtained are more accurate the earlier on in pregnancy they are obtained because of the smaller margin of associated error. As pregnancy progresses the estimated range widens. I hope this has been helpful. Thank You

Answer 2

see a doctor