Determination of term of pregnancy is necessary for its correct conducting and definition of estimated date of childbirth. Term can be estimated in calendar months – normal pregnancy on average lasts nine months and seven days of the first day of the last periods. But obstetric months are more often used, each of which is equal to 28 days. In this case pregnancy lasts 10 months or 40 weeks. There are several ways of determination of term.
Instruction
1. Calendar method. We find date of the first day of the last periods in the calendar and we count the number of the weeks which passed from now on. The result is divisible on 4. For example, there passed 17 weeks and 3 days, the term of pregnancy 17-18 weeks or 4 months 1 weeks and 3 days means.
2. Determination of term by means of tables. There are special tables by which it is possible to determine pregnancy term, having combined today's date with date of the first day of the last periods. In fact it is a modified calendar method.
3. Ultrasonography. This method is the most exact on initial terms. Up to 12 weeks the term is defined with a margin error in 1-3 days. Then every month the error increases, in the second trimester up to 7 days, and in the third the mistake can reach 2 – 3 weeks. The fact is that in this case doctors are guided by the fruit size. At the beginning of pregnancy it depends on term, and by the time of childbirth the size and mass of the child depends on specific features.
4. Determination of term of pregnancy at gynecologic inspection. The experienced doctor at the beginning of pregnancy quite precisely determines its term by the uterus size. In 4 weeks (1 month) a uterus of the size of egg, in 8 weeks (2 months) about goose egg, in 12 weeks (3 months) about a male fist.
5. More late pregnancy is determined by height of standing of a bottom of a uterus. In 4 months (16 weeks) the bottom of a uterus is a boundary a bosom (pubic bones) and a navel in the middle. In 5 months (20 weeks) the bottom of a uterus is at distance of 11-12 cm over a bosom. In 6 months – at the level of a navel. In 7 months (28 weeks) is 4 cm higher than a navel. In 8 months – in the middle between a navel and a xiphoidal shoot of a breast. In 9 obstetric months (36 weeks) a uterus bottom at costal arches, at the level of a xiphoidal shoot. By the time of childbirth (40 weeks) the uterus falls by the middle between a navel and a xiphoidal shoot.
6. On uterus length. Measure by a centimetric tape distance between a bosom and a bottom of a uterus. The number of centimeters is equal to the number of weeks of term. Having divided result into 4, we will receive month of pregnancy.