Pregnancy (Determining Due Date)

Determining the gestational age is an important step in obstetrics and gynecology, as it allows you to determine the date of the upcoming birth and correctly assess the development of the fetus. There are several methods that allow you to determine the duration of pregnancy, including data on the time of the last menstrual period, the date of the first fetal movement and objective data from the examination of the pregnant woman.

The normal duration of pregnancy is 280 days, which is equal to 40 weeks or 10 obstetric months, starting from the first day of the last menstrual period. However, in some women, pregnancy may continue for less or longer than this period, leading to premature birth or post-term pregnancy, respectively.

There are several ways to determine the gestational age based on the size of the uterus. For example, at 6 weeks the uterus is slightly enlarged, has a spherical shape, and signs of Snegirev, Reiter, and Horwitz-Geghar are observed. At 8 weeks, the uterus reaches the size of a woman’s fist, and its bottom is at the level of the pubic symphysis, Piskacek’s sign appears. At 12 weeks, the uterus is the size of a man's fist, and the fundus is one finger's diameter above the pubic symphysis. At 16 weeks, the fundus of the uterus is located midway between the pubic symphysis and the umbilicus. At 20 weeks, the abdomen noticeably enlarges, the fundus of the uterus is located two fingers across below the navel, fetal movements appear and its heart sounds are heard. At 24 weeks, the fundus of the uterus is at the level of the navel. At 28 weeks, the fundus of the uterus is two fingers across above the navel. At 32 weeks, the navel is flattened and the fundus of the uterus is defined between the navel and the xiphoid process. At 36 weeks, the fundus of the uterus reaches the xiphoid process and costal arches. At 40 weeks, the fundus of the uterus drops to the level at which it was at 32 weeks of pregnancy.

Determining the gestational age at 32 weeks is an important stage for practical obstetrics, since during this period pregnant women receive prenatal leave. To determine the duration of pregnancy, doctors use data on the last menstruation, the date of the first fetal movement (at 20 weeks for primiparous women and at 18 weeks for multiparous women), as well as the size of the uterus at the first appearance at the antenatal clinic (with early appearance, the diagnosis is established more accurately). In addition, the height of the uterus above the womb, the ratio of the presenting part of the fetus to the entrance to the pelvis, the length of the fetus or its fronto-occipital size, measured by a pelvis, as well as ultrasound fetometry data, such as the size of the coccygeal-parietal size, abdominal circumference, biparietal fetal head size and other parameters.

To more accurately determine the duration of pregnancy, various formulas and calendars have been proposed, based on the timing of the last menstruation and the date of expected birth. However, it must be remembered that each pregnancy is individual, and determining the gestational age should be based on an integrated approach, taking into account both objective examination data and the individual characteristics of each woman.

In conclusion, determining the gestational age is an important step in obstetrics and gynecology, since it allows you to establish the date of the upcoming birth and correctly assess the development of the fetus. Various methods are used for this, including information about the last menstrual period, the date of first fetal movement and the size of the uterus during examination. Doctors can also use formulas and calendars to more accurately determine gestational age.