The gestational sac is a fluid-filled space that contains the fetus, the amniotic cavity, and the extra-embryonic body cavity. From about 4-6 weeks of pregnancy, it is possible to see the pregnancy vesicle on ultrasound (it is better to look at vaginal ultrasound). During this time (from 5 and 1/2 weeks), the doctor should check whether the embryo is well implanted, whether there has been a hematoma and whether the heart is beating. Around the 6th week, a yolk sac forms inside the gestational sac, which secretes progesterone and nourishes the embryo (so it plays a similar role as the yolk in an egg) before the placenta appears.
See the movie: "How is your baby developing in the belly?"
1. The monthly cycle and fertility
As they mature, most women gradually become fertile. This means that our ovaries begin to produce eggs that can be fertilized. The first cycles of a maturing girl can be irregular and sometimes anovulatory. Ovulation is induced and stimulated by the so-called the hypothalamic-pituitary-ovary axis. The hypothalamus secretes the hormone GnRH, which stimulates the pituitary gland to produce FSH and LH. The task of FSH (follicle stimulating hormone) is, inter alia, stimulating the maturation of ovarian follicles (Graff's follicles). Once the follicle is large enough, its cells begin to produce oestrogens (female sex hormones also stimulated by FSH) which help to increase the growth of the mucosa and glands in the uterus.
The second important hormone involved in the menstrual cycle is luteinizing hormone (LH), which stimulates the egg to reach full maturity and causes the Graaf follicle to burst, releasing the egg. This is what we call ovulation or ovulation. Ready for fertilization, the egg leaves the ovary and enters the fallopian tube. At the same time, the hormones continue to work intensively on the lining of the uterus, causing it to grow. This is in case the egg is fertilized.
When an egg ready for fertilization enters the fallopian tube, the remainder of the Graaf's follicle transforms into a corpus luteum. If you want to capture the moment of ovulation, you can use, for example, ovulation tests, the thermal-symptomatic method, etc.
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During pregnancy, the levels of the chorionic gonadotropin, i.e. the hormone hCG, rise. Testing its concentration ...see the gallery
Women who are very desirous of having a baby often see their doctor on days 3 or 4 after their period is due.Often times, such a visit may disappoint them, because it is too early for the doctor to say something unequivocally. Similarly, the issue of performing an ultrasound examination at such an early stage is debatable. A woman should first take a home pregnancy test or a more reliable laboratory test to check the level of chorionic gonadotropin, the so-called the pregnancy hormone beta-hCG in the blood serum.
2. Ultrasound examination and the development of early pregnancy
Ultrasound examination is a useful diagnostic method in many clinical situations in women in the first trimester of pregnancy. This test is most often performed between the 5th and 10th week of pregnancy. At this time, the pregnancy can be visualized on the image and its location can be confirmed. Often times, it is also possible to indicate the gestational age and confirm the fetal heart rate.
Ultrasound examination at the stage of early pregnancy is performed in order to: assess the correctness of pregnancy development, determine the number of embryos, assess the condition of the chorion and amnion, and confirm the presence of a gestational sac. If a gestational vesicle can be visualized, its location should be documented, and the presence of a yolk sac and embryo should be assessed. In the first trimester of pregnancy, ultrasound can also diagnose pathological conditions, such as ectopic pregnancy or molar.
At the end of the 5th week of pregnancy, the diameter of the gestational sac is approximately 4.5 mm. Additionally, during this period, we find the presence of the yolk sac, while the embryo may still be invisible (thus excluding the presence of an acinar mole). The yolk sac produces progesterone, a hormone that plays an extremely important role in preparing a woman's body for pregnancy and, if fertilization occurs, in the early development of the embryo. By the 13th week, the parietal-seat size increases by an average of 1.1 mm per day. At the end of the 6th week of pregnancy, an embryo about 3 mm long is visible, and at the end of the 7th week, the amniotic cavity.
The visibility of the embryo on the ultrasound image and its size can be checked from about the 6th week. At this stage, the doctor examining the woman (using the ultrasound method) reads the correctness of the placement of the gestational sac. It also informs about the fetal heart function and any visible abnormalities that may threaten early pregnancy.
The fetal heart rate may be visualized at the end of the 5th week, but should always be visible at the end of the 9th week of pregnancy! At a later stage, during the ultrasound examination, the head and torso of the embryo can be visualized. For the proper assessment and measurement of the embryo length, the parameter CRL (parietal-seat dimension) is used.
From the 11th week of pregnancy, the basic features of limb development, the umbilical cord, and the first points of bone ossification become clearly visible in the image. Mainly due to the small size of the fetus, the identification and evaluation of congenital abnormalities at this stage of pregnancy consists only in identifying large abnormalities, e.g.
The visibility of the pregnancy bubble on an ultrasound image depends to a large extent on the individual woman's cycle. With 28-day menstrual cycles, a gestational vesicle can be visualized around day 32 from the first day of the last menstrual period. On the other hand, the level of beta-hCG ranges from 217 to 7138 mIU / ml (5 weeks).