Search results
Results from the WOW.Com Content Network
It begins between the 4 and 8 weeks of pregnancy and usually subsides by 14 to 16 weeks. The exact cause of nausea is not fully understood but it correlates with the rise in the levels of human chorionic gonadotropin , progesterone , and the resulting relaxation of smooth muscle of the stomach.
By seven weeks of gestation, the anterior pituitary vascular system begins to develop. During the first 12 weeks of gestation, the anterior pituitary undergoes cellular differentiation. At 20 weeks of gestation, the hypophyseal portal system has developed. The Rathke's pouch grows towards the third ventricle and fuses with the diverticulum.
The first ten weeks of gestational age is the period of embryogenesis and together with the first three weeks of prenatal development make up the first trimester of pregnancy. From the 10th week of gestation (8th week of development), the developing embryo is called a fetus.
Histopathology of placenta with increased syncytial knotting of chorionic villi, with two knots pointed out. The following characteristics of placentas have been said to be associated with placental insufficiency, however all of them occur in normal healthy placentas and full term healthy births, so none of them can be used to accurately diagnose placental insufficiency: [citation needed]
The presence of hCG in a woman's body indicates that a fertilized egg has implanted in the uterus and the placenta has started to form. 10 days after fertilization, significant hCG can be detected from woman's blood sample. [6] The levels of hCG in the body increase rapidly in the first few weeks of pregnancy, doubling every 48–72 hours. [7]
hPL is present only during pregnancy, with maternal serum levels rising in relation to the growth of the fetus and placenta. Maximum levels are reached near term, typically to 5–7 mg/L. [3] Higher levels are noted in patients with multiple gestation. Little hPL enters the fetal circulation. Its biological half-life is 15 minutes.
Menstrual cycle. The menstrual cycle is on average 28 days in length. It begins with menses (day 1–7) during the follicular phase (day 1–14), followed by ovulation (day 14) and ending with the luteal phase (day 14–28).
The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation, and increases to ca 45 mmHg at 40 weeks of gestation. [16] The fetal pulse pressure is ca 20 mmHg at 20 weeks of gestation, increasing to ca 30 mmHg at 40 weeks of gestation. [16] The blood pressure decreases when passing through the placenta.