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Although described as "morning sickness," pregnant women can experience this nausea any time of day or night. The exact cause of morning sickness remains unknown. Nausea and vomiting in pregnancy is typically mild and self-limited, resolving on its own by the 14th week of pregnancy. Other causes should also be ruled out when considering treatment.
Quickening indicates the start of fetal movements, usually felt 14–26 weeks after conception, or between the fourth and sixth month. [5] [6] A woman pregnant for the first time (i.e., a primigravida woman) typically feels fetal movements at about 20–21 weeks, whereas a woman who has given birth at least once will typically feel movements ...
About 80% of miscarriages occur in the first 12 weeks of pregnancy. The underlying cause in about half of cases involves chromosomal abnormalities. [158] Stillbirth is defined as fetal death after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life.
According to a study conducted by Whitcome, et al., lumbar lordosis can increase from an angle of 32 degrees at 0% fetal mass (i.e. non-pregnant women or very early in pregnancy) to 50 degrees at 100% fetal mass (very late in pregnancy). Postpartum, the angle of the lordosis declines and can reach the angle prior to pregnancy.
Gestational age: 20 weeks old. Embryonic age: 18 weeks old. The fetus reaches a length of 20 cm (8 in). Lanugo covers the entire body. Eyebrows and eyelashes appear. Nails appear on fingers and toes. The fetus is more active with increased muscle development. "Quickening" usually occurs (the mother and others can feel the fetus moving).
Stages in prenatal development, with weeks and months numbered from last menstruation. In humans, the usual definition of preterm birth is birth before a gestational age of 37 complete weeks. [94] In the normal human fetus, several organ systems mature between 34 and 37 weeks, and the fetus reaches adequate maturity by the end of this period.