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Gestational age: 6 weeks and 0 days until 6 weeks and 6 days old. 43–49 days from last menstruation. Embryonic age: Week nr 5. 4 weeks old. 29–35 days from fertilization. The embryo measures 8 mm (0.31 in) in length and weighs about 1 gram. [4] Optic vesicles and optic cups form the start of the developing eye. Nasal pits form.
The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage.
[24] 70% of pregnancies with a single episode of reduced fetal movements are uncomplicated. [24] [25] In the UK, the Royal College of Obstetricians and Gynaecologists say that if you think your baby has stopped moving or is moving less and you are over 28 weeks pregnant you should contact your midwife.
Pregnancy usually occurs by sexual intercourse, but can also occur through assisted reproductive technology procedures. [6] A pregnancy may end in a live birth, a miscarriage, an induced abortion, or a stillbirth. Childbirth typically occurs around 40 weeks from the start of the last menstrual period (LMP), a span known as the gestational age.
The book consists of photographs charting the development of the human embryo and fetus from conception to birth; it is reportedly the best-selling illustrated book ever published. [1] Nilsson's photographs are accompanied by text, written by doctors, describing prenatal development and offering advice on antenatal care. [2]
In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization , and continues as fetal development . By the end of the tenth week of gestational age , the embryo has acquired its basic form and is referred to as a fetus .
According to data from 2003 to 2005, survival rates are 20–35% for babies born at 23 weeks of gestation (5 + 3 ⁄ 4 months); 50–70% at 24–25 weeks (6 – 6 + 1 ⁄ 4 months); and >90% at 26–27 weeks (6 + 1 ⁄ 2 – 6 + 3 ⁄ 4 months) and over. [22] It is rare for a baby weighing less than 500 g (1 lb 2 oz) to survive. [21]
Complete expulsion of the baby signals the successful completion of the second stage of labour. Some babies, especially preterm infants, are born covered with a waxy or cheese-like white substance called vernix. It is thought to have some protective roles during fetal development and for a few hours after birth.