HESI PN MATERNITY PROCTORED EXAM
VERSION 6
ANTEPARTUM
Stages of Pregnancy The third through eighth weeks after conception are called the embryonic stage. The fetal period starts 9 weeks after conception and lasts through the end of gestation.
Fetal Development: Embryonic Stage
Week 1 Free-floating blastocyst Weeks 2 to 3 The embryo is 1.5 to 2 mm long. Lung buds appear. Blood circulation begins. The heart is tubular. The neural plate becomes the brain and spinal cord. Week 5 The embryo is 0.4 to 0.5 cm long.
The embryo weighs 0.4 g. Double heart chambers are visible. The heart beats. Limb buds begin to form. Week 8 The embryo is 3 cm long. The embryo weighs 2 g. The eyelids begin to fuse. The circulatory system through the umbilical cord is well established. 1 / 4
Every organ system is present. Week 12 Fetus is 6 to 9 cm long. Fetus weighs 19 g. Face is well formed. Limbs are long and slender. Kidneys begin to form urine. Spontaneous movements occur. Heartbeat is detectable with a Doppler transducer between 10 and 12 weeks. Sex is visually recognizable. Week 16 Fetus is 11.5 to 13.5 cm long. Fetus weighs 100 g. Active movements are present. Skin is transparent. Lanugo hair begins to develop. Skeletal ossification takes place.
Week 20 Fetus is 16 to 18.5 cm long. Fetus weighs 300 g. Lanugo covers the entire body. Fetus has fingernails and toenails. Muscles are developed. Enamel and dentin are being deposited. Heartbeat is detectable with a regular (nonelectronic) fetoscope. Week 24 Fetus is 23 cm long. Fetus weighs 600 g. Hair on head is well formed. Skin is reddish and wrinkled. Reflex hand grasp is functioning. Vernix caseosa covers the entire body. Fetus can hear.
Week 28 Fetus is 27 cm long. Fetus weighs 1100 g. Limbs are well flexed. Brain is developing rapidly. Eyelids open and close. Lungs are developed sufficiently to provide gas exchange (lecithin forming). If born at this time, neonate can breathe. Week 32 Fetus is 31 cm long. Fetus weighs 1800 to 2100 g. Bones are fully developed. Subcutaneous fat has accumulated. Lecithin-to-sphingomyelin (L/S) ratio
is 2:1.
Week 36 2 / 4
Present because of the fetus’ nonfunctioning lungs, bypasses must close after birth to allow blood to flow through the lungs and the liver. Fetus is 35 cm long. Fetus weighs 2200 to 2900 g. Skin is pink and the body rounded. Skin is less wrinkled. Week 40 Fetus is 40 cm long. Fetus weighs 3200 g or more. 3Kg Skin is pinkish and smooth. Lanugo is disappearing.
L/S ratio is higher than 2:1.
Lanugo remains on the upper arms and shoulders. Vernix caseosa coverage decreases. Fingernails extend beyond fingertips. Sole (plantar) creases run down to the heels. Testes are in the scrotum. Labia majora are well developed. Fetal Circulation 3 / 4
Umbilical Cord Cord contains two arteries and one vein. Arteries carry deoxygenated blood and waste products from the fetus. Vein carries oxygenated blood and provides oxygen and nutrients to the fetus.
The ductus arteriosus connects the pulmonary artery to the aorta, bypassing the lungs. The ductus venosus connects the umbilical vein and the inferior vena cava, bypassing the liver. The foramen ovale is the opening between the right and the left atria of the heart, bypassing the lungs
Remember AVA: two arteries and one vein.
The arteries carry deoxygenated blood and waste products away from the fetus to the placenta, where these substances are transferred to the mother's circulation. The umbilical vein carries freshly oxygenated and nutrient-laden blood from the
placenta back to the fetus. Fetal HR: 160 to 170 beats/min in the first
trimester but slowing with fetal growth to Nagele's rule : Used to determine the estimated date o1f2d0etloive1r6y0/cboenafitnse/mmiennnt.ear or at term. Subtract 3 months from the first day of the last menstrual period (LMP), add 7 days, and then adjust the year as necessary.
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