Age determination of Fetus
Age of the Fetus
Haase’s rule-age in lunar months
- If Crown-heel length is
- If Crown-heel length is >25 cm, age in months = length / 5h
End of first month
- Length 1 cm, weight two and half gram
- Eyes are seen as two dark spots and mouth as a cleft
End of second month
- Length 4 cm, weight 10 gms
- Hands and feet are webbed
- Anus is seen as a dark spot
Age of the Fetus
End of third month
- Length 9 cm, Weight 30 gms
- Eyes are closed, pupillary membrane appears
- Nails appear and neck is formed
- Heart fully formed
End of fourth month
- Length 16 cm, weight 120 gms°
- Sex can be recognized
End of fifth month
- Length 25 cm, weight 400 gms
- Nails are distinct and soft°
- Light hairs appear on head°
End of sixth month
- Length 30 cm, weight 700 gms
- Eyebrow and eyelashes appear°
- Subcutaneous fat begins to be deposited°
- Testes are seen close to kidney
End of seventh month
- Length 35 cm, weight 900-1200 gms
- Nails are thick
- Eyelids open and pupillary membrane disappears
- Testes found at external inguinal ring
End of eighth month
- Length 40 cm, weight one and half to two kg
- Nails reach the tips of fingers
- Left testes in scrotum
End of ninth month
- Length 45 cm, weight two and half to three kg
- Scalp hair is dark and 4 cm long°
- Scrotum is wrinkled and contains both testes
End of tenth month
- Length 50-53 cm, weight 2.5-5 kg
- The nails project beyond the end of fingers but reach only the tip of the toes
Fusion of Skull sutures & Closure of fontanelle
|
Lateral and occipital fontanelles |
< 2 months |
|
Posterior fontanelles |
6 – 8 months |
|
Anterior fontanelle |
1.5 – 2 years |
|
Metopic suture |
3 years |
|
Basi-Occiput fusion with basi-sphenoid |
18 – 21 years |
|
Sagittal suture
|
30 – 40 years 40 – 50 years 50 – 60 years |
|
Coronal suture
|
40 – 50 years 50 – 60 years |
|
Lambdoid suture |
45 years |
Exam Important
Rule of Hasse
- Rule of Hasse is used to determine the age of fetus from crown to heel length in cm.
- During first five months, Length in cm = (Age in months)2
- After age of >5 months, Age in months = (Length in cm)/5
- The lack of cartilage and the easy foldability (lack of recoil are evident in the ear of premature infant at 26 weeks.
- Prominence of the labia minora in a premature female infant represents the gestational age of aprox 28 weeks.
- Heart is fully developed at 3 month age of intrauterine life
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