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Fetal/Placental Ratio for Appropriate for Gestational Age Infants

Description

The ratio of fetal weight to placental weight tends to increase with increasing gestational age.


 

fetal-to-placental ratio =

= (weight of fetus in grams) / (weight of placenta in grams)

 

week gestation

F/P ratio low

mean F/P ratio

F/P ratio high

23

3.96

4.44

4.92

24

3.61

3.7

3.79

25

3.88

4.01

4.14

26

3.43

3.91

4.39

27

4.53

4.94

5.35

28

4.59

5.34

6.09

29

4.38

4.91

5.44

30

4.98

5.65

6.32

31

4.55

5.11

5.67

32

4.85

5.41

5.97

33

5.88

6.39

6.90

34

6.18

6.53

6.88

35

6.15

6.54

6.93

36

6.59

6.89

7.19

37

6.59

6.93

7.27

38

7.22

7.37

7.52

39

7.41

7.52

7.63

40

7.59

7.68

7.77

41

7.34

7.53

7.72

42

7.13

7.36

7.59

43

7.77

7.9

8.03

 

Initial line approximations:

 

F/P ratio low =

= (0.0004863 * ((week gestation) ^2)) + (0.1952285 * (week gestation)) -1.342432

 

F/P ratio high =

= ( - 0.0057 * ((week gestation)^2)) + 0.57497 * (week gestation) - 6.175338

 

Subsequent line approximation for the mean ratio:

 

mean ratio for gestational age =

= (-0.002618 * ((week)^2)) + (0.3851 * (week)) - 3.759

 


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