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Journal of the Anatomical Society of India

Determination of Gestational Age of Human Foetuses From Diaphyseal Lengths Of Long Bones - A Radiological Study

Author(s): Zeba Khan, Nafis Ahmad Faruqi

Vol. 55, No. 1 (2006-01 - 2006-07)

Zeba Khan, Nafis Ahmad Faruqi
AMU, Aligarh

Abstract:

The study was performed on 34 foetuses. Their limbs were stretched and fixed on the radiographic plates to avoid overlapping and shortening of image. Diaphyseal lengths femur, tibia, humerus, radius and ulna were measured with the help of divider and scale in A-P radiographs. Diaphyseal lengths were presented in tabular and graphic forms and analyzed for all the aforementioned bones separately. Radiological study showed maximum growth rates between 4th to 6th months in most of the long bones. The rate of growth for femur during aforementioned period was relatively higher i.e. >12mm per month. Growth rate of tibia was maximum (30.50mm per month) during 5th Month. Growth rate was high for humerus (>10 mm per month) during 4th month of intrauterine life. Growth rate for both radius and ulna were maximum during the 5th month (>13 mm per month). It was concluded that long bones grow with great variability of rate during the different periods of intrauterine life. Although femoral diaphyseal length seems to be relatively most important growth index for determination of gestational age. In terms of authenticity, different long bones may be considered for different gestational age groups.

Key Words: Gestational age, Foetal long bones, Organogenesis, Diaphyseal lengths.

Introduction

The process of development is ordinarily divided into two sets of sequential changes called embryogenesis and organogenesis. Although the embryogenesis has been extensively explored, the literature relating to the organogenesis appears relatively deprived of adequate scientific attention. Gestational age is the age of unborn baby. Proper assessment of foetal well-being requires an accurate knowledge of gestational age of the foetus (Machado et al., 2000). Radiological measurements e.g. lengths of foetal long bones, have been earlier considered to determine gestational age (Felts, 1954 and Mehta and Singh, 1972). Martin and Higginbottom (1971) reported on parallax radiological measurement of the femoral shaft in approximately 100 foetuses, the age ranging from 16 to 38 weeks. The method was mathematically complicated and the number of cases after 30 weeks was small but it showed that growth in length of the femur occurred at a regular rate for each week of gestation. Available evidence on the ontogeny of human limb bones reveal distinct patterns of pre and post natal growths. Early foetal development (2-4 months) is characterized by accelerated growth of the upper limbs (Langman, 1975; and Bagnall et al., 1982), while postnatal growth is characterized by accelerated growth of lower limbs (Watson and Lowery, 1967; and Meredith, 1978). Noback (1944) studied the ossification centres of the long bones in foetal specimens from 2 months to birth. He noted that ossification centres of the upper extremity form earlier than those of the lower extremity, and form in the sequence humerus-radius-ulna in the upper extremity and femur-tibia-fibula in the lower extremity. Interestingly embryological studies by Queenan et al., (1980); O’Brien et al., (1981); Hadlock et al., (1982); Jeanty et al., (1984) and Elejalde and de Elejalde (1986) have demonstrated strong correlations between the size of organs and gestational age as well as limb bones lengths and gestational age.

Unfortunately, none of these studies were considered in Indian foetuses. Direct measurement of the lengths of ossifying bones in human foetal limb bones has been the subject of several radiographic studies (Hodges, 1937; Brandfass and Howland, 1967; Owen et al., 1971 and Russell et al., 1972). However, most of these studies have been concerned with the assessment of foetal maturity and have concentrated on foetus in utero near term. The practical value of such measurements is debatable since they vary over a wide range due to differences in foetal position. These measurements in vivo have also led to disagreement on the actual rates of growth of the ossification centres in the long bones. In our study we have considered radiological method the results to find out the relative reliability and authenticity in morphometry as far as diaphyseal lengths versus gestational age is concerned. Most of the previous authors have considered femur only for this purpose. We have included maximum possible number of long bones in the body so as to expand the scope of our study. The aim of the present study therefore is as follows:

  1. To collect data of diaphyseal lengths of long bones in Indian subjects.
  2. To correlate diaphyseal lengths with gestational age
  3. To find out reliability and relative authenticity of different diaphyseal lengths in determination of foetal age.
  4. To determine the pattern of growth of different long bones.
  5. To correlate our findings with previous reports.

Materials and Methods

Thirty-four human foetuses were considered for radiological observations on foetal long bones. They were collected from Department of Obstetrics and Gynaecology, J.N. Medical College, and Shiva nursing home, Aligarh. Foetuses of all age groups without obvious congenital anomalies (e.g., anencephalus, spinabifida) were selected for the study. Immediately after delivery foetuses were put into jars having 10% formalin solution. Foetal foot lengths were used as parameter to assess the gestational age. Fair correlation between foot length and gestational ages was documented (Streeter’s, 1920). Foetuses were fixed on the radiographic plate. Limbs were stretched to avoid overlapping and shortening of the image. Three to four foetuses were exposed at a time on the radiographic plate. The foetuses were kept in a position to clearly visualize the upper and lower extremities. The anteroposterior radiographs of foetuses were taken (Fig- 1). Diaphyseal lengths were measured with the help of divider and scale. These measurements for each bone separately long bones were presented in tabular form as well as plotted against gestational ages to analyze the result.

Observation and Discussion

Radiological study showed maximum growth rates of femur between 4th to 6th months. Femur is the commonest long bone considered by the scientists to determine the gestational age of human foetuses (Felts, 1956 and Mehta and Singh, 1972). Lengths of femoral shafts measured by radiological method in our study were 63 mm at 8 months and 77 mm at 40 months. Martin and Higginbottom (1971) studies reported the length 62.5 mm at 8 months while 86.5 mm at 40 weeks. The former value is comparable but latter reading is quite high. Racial factor may be the reason as the Martin and Higginbottom’s sample was British. Femoral lengths on radiological observations were also reported by Warren (1999) in Americans who found the length as 35 mm at 5th month and 74 mm at 10th month. Fazekas and Kosa (1978) reported the lengths in Hungarian population and found it to be 33 mm at 5th month and 71 mm at 10th month. The values in the present sample is 29 mm at 5th month and 76 mm at 10th month, which seem to be comparable with both aforementioned reports. Martin and Higginbottom (1971) in their radiological study reported that the femur grows at rate of 12 mm per month in last 2 months of gestation. In our study the rate ranged approximately from 7mm to 9mm per month i.e. about 3-5mm lesser than previous reports. Maximum growth rate (Table I) of >12mm per month was noticed during early periods of gestational age i.e.4th,5th and 6th months of intrauterine life. Radiological observations on femur, while plotted, (diaphyseal lengths versus gestational age) indicate a linear growth curve (Fig-2).

Table I – Diaphyseal lengths of femur during intrauterine life

Femur Monthly measurement (mm)
Period Mean Growth rate
(per month)
Gestational age
(months)
3 4.50 -
4 16.83 12.33
5 29.33 12.50
6 42.00 12.67*
7 50.00 8.00
8 60.75 10.75
9 67.50 6.75
10 76.00 8.50
*Maximum growth rate

mean diaphyseal lengths of femur during intrauterine life

Fig 2: Graph showing mean diaphyseal lengths of femur during intrauterine life.

Radiological observations had shown that growth rate (Tibia II) of tibia was maximum (30.50 mm per month) during 5th month. Growth was quite fast (21.25) mm per month) even during the 7th month. Warren (1999) described the numerical value of tibial diaphyseal length about 29 mm during 5th month and 63 mm during 10th month. Fazekas and Kosa (1978) mentioned the said measurements exactly the same. Both the studies were based on radiological observations. Our parallel findings, on the other hand, showed the lengths as 46 mm and 69 mm during the 5th and 10th month respectively. Both the readings were on the higher side. The higher values in Indians compared to Americans and Hungarians were due to racial difference. Diaphyseal lengths plotted against gestational age showed a linear growth curves except in the later part of intrauterine life when the curve is almost horizontal due to minimal growth (Fig-3).

mean diaphyseal lengths of tibia during intrauterine life

Fig 3: Graph showing mean diaphyseal lengths of tibia during intrauterine life.

Humerus was next to femur widely used as parameter for determination of gestational age (Warren, 1999; Fazekas and Kosa, 1978; Queenan et al., 1980, Lai and Yeo, 1995). Humerus was also observed radiologically by previous scientists. Warren (1999) observed the humeral length in the foetuses of American population. He found the length at 5th month to be 27.85 mm and at 10th month to be 64.02 mm. Fazekas and Kosa (1978) found the said measurements in Hungarian population, to be 25.91mm and 61.91mm respectively. These values in Indian sample are slightly higher than the American and Hungarian population, a fact again due to racial difference. Rate of growth (Table III, Fig-4) on radiological observation were quite high (>12mm per month) from 4th to 6th months of intrauterine life. Parallel report does not exist in previous literature.

Table II – Diaphyseal lengths of tibia during intrauterine life

Tibia Monthly measurement (mm)
Period Mean Growth rate
(per month)
Gestational age
(months)
3 3.50 -
4 15.50 12.00
5 46.00 30.50*
6 37.50 -8.50
7 58.75 21.25
8 55.50 -3.25
9 64.00 8.50
10 68.50 4.50
* Maximum growth rate

Table III – Diaphyseal lengths of humerus during intrauterine life

Humerus Monthly measurement (mm)
Period Mean Growth rate
(per month)
Gestational age
(months)
3 5.50 -
4 15.83 10.33*
5 28.53 6.35
6 38.50 9.97
7 45.75 7.25
8 54.00 8.25
9 59.00 5.00
10 65.50 6.50
*Maximum growth rate

mean diaphyseal lengths of humerus during intrauterine life

Fig 4: Graph showing mean diaphyseal lengths of humerus during intrauterine life.

Radiological observations by Warren (1999) in American population indicated the length of radius as 23 mm at 5th month and 52.24 mm at 10th month. Parallel study by Fazekas and Kosa (1978) in Hungarian population projected the lengths of radius as 21.51 mm at 5th month and 49.84 mm at 10th month of intrauterine life. Our findings, 23.66 mm and 53.50 mm respectively were only slightly higher and therefore comparable to a large extent. Slight difference may be attributed to methodology and human error. Rate of growth (Table IV) was maximum during the 4th month (3.5 mm per week) and 5th month (13.41 mm per month). No related reports were found in previous literature. Growth in lengths of radius was linear i.e. steady as in previous long bones (Fig-5).

Table IV – Diaphyseal lengths of radius during intrauterine life

Radius Monthly measurement (mm)
Period Mean Growth rate
(per month)
Gestational age
(months)
3 5.50 -
4 15.83 10.33*
5 28.53 6.35
6 38.50 9.97
7 45.75 7.25
8 54.00 8.25
9 59.00 5.00
10 65.50 6.50
* Maximum growth rate

Radiological length of ulna (Table V) at 5th month is 27 mm and at 10th month is 64.50 mm in present study. Previous report by Warren (1999) mentions 26 mm and 59.37 mm respectively. Fazekas and Kosa (1978) mentions mean lengths of ulna diaphysis as 23.91 mm and 57.23 mm at 5th and 10th month respectively. Differences noticed were due to fact that our sample was Indian while Warren’s was American and Fazekas and Kosa’s sample is Hungarian. Rate of growth observed in radiological readings is maximum (13.17 mm per month) during 5th month of intrauterine life .No such reports exist in previous literature. For ulna also growth in lengths was linear (Fig-6). When growth rates of different long bones were compared, it was found that the gestational periods of maximum growths were different for individual bones. Therefore each bone seemed to carry its own importance and reliability in relation to gestational period.

mean diaphyseal lengths of radius during intrauterine life

Fig 5: Graph showing mean diaphyseal lengths of radius during intrauterine life

Table V – Diaphyseal lengths of ulna during intrauterine life

Ulna Monthly measurement (mm)
Period Mean Growth rate
(per month)
Gestational age
(months)
3 4.50 -
4 13.83 4.50
5 27.00 13.17*
6 35.50 8.50
7 41.00 5.50
8 50.25 9.25
9 58.50 8.25
10 64.50 6.00
* Maximum growth rate

mean diaphyseal lengths of ulna during intrauterine life

Fig 6: Graph showing mean diaphyseal lengths of ulna during intrauterine life

Conclusion

It was concluded that long bones grow with great variability of rate during the different periods of intrauterine life. Femoral diaphyseal length seemed to be relatively more important growth index for determination of gestational age. However if we consider the rate of growth >8mm per month as authentic index to determine the gestational age, then some long bones will be found more authentic during different periods as shown below:

Long Bone Period of Authenticity (months)
Femur 4,5,6,7,8,10
Tibia 5,7,9
Humerus 4,6,8
Radius 5,6
Ulna 5,6,8,9

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