Anthropometric measurement of the developing fetus
Anthropometry is defined as the scientific study of the human body measurements and proportions. These studies are generally used by clinicians and pathologists for adequate assessments of the growth and development of the fetus at any specific point of gestational maturity. Fetal height, fetal weight, head circumference, crown to rump length, dermatological observations like skin thickness etc. are measured individually to assess the growth and development of the organs and the fetus as a whole and can be a parameter for normal or abnormal development also including adaptation of the fetus to its newer environment.
Another important factor that contributes towards the anthropometric measurement of the human fetal growth is the maternal nutrition and maternal well-being. Malnutrition, as already established by WHO, is a global serious health problem not only in adults but in pregnant and lactating mothers too and is a serious problem in third world countries. In Africa and South Asia, 27%-50% of women in the reproductive age are underweight resulting in 30 million low birth weight babies.
For decades, the topic of question pertaining to crown-rump length, crown-heel length, head circumference with respect to the body weight of human fetus at different time periods of gestation has baffled many developmental researchers and biostatisticians. These biological variations are all based on linear curves based on human fetuses between 9 and 28 weeks of gestation.
Co-relation of fetal weight and fetal growth
Body weight, for example, is an important function and parameter for growth with respect to gestational age of the fetus. There will be great variations in the body weight of a 16 weeks old fetus. The weight will not be constant for every fetus and will vary from individual to individual. Therefore, rather than an appropriate or standard value, a range can be specified like 90 to 100 grams. This number of variations applies to all other anthropometric measurements. Often, the scientific world cover up their ignorance by stating that the rate of growth of particular human fetus depends on its intrinsic growth potential and environment provided by the normal mother. It is a visible function of the genetic potential.The fetal growth is not an individual growth and is dependent on the composite growth of the organs. Growth of the individual organs is controlled by the genetic potential, the environment provided by the mother and by the fetus itself. Scientists have or are trying to determine such relationships through series of investigations.
Streetr, Schults et al., all studied the fetal dimensions obtained from spontaneous abortions and pathological pregnancies on mainly formed and fixed specimens. The growth of an organ from inception to a definitive functional stage is dependent on the integrated function of the whole organism which depends on a number of parameters such as the nucleic acid content of the cells which is one of the most important factors. Functioning of an organ is important for development of the organism.
A Nigerian study showed that the birth weight of the human fetus also depends upon the size and weight of the mother including her height and weight. Further a Polish study reported a similar report that some measurements like the ear height, muscular strength of the shoulders, skin fold thickness, mandibular breadth including the height of the upper and the lower limbs can be co-related to the mother also. Similar observations were also reported by Gueri et al.
One of the first original and unique works to be conducted on the anthropometric measurement of the human fetus in the Indian context was conducted by a group of scientists in Calcutta between 1977 and 1987 under the supervision of K.L.Mukherjee, a stalwart in the field of medical biochemistry in Institute of Post Graduate Medical Education and Research. The researchers divided the fetuses into 6 groups consisting of A, B, C, D, E and F with a difference of 4 weeks of gestation period among the 6 groups. Group A had 90 fetuses of 9–12 weeks of gestation and the weight varied between 1-14 grams. Group B had 337 fetuses, age 13–16 weeks of gestation with weight variation between 15 and 105 grams whereas the third group had 435 fetuses of 17–20 weeks of gestation with a weight range between 106 and 310 grams. Group D consisted of 531 fetuses of 21–24 weeks and weight between 331 and 640 grams and Group E had fetuses of the age range 25–28 weeks of gestation and weight 640-1070 grams. The last two groups F and G had fetuses with gestation period between 29-32 and 33–36 weeks. All aborted fetuses were collected after permission from the institute ethics committee followed with donor consent form with primary objective being the aborted mother's health and safety.
Liver growth
Researchers observed that the liver weight is directly proportional to the body weight. At 8–12 weeks of gestation, liver is a relatively bigger organ which forms 4-5-5.5% of the total body weight and protrudes through the abdominal wall. By 13 to 32 weeks of gestation, it forms 3.4% to 4.0% of the total body weight. The liver weight hence forms a more or less constant proportion of the total body weight of the fetus.Growth of the lung
Although in adult life, the lung is the only major respiratory organ, in case of fetal life such is not the case though the fetal lung is known to expand and contract in the last phase of development. Both the weight of the right and left lungs are normally assessed at different periods of gestation and is expressed as a function of the total body weight.An irregular graph was observed by K.L.Mukherjee and his group instead of the standard normal linear graphs which should be normally observed after plotting a graph of weight of the lungs expressed as gm/kg of body weight against the body weight. This relationship was observed from fetuses weighing 350 grams to 850 grams after which the rate of the growth became uniformly proportional again.