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Determination of placental size using two dimensional sonography and its relation with gestational age

B. M. Patil^1*, Pradeep Kulkarni², U.T. Bhosale³, Kuljit Kaur⁴

{¹Lecturer, ³HOD, ⁴Junior Resident, Department of Obstetrics and Gynaecology}, {²Professor, Department of Radiology} Bharati Vidyapeeth Medical College and Hospital, Sangli, Maharashtra, INDIA.

Abstract               Introduction: An abnormal placental size has been linked to increased perinatal complications, including IUD and IUGR. Location, size, shape and architecture of placenta are easily ascertained with 2 dimensional technologies. Here we are making an effort to directly relate the size/area of placenta with gestational age which may ultimately give some idea about perinatal complications. The method is simple, rapid making it practical for routine for ante natal care and high risk cases.

Keywords: placental size/area, USG, IUGR, IUD.

 

INTRODUCTION

Placenta is an important organ of pregnancy and is solely responsible for intra uterine welfare of fetus. It is short lived highly vascularized organ that is indispensable for the growth and maturation of the developing fetus. With usg, the placenta can be easily visualized and presumably completely safe throughout pregnancy¹. USG is now the standard technique in diagnosing IUGR. Abdominal circumference is the single most sensitive parameter to detect iugr². The present study was conducted to assess the relationship of placental size with gestational age on two dimensional USG.

Aim: to study variation in placental size with gestational age on ultra sonography.

MATERIAL AND METHODS

The present study was carried out randomly on 100 pregnant women in 2^nd and 3^rd trimester (13 weeks to 40 weeks) in the department of radiology and department of obstetrics and gynaecology.

 

Methodology

Informed consent of pregnant women along with detailed history was taken and the information was kept confidential.

Women with singleton pregnancy without uterine and placental anomalies were in included in the study. Women having fetus with abnormalities of skull and/or abnormal femur length (skeletal dysplasia) were excluded from the study.

 

Scanning Technique

All ultrasound examinations were performed with sonosite m turbo machine equipped with 3.5 MHz transducer. The antenatal scan was done by single observer to eliminate interobserver variations. All the scans were done by using Tran’s abdominal approach. The patients were scanned with a full bladder in a supine position. The abdominal wall was liberally smeared with coupling gel to secure absence of air gap between the skin surface and transducer.

Fetal Measurement

The measurement of fetalbiparietal diameter (BPD) and femur length (FL) were obtained from 13 weeks of gestation whereas abdominal circumference (AC) was measured from 18 weeks of gestation. Femur length (FL) was obtained by measuring its ossified shaft (diaphysis). An acoustic shadow of femur was casted and the FL was measured. Abdominal circumference (AC) was measured in transverse plane perpendicular to the fetal spine at the level of stomach and the umbilical vein.

Diagnosis of IUGR

FL/AC ratio (expressed as femur length/abdominal circumference8x100) was determined to diagnose IUGR. The normal value for this ratio ranges from 22+/-2% in second half of pregnancy i.e. from 21 to 42 weeks ^{3, 4} (hadlock et.al, lan Donald). Patients with FL/AC> 23.5 were taken as IUGR^{3, 5} (lan Donald, padubidri and anand et. Al.).

Placental Measurement

The placental length and width were measured respectively in longitudinal and transverse section of placenta by taking the maximum dimension of chorionic surface from one edge of placenta to another. The placental diameter was calculated by taking the average length and width. The measurements were obtained taking care not to include retro placental complex or the myometrium. The results were then discussed with other comparable studies. After discussing the result final conclusions of the present study were made.

 

OBSERVATION AND RESULTS

Placental diameter and gestational age

The mean value of placental diameter in millimetres at different gestational age in weeks is shown in table 1. It was observed that there was increase in placental diameter with increasing gestational age.

 

Table 1: Showing mean value of placental diameter in millimeters at different gestational in weeks

 

The mean value of placental diameter increased from 70.75mm at 13 weeks of gestation to 252.2mm at 40 weeks of gestation.

Femur length (FL) and gestational age

The mean value of femur length in millimeters at different gestational age in weeks is shown in table 2. It was observed that there was increase in femur length with increasing gestational age.

 

Table 2: showing mean value of femur length in millimeters at different gestational age in weeks

 

Abdominal circumference (AC) and gestational age

The mean value of abdominal circumference in millimeters at different gestational ages in weeks is shown in table 3. It was observed that that there was increase in abdominal circumference with increasing gestational age.

 

Table 3: Showing mean value of abdominal circumference in millimeters at different gestational age in weeks

 

The mean value of abdominal circumference increased from 127.2mm at 18 weeks of gestation to 350mm at 40 weeks of gestation. In present study, 5 cases of IUGR pregnancy were found sonographically one case each at 32, 35 and 37 weeks of gestation and two cases at 39 weeks of gestation. The value of placental diameter, femur length and abdominal circumference in millimetersfor IUGR pregnancy are shown in table 4

 

Table 4: Showing values of placental diameter, femur length and abdominal circumference in millimeters for iugr pregnancy

 

It was observed that compared with normal pregnancy, the values of placental diameter and abdominal circumference were comparatively less for IUGR pregnancy at the corresponding gestational age Comparing and on analysis the p value for all the three parameters were calculated and it was less than 0.001, which suggests that it is highly significant. That means there is a high degree and significant correlation between placental diameter, femur length and abdominal circumference in mm with gestational age in weeks.

 

DISCUSSION

Placental diameter

The placental diameter increased progressively with increasing gestational age. It was 70.75mm at 13 weeks of gestation. It increased to 252.2mm at 40 weeks of gestation. Ghosh et. Al. in their study reported increase in placental diameter with advancing pregnancy. However no data is available on this aspect of comparison. The femur length increased progressively from 13^th week to 40^th week of gestation. The mean femur length at 13^th week was 9mm and at 40^th week its 76.5mm which are comparable to studies done by hadlock et al in 1982. Similarly the abdominal circumference increases with the gestational age in weeks and our results are comparable to studies done y hoffbaeur et.al in 1979 and hadlock et.al in 1982.

 

SUMMARY AND CONCLUSION

In the present study, the variation in placental size with gestational age on ultrasonography was studied in 100 pregnant women between 13^th and 40^th week of gestation.

1. The placental diameter increased progressively with gestational age.
2. The mean value of placental diameter increased from 70.75 mm at 13 week of gestation to 225.2mm at 40 weeks of gestation.
3. The placental thickness in millimeters almost matches with the gestational age in weeks from 13 to 40 weeks. It can be used as additional parameters along with fetal parameters for estimating gestational age of fetus in instances when duration of pregnancy is not known or uncertain.
4. There was a significant positive correlation between placental diameters with gestational age by sonography.
5. In the present study, 5 cases of intrauterine growth reduction (IUGR) pregnancy were found sonographically one case each at 32, 35, 37 weeks of gestation and two cases at 39 weeks of gestation.
6. The placental parameters were comparatively less in IUGR pregnancy.
7. Determination of placental diameter should be carried out on a regular basis during routine obstetrics scans as it may be helpful in diagnosis of abnormal placentas and can provide an insight into prenatal life which can be helpful in neonatal care and the findings can provide a record which obstetricians and pediatricians can use to plan the future of the mother and child.

 

 

 

 

REFRENCES

1. Indian Journal of Public health research and development Year: 2010, Volume 1, Issue: 2 Pg-23 to 26 Ultrasonography of normal human placenta in different gestational ages Devi C.K. Lakshmi, Kumar L.nanda, Reddy J. Vasudeva.
2. Textbook of obstetrics: D.C. Dutta, 6^th edition, pg 464
3. Ian Donald’s Practical obstetric problem, 6/e- Page 337 Renu misra
4. A Date-Independent Predictor of intrauterine Growth Retardation: Femur length/abdominal circumference ratio; Hadlock et. al AJR141:979-984, 1983

Textbook of obstetrics-V. Padubiri and Ela Anand 2006 First edition pg 150.

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