ULTRASONOGRAPHIC CRITERIA FOR CORRELATION BETWEEN GESTATIONAL AGE AND PLACENTAL THICKNESS

Abstract

The placenta is primarily a fetal organ, its size a reflection of the health and size of the fetus. The normal placenta is a discoid organ, but at high altitudes it is ovoid as a rule of thumb, it should be approximately equal in thickness (in millimeters) to the gestational age in weeks =+/-10 mm. The term placenta should generally not thicker than 4.0 cm, although some exceptions do occur- Placental volume in the second trimester has been shown to be an accurate predictor for abnormal fetal outcome, but the method of measurement is complex and not widely adopted. Placenta reaches its ultimate thickness and shape in the 16th week of gestation but growth in diameter continues until the end of the third trimester. The placenta is a hemochorial tissue which provides oxygen and nutrient exchange between the fetus and mother. At no stage of pregnancy was the normal placenta greater than 4 cm in thickness. Potential pitfalls in measuring placental thickness are addressed, as well as potential causes of aberrations in placental thickness. Aim: The study was conducted with the aim of evaluating placental thickness, as a parameter for estimating gestational age of the fetus. The study was conducted on the pregnant ladies in different gestational age in weeks for placental thickness. The purpose of study was to determine the ultrasonographic criteria for correlation between the gestational age and placental thickness. Placental thickness was measured and correlated with menstrual age. The placenta was demonstrated to increase in thickness with advancing menstrual age. The study was conducted on 500 pregnant women with different weeks of gestational age attending the ultrasound obs/gynae out patient clinic at maternity and children hospital Buraidah Al-Qasim Saudi Arabia and Afro-Asian institute of medical sciences Lahore Pakistan. The sample population was from different socioeconomic group. Ultrasound was done by using Toshiba Nemio-20and GE logic 200 with standard. Culvillinear probes. After estimating the BPD, HC, AC and FL the placental thickness was calculated for all gestational ages.

Results It was observed that the placental thickness gradually increased from 15.2mm at 14 weeks to 38.6 mm at 39 weeks .From 18 weeks to 39 weeks of gestation the placental thickness coincide almost exactly with the gestational age in weeks.

Conclusion: The measurement of the placental thickness is an important parameter for estimating gestational age along with other parameters especially in the 2nd and 3rd trimester what ever the age and parity of the mother is at the time of gestation.