The aim of this prospective longitudinal study was to investigate the relationship between placental thickness during the second and third trimesters and placental and birth weights.

The investigator will make certain that the appropriate informed consent process is in place to ensure that potential research subjects, or their authorized representatives, are fully informed about the nature and objectives of the study, the potential risk and benefits of study participation, and their right as research subjects.

All laboratory specimens, evaluation forms, reports, video recordings, and other records that leave the site will not include unique personal data to maintain subject confidentiality.

All patients provided an informed written consent after they were fully instructed about the investigation.The study was approved by ethical committee of Ain Shams University.

All recruited women were observed at the 1st trimester screening at antenatal clinic and assessed for baseline demographic and obstetric data including age, parity, body mass index (BMI) and past medical events. Smoking, alcohol and drug use were also determined.

At second and third trimester (15-20 and 30-34 weeks of gestation respectively), the maternal weight, weight gain, BMI, BMI gain and data of ultrasound examination were recorded. At the time of delivery after assessment of maternal weight as mentioned above, the birth weight (in grams), fetal sex, and mode of delivery were taken.

All pregnant women underwent ultrasound evaluation of placental thickness at the time of second trimester (15-20 weeks of gestation) as well as third trimester (30-34 weeks of gestation).

All sonographic examinations were performed trans-abdominal using a Medison X4 ultrasound machine Trans abdominal4.0 megahertz (MHz) probe at The Special Care Center for Fetus Unit at Ain Shams University Maternity Hospital.

The placental thickness was measured by placing the ultrasound transducer perpendicularly to the plane of the placenta, in the area of the cord insertion, near the mid-placental portion as described by Hoddick et al

Each evaluation was performed by one of two experienced sonographers of our hospital with minimum inter- and intra-observer variability.

After delivery, the placenta was weighed in grams as previously described by Azpurua et al.

Fetal weight (primary objective) and neonatal status and morbidity including baby Apgar scores, fetal distress or fetal death and admission to the neonatal intensive care unit were also determined. All the examinations and data recording were performed by two senior resident physicians.(secondary objective)

Inclusion Criteria:

1. patient Aged between 18 and 45 years.
2. singleton viable pregnancy.
3. non scared uterus.

Exclusion Criteria:

1. systemic illness (DM,Hypertension, renal disease, liver disease, sickle cell disease)
2. known congenital fetal anomalies.
3. multiple pregnancy.
4. intra uterine fetal death.
5. anatomical defect of pregnant uterus
6. abnormally located placenta or placental anomalies
7. morbid obesity
8. missing records
9. unwilling to incorporate in the study.

uncomplicated pregnant women who will attend the outpatient clinic at Ain Shams University Maternity Hospital

adverse event data collection was about 9 months ( time between starting antenatal care and end delivery )