This randomized, double blinded controlled trial included 1200 healthy primigravidae who attended an outpatient clinic at 16-20weeks of pregnancy. All women were randomly divided equally into two groups, group A(600 women) who received antichlamydial treatment in the form of azithromycin 1 gram single oral dose before 20 weeks of pregnancy and group B (600 women) who received no treatment(placebo). All participants were followed up for up to 6 weeks postpartum and observed for the development of preeclampsia.

Preeclampsia complicates approximately 5-8% of all pregnancies and is a major cause of maternal morbidity and mortality worldwide.Its progress differs among patients; most cases are diagnosed pre-term. Preeclampsia may also occur up to six weeks post-partum. The present study included 1200 primigravidae who attended the outpatient clinic of Ain Shams University maternity Hospital in Cairo, Egypt, for routine antenatal care between July 2016 and September 2017. The study was approved by the Ethics Committee of Ain Shams University Maternity Hospital in accordance with local research governance requirements. All participating women signed an informed consent form inclusion criteria were a primigravida, singleton pregnancy, maternal age 18-35 years, and pregnancy duration 16-20 weeks at the time of study inclusion. Exclusion criteria were Women with multi-fetal pregnancy, diabetes mellitus, chronic hypertension, or chronic renal disease.Computer based Randomization codes were placed in sequentially numbered, opaque, sealed envelopes by an observer, to be opened at time of enrollment by a pharmacist in Ain Shams University Hospital who prepared the study drug and had no further involvement with the patient's care. All data were analyzed before it was determined which group was received azithromycin and which was received placebo.

• Azithromycin 1Gm orally, single dose (Xithrone 500 mg two tablets, Amoun, Inc, Cairo, Egypt) Group (A) OR
• Matching placebo orally, single dose Group (B). Preeclampsia was defined in the terms of hypertension and proteinuria. The International Society for the Study of Hypertension (ISSH) defined preeclampsia as new hypertension and new proteinuria developing after 20 weeks of gestation and regressing remotely after delivery. Hypertension is defined as diastolic arterial blood pressure ≥90 mmHg on two or more consecutive occasions, at least 4 hours apart. Proteinuria is defined as ≥ +1 on dipstick test on 2 midstream urine collections more than 4 hours apart or 24-hour urinary protein ≥ 300mg. Severe preeclampsia was defined as follows: blood pressure >160/110 mmHg on two occasions at least 6 hours apart, proteinuria >5 gm/24 hours, oliguria < 500 ml/24 hours, thrombocytopenia < 100.000/ml, cerebral visual disturbances, epigastric pain, nausea and vomiting, impaired liver function of unclear etiology or the occurrence of complications as pulmonary edema, accidental hemorrhage or fetal compromise.

Inclusion Criteria:

• primigravida, singleton pregnancy, maternal age 18-35 years, and pregnancy duration 16-20 weeks at the time of study inclusion.

Exclusion Criteria:

• Women with multi-fetal pregnancy, diabetes mellitus, chronic hypertension, or chronic renal disease

double blind