Placenta accreta is a relatively rare event, in which the placenta is abnormally implanted into the uterine myometrium. The most significant complication is intense bleeding, mainly during labor. The incidence of placenta accreta increased during the last years due to the increase in cesarean delivery rate, which is the main risk factor. Pre-cesarean diagnosis of placenta accreta may improve surgical outcome. Early diagnosis allows appropriate preparation of multidisciplinary team (including, among others; OB-GYN, urologists, anesthesiologists, neonatologists) and massive blood products. Pre-cesarean diagnosis is based on imaging, mainly ultra-sound. This modality has significant false positive rate which may result in extreme sources investment and even indicated pre-term labor, in vain. Volatolome is a complex of volatile markers emitted in several processes in the human body and collected from breath, skin, urine, blood, feces and more. This profile may be used to identify volatile markers for specific medical conditions. NA-NOSE is an electronic device knowing to identify differences in the Volatolome between "healthy" and "sick" subjects. The objective of this study is to identify specific volatile profile for placenta accreta which will help to distinguish between women with placenta accreta and those without.

Pregnant women with clinical risk factors for placenta accreta will perform targeted sonographic evaluation for detection of placenta accreta features, according to a standard protocol. Of those with clinical and sonographic risk factors who will agree to participate in the study, will be asked to breathe through a collection device (NA-NOSE) for "lung wash". The participant will be instructed to inhale through the device and exhale to the ambient air for about 3 minutes. After the lung wash step, the collector will inform the participant that she is about to start filling the collective bags. At the end of a regular breath, after exhaling, the collector will ask the participant to take a deep breath so the full volume of the lungs is filled, and then exhale until both the dead space bag and collection bag are full. After filling the first bag, a second bag will be placed and the participant will be asked to repeat the act. In addition, a venous blood sample of 8-10 ml will be taken from each participant.

The samples will be transferred to the Department of Chemical Engineering and Russell Berrie Nanotechnology Institute, Technion-Israel, Institute of Technology. The samples will be analyzed to determine the nature and composition of the volatile biomarkers in the related breath and blood samples.

In this way, the investigators will identify among women who have clinical and sonographic risk factors for placenta accreta, those biomarkers distinguishing women with placenta accreta (group 1) from those who will not have placenta accreta at birth (group 2).

Inclusion Criteria:

1. Pregnancy > 28 weeks of gestation.

2. Agreement to participate and sign an informed consent.

3. Ability to give breath and blood samples.

4. Risk factors for placenta accreta:

   1. Placenta previa.

   2. Previous 1 or more cesarean sections with placenta in the scar area.

   3. Previous uterine procedures (myomectomy, curretage) and sonographic suspicion of abnormal placentation.

      - Exclusion Criteria: None

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Pregnant women, 28 weeks of gestation or more, with known risk factors for placenta accreta referred to our institute to perform an ultrasound scan for detecting abnormal placentation.

Decision regarding IPD sharing, will be taken later.