The goal of this observational study is to evaluate the outcomes of twin pregnancies referred to our center, in order to understand whether the use of different guidelines over time, with more systematic follow-up timing, has improved their management by reducing adverse events. All this would provide us with useful information for a better understanding of the effects of twinhood on pregnancy outcomes, so that we have more accurate information in counseling with patients.

The study is retrospective and prospective. Patients for whom twin pregnancy was monitored at the outpatient clinics of the division of Obstetrics and Prenatal Age Medicine, a regional referral center for the management of complicated pregnancies, will be enrolled.

Only those patients for whom the delivery was carried out at the same facility will be considered. This first phase will be necessary to obtain specific information about the complication rate and course of twin pregnancies that over the past 15 years (2005 to present) have been afferent at our facility. All patients will undergo the ultrasound evaluations required by the normal care protocols for twin pregnancies (biweekly checks if monochorionic or monthly if bicorionic) until 2026.

In addition to the standard ultrasound monitoring, an instrumental assessment will then be performed by means of the USCOM 1A ® technique, an ultrasound instrument that, by inputting the patient's height and weight, is able to calculate, thanks to internal algorithms, the diameter of the aortic valve and the blood flow through the valve itself. In addition, the peak pulsatility of the maternal ophthalmic artery will be assessed by Doppler ultrasound technique, which appears to be predictive of the risk of developing preeclampsia. In addition to the normal ultrasound evaluation provided by the current care procedure, an echocardiographic acquisition of the fetal heart by STRAIN technique will be performed.

Two-dimensional strain is based on the acquisition of a typical myocardial pattern (called finger print), which can be followed during the cardiac cycle. In other words, the software recognizes a small piece of tissue, evaluating its strain. Because of its angle-independence, two-dimensional strain allows global and segmental assessment of myocardial contractility, both longitudinal and radial. In these patients, strain would have the ability to detect a contractility deficit evidenced by a reduction in peak systolic strain and strain rate, which, as already demonstrated in adults, distinguishes areas of increased fibrosis, myocyte loss, and myocardial fiber reorganization. Strain may also be useful in prognostic stratification of heart failure, distinguishing fetuses with particularly impaired contractile capacity.

Inclusion Criteria:

• Age > 18 years
• Twin Pregnancy
• Ultrasound monitoring and delivery occurred at Policlinico S Orsola in Bologna, Italy
• Written informed consent form obtained from the patient

Exclusion Criteria:

• Completion of delivery at another facility
• Desire to undertake the Voluntary Interruption of Pregnancy
• Refusal to undergo instrumental monitoring and subsequent follow-up at our center

The study population will consist of patients with twin pregnancies, regardless of chorionicity, who access the Pregnancy at Risk outpatient clinic at our center to perform the specific diagnostic care pathway.