METHODS
This prospective study was conducted in the Department of Obstetrics and Gynecology of Casilino Hospital in Rome, University of Tor Vergata. During the period between September 2016 and December 2017, we enrolled 395 patients not in labor.
We used strict inclusion and exclusion criteria. The inclusion criteria were:
Pregnant women were excluded if a maternal or fetal disease was present (diabetes, hypertensive disorders, IUGR, fetal malformation, etc.), if the pregnancy was the result of assisted reproduction therapy or if an elective C-section due to maternal request or breech presentation was scheduled.
Once the consensus was obtained, the anamnestic, anthropometric and demographic information were gathered. For each patient, the following parameters were collected: maternal age, height, weight, BMI, last menstrual period, gestational age corrected by first trimester ultrasound, obstetrical history and smoking.
An ultrasound exam was performed to measure the Pulsatility Index of Umbilical Artery, the Pulsatility Index of Middle Cerebral Artery and the Amniotic Fluid Index. Ultrasound examination was performed with a 3.5-MHz sector ultrasound transducer with the high-pass filter set at 100 Hz, in a moment of absence of fetal breathing and body movements. The umbilical artery, middle cerebral artery and uterine arteries were studied using colour Doppler according to the most modern standard protocol11Bhide A, Acharya G, Bilardo CM, Brezinka C, Cafici D, Hernandez-Andrade E et al. ISUOG practice guidelines: use of Doppler ultrasonography in obstetrics. Ultrasound Obstet Gynecol. 2013 Feb;41(2):233-39..
The CPR was calculated by dividing the Doppler indices of the middle cerebral artery (MCA) by the umbilical artery (UA). The UA and MCA pulsatility index (PI) was calculated according to a standard protocol22Bahlmann F, Reinhard I, Krummenauer F, Neubert S, Macchiella D, Wellek S. Blood flow velocity waveforms of the fetal middle cerebral artery in a normal population: reference values from 18 weeks to 42 weeks of gestation. J Perinat Med 2002; 30: 490 – 501..
The maternal haemodynamics was assessed by UltraSonic Cardiac Output Monitor (USCOM®, USCOM Ltd., Coffs Harbour, Australia). It is a non-invasive method that uses a continuous-wave Doppler to determine CO. It has demonstrated a comparable accuracy to invasive methods (Swan-Ganz catheter) and the USCOM measurements are well correlated with echocardiographic assessments33Bijl RC, Valensise H, Novelli GP, Vasapollo B, Wilkinson I, Thilaganathan B et al; International Working Group on Maternal Hemodynamics. Methods and considerations concerning cardiac output measurement in pregnant women: recommendations of the International Working Group on Maternal Hemodynamics. Ultrasound Obstet Gynecol. 2019 Jul;54(1):35-50.,44Kager CC, Dekker GA, Stam MC. Measurement of cardiac output in normal pregnancy by a non- invasive two-dimensional independent Doppler device. Aust N Z J Obstet Gynaecol. 2009 Apr;49(2):142-4.,55Namara H, Barclay P, Sharma V. Accuracy and precision of the ultrasound cardiac output monitor (USCOM 1A) in pregnancy: comparison with three-dimensional transthoracic echocardiography. Br. J. Anaesth. (2014) 113 (4): 669-676.. The measurements were performed by two trained operators, in the same room, under standardised conditions, with a patient in a semi-recumbent position, after she had rest in this position at least 15 minutes. Blood pressure was obtained before the hemodynamic measurement, using an automatic blood pressure monitor with the patient in a semi-recumbent position and using an appropriately sized cuff.
All the examinations were made from the suprasternal notch targeting the aortic valve using a 2.2 MHz Transducer, with patients in left lateral recumbent position.
We collected the following USCOM parameters: systolic blood pressure (SBP), diastolic blood pressure (DBP), systemic vascular resistance (SVR), systemic vascular resistance index (SVRI), cardiac output (CO), cardiac index (CI), stroke volume (SV), Smith-Madigan inotropy index (INO), flow time corrected (FTc), potential to kinetic energy ratio (PKR).
At the day of childbirth, we collected information about the labor and the delivery in order to identify any maternal or neonatal complications: gestational age at time of delivery, request of epidural analgesia, labor onset type (spontaneous or with induction), childbirth type (spontaneous, operative vaginal delivery, c-section) and any obstetrical indications, type of placental delivery, loss of blood and need of blood transfusion, neonatal sex, neonatal weight, 1-min Apgar and 5-min Apgar.
The induction of labor, if was required by internal routine antenatal management protocols, was performed with dinoprostone 10 mg vaginal insert and, after 24 hours, if the labor failed to start the vaginal insert was removed and after 30 minutes the oxytocin infusion started according to “low-dose” protocol66Fondazione Confalonieri Ragonese su mandato di SIGO, AOGOI, AGU. Induzione al travaglio di parto. 2016.
A delivery was considered “complicated” if just one of these conditions was present:
The PPH is defined as the loss of 500 ml or more of blood from the genital tract within 24 hours of the birth of a baby88Mousa HA, Blum J, Abou El Senoun G et al. Treatment for primary postpartum haemorrage Cochrane Database Syst Rev2014;(2)CD003249 Mousa HA, Blum J, Abou El Senoun G, Shakur H, Alfirevic Z. Treatment for primary postpartum haemorrhage. Cochrane Database Syst Rev 2014;(2):CD003249. Mousa HA, Blum J, Abou El Senoun G, Shakur H, Alfirevic Z. Treatment for primary postpartum haemorrhage. Cochrane Database Syst Rev 2014;(2):CD003249. The uterine atony is defined as the condition when the uterus fails to contract after the delivery of the baby99Breathnach F, Geary M. Uterine atony: definition, prevention, nonsurgical management, and uterine tamponade. Semin Perinatol. 2009 Apr;33(2):82-7.