This study is to investigate if portal vein pulsatility fraction can be measured in pregnancy and if it increases during the course of pregnancy as would be expected by the physiologic increase in blood volume that happens during pregnancy. Portal vein pulsatility fraction is measured in non-pregnant controls and in women in the 1st, 2nd and 3rd trimester of pregnancy.

Inclusion Criteria:

• Ability to give informed consent
• American Society of Anesthesiologists (ASA) Class I and II
• Singleton pregnancy during 1st, 2nd or 3rd trimester or healthy non-pregnant females of childbearing age as controls

Exclusion Criteria:

• Inability to give informed consent
• Multiple gestation
• Significant co-morbidities (e.g. cardiac abnormalities, cardiac dysfunction, arrhythmias, severe asthma, renal insufficiency)
• High risk pregnancies (e.g. pre-eclampsia, gestational hypertension, HELLP, gestational diabetes)
• Body-Mass-Index (BMI) < 18kg/m2 or >40kg/m2

Pregnant women attending either the anaesthetic preassessment clinic or the obstetric ultrasound clinic at University Hospital Basel.

Non-pregnant healthy females fulfilling the inclusion criteria will be recruited by published advertisement at the University Hospital Basel.