OBJECTIVE To obtain normal values for intracardiac pressures in the human

fetus.

DESIGN Intracardiac pressures were measured directly in the four chambers of the human fetal heart during clinically indicated invasive obstetric procedures.

SETTING Department of fetal medicine in a tertiary referral centre.

PATIENTS 39 fetuses between 16 and 29 weeks of gestation.

RESULTS The ventricular waveforms obtained were similar to those found in postnatal life. There was an increase in ventricular systolic and end diastolic pressures with advancing gestation. There was no difference between left and right ventricular pressures. Atrial pressures were equal and remained constant in the gestational age range studied.

CONCLUSIONS Fetal cardiovascular pressure measurements in the normal fetus assist in understanding the fetal circulation, and provide a basis for the assessment of cases of congenital heart disease that may be amenable to intrauterine treatment.