Objective To establish reference intervals for fetal left and right lung areas and lung area to head circumference ratio (LHR). Methods In 501 cases of normal singleton pregnancy between 12 to 40 weeks, the left and right lung areas were measured respectively by ultrasound in the standard four chamber view, using manual tracing of the limits of the lungs. The left and right LHR were calculated when head circumferences were divided by the left and right lung area. Results Normal fetal reference intervals of left and right lung areas and LHR with gestational age were obtained. Fetal left and right lung areas and LHR increased with gestational age. Conclusion Fetal left and right lung areas and LHR values positively correlated with gestational age in normal pregnancy. Normal reference intervals of fetal LHR for every gestational age are valuable for evaluation of prognosis of fetal diaphragmatic hernia and other pulmonary peripheral space-occupying lesions.