Objective To establish reference intervals for fetal heart stroke volume and cardiac output with gestation. Methods

Objective To determine the potential value of measuring the placental volume at 11 to 13 + 6 weeks of gestation in screening for chromosomal defects. MethodsThe placental volume was measured using threedimensional ultrasound in 500 consecutive singleton pregnancies immediately before chorionic villus sampling for fetal karyotyping at 11 to 13 + 6 (median, 12)

Objective To describe the morphology of the frontal bones and metopic suture at 9-34 weeks of gestation using three-dimensional (3D)

Objective

Index terms: MRI; temperature; safety; pregnancy; fetus SONOGRAPHY IS THE SCREENING METHOD of choice for fetal evaluation. However, there are cases in which alternative imaging is necessary to better evaluate congenital anomalies. Our laboratory and others have recently demonstrated the utility of ultrafast MR techniques such as half-Fourier single-shot turbo spin-echo (HASTE) to scan pregnant patients with sonographically anomalous fetuses (1-3). These sequences allow for images to be obtained in as little as 420 msec. This allows for fetal imaging to be performed without sedating either the pregnant patient or the fetus. One potential problem with a pulse sequence such as HASTE is that it requires a long train of refocusing echoes. These refocusing echoes have the potential to deposit much more heat than traditional spin-echo imaging.Though exposure of the patients to MRI can produce heat that is related to the radiofrequency pulses, MRI in pregnancy is thought to be safe for the fetus (4 -9). However, to our knowledge, studies have not been conducted in pregnant patients to verify that tissue heating is not occurring within the gravid uterus. Fluids, such as in the lens of the eye, are known to be relatively poor at dissipating deposited heat (10). Since the fetus essentially lies in a water bath, and since tissues dissipate heat by blood flow, it is possible that heat is accumulating in the gravid uterus during medical imaging.The reason this is of particular concern in pregnant patients is that the specific absorption rate (SAR) monitor, which documents the amount of energy deposited over time, is set for the weight of the patient. However, we actually are studying a much smaller patient (the fetus) in a highly conductive "salt-water" bath (amniotic fluid). In addition, the gravid uterus in the third trimester often fills the magnet bore: this will limit the amount of air flow through the bore and around the patient, thus potentially decreasing the ability of the patient to emit deposited heat to the environment.Both phase shift and T1-weighted sequences have been used successfully to measure temperature changes on a 1.5T scanner (11-13). However, studies in vivo are sensitive only to Ϯ2°C. We therefore need an animal model to evaluate whether significant heat deposition is occurring within the fetus or amniotic fluid during diagnostic MR scanning.Our current human fetal technique uses a scout view and three interleaved sequences (sagittal, axial, and coronal of the fetus). We hypothesize that clinically significant changes in temperature (greater than 1°C) will not occur at this exposure level. METHODSThis study was performed in three parts. Part 1 incorporated the use of a phase map in order to evaluate temperature changes occurring over an entire cross section of the gravid uterus. Part 2 consisted of direct measurements of temperature before and after diagnostic imaging by inserting copper-constantan temperature probes into the amniotic fluid, fetal brain, and fetal abdomen in pregnant minipigs. Part 3 ...

Objective To determine the potential value of measuring the gestational sac volume (GSV) at 11 to 13 + 6 weeks of gestation in screening for chromosomal defects. MethodsThe GSV was measured using three-dimensional (3D)

Objectives To examine the possible association of skull deformity and the development of the cranial sutures in fetuses with Apert syndrome.Methods

Objective To detect the presence of a gap between the fetal nasal bones at 11 to 13 + 6 weeks of gestation and to verify if this gap could lead to the erroneous diagnosis of absent nasal bone.Methods