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ObjectiveTo generate physical models of fetuses from images obtained with three-dimensional ultrasound (3D-US), magnetic resonance imaging (MRI), and, occasionally, computed tomography (CT), in order to guide additive manufacturing technology.Materials and MethodsWe used 3D-US images of 31 pregnant women, including 5 who were carrying twins. If abnormalities were detected by 3D-US, both MRI and in some cases CT scans were then immediately performed. The images were then exported to a workstation in DICOM format. A single observer performed slice-by-slice manual segmentation using a digital high resolution screen. Virtual 3D models were obtained from software that converts medical images into numerical models. Those models were then generated in physical form through the use of additive manufacturing techniques.ResultsPhysical models based upon 3D-US, MRI, and CT images were successfully generated. The postnatal appearance of either the aborted fetus or the neonate closely resembled the physical models, particularly in cases of malformations.ConclusionThe combined use of 3D-US, MRI, and CT could help improve our understanding of fetal anatomy. These three screening modalities can be used for educational purposes and as tools to enable parents to visualize their unborn baby. The images can be segmented and then applied, separately or jointly, in order to construct virtual and physical 3D models.

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Monozygotic (MZ) twins are relatively rare, with an incidence worldwide of about 0.40-0.45% after non-stimulated in-vivo conception 1 . The rate of MZ twinning after assisted reproductive technology (ART) is estimated to be between two and 12 times higher than for natural conception 2 . Higher-order multiple pregnancies carry significantly increased risks of fetal morbidity and mortality compared with the baseline risks of a twin pregnancy. Additional risks are also associated with monochorionicity. Simultaneous division of two transferred embryos in ART is a rare event (< 0.16% of all pregnancies) and only a few cases have been reported in the literature 3 . Several reports refer to higher-order multiple pregnancies as a result of the increasing use of ART in recent years, including quadruplet pregnancies 4 . However, embryo reduction is performed in most cases and good outcomes in higher-order multiple pregnancies from ART are scarcely reported. We present here a case of successful pregnancy after simultaneous division of two transferred embryos, resulting in two sets of monochorionic diamniotic twin pregnancies. Three-dimensional (3D) virtual and physical models of the pregnancy were created using prenatal ultrasound and magnetic resonance imaging (MRI) data.A 32-year-old Caucasian woman with an unremarkable medical history, who failed to conceive after 3 years of trying, was diagnosed with bilateral endometrioma, peritoneal endometriosis and right tubal dilatation on MRI. The couple was offered ART. In the first cycle of in-vitro fertilization (IVF), eight oocytes were collected. This first attempt was unsuccessful and embryo transfer resulted in miscarriage after 4 weeks. A new attempt at IVF was made 6 months after the first cycle. Eight oocytes were obtained and fertilized, resulting in three embryos. Two blastocysts were transferred. Beta-human chorionic gonadotropin was 1612 IU 13 days after transfer. Transvaginal ultrasound examination at 6 weeks showed two intrauterine sacs, each containing two embryos. The couple was informed on the maternal and fetal risks of a quadruplet pregnancy and counseled on the possibility of fetal reduction, which was declined. During first-trimester ultrasound examination, anatomy of all four fetuses was apparently normal ( Figure S1 and Videoclips S1-S3). Cervical cerclage was performed at 16 weeks for the prevention of preterm delivery and vaginal progesterone was prescribed at 24 weeks. MRI was performed at 26 weeks (Figure 1a and Videoclip S4) due to difficulty in evaluating complete fetal anatomy with ultrasound, and 3D virtual and physical models were constructed using the data (Figure 1b-d and Videoclips S5 and S6). Cesarean section was performed at 32 weeks due to uterine contractions and dyspnea, delivering four male babies (Table 1). Apgar scores at 1 and 5 min were 9 or 10 in all neonates. Two neonates were discharged from the hospital 34 days after delivery and the other two at 36 days after delivery ( Figure S2). MZ twinning following IVF was first reported in ...