Women with a history of a previous preterm birth at less than 37 weeks of pregnancy (due to spontaneous labor or premature rupture of membranes) may be offered a progesterone supplement, either as an injection or a vaginal gel, to prevent recurrent preterm labor. Progesterone supplementation is begun between 16 and 26 weeks of pregnancy and continued until 36 weeks. There is no evidence that this drug is effective in women with no previous history of preterm labor. In addition, it has not been effective in women with multiple gestations (eg, twins).
Although umbilical cord entanglement has been previously diagnosed with 2D ultrasound, it was difficult to confirm umbilical cord entanglement. Sherer et al. reported that they found umbilical cord entanglement on the transvaginal 2D color Doppler sonogram at 12 weeks' gestation [ 10 ]. However, it was difficult for the patient and her family to understand and accept that umbilical cord entanglement had occurred. Although the diagnosis can be made with 2D Doppler, 3D images provide clearer visualization of the cord entanglement and can help illustrate the problem to the parents. The cases using 3D images have been rarely reported and most 3D ultrasounds are conducted in the third trimester of pregnancy [ 11 - 13 ]. Yet, to date, our case is the first to diagnose umbilical cord entanglement by using 3D ultrasound at the first trimester. After delivery, the shape of umbilical cord entanglement was the same as that seen in the 3D ultrasound image. This finding supported a hypothesis that umbilical cord entanglement of monoamniotic twins occurred from the first trimester of pregnancy when the amount of amniotic fluid was relatively large compared to the size of the fetuses and they actively moved [ 14 ].