Medical devices

1. An embryo transfer catheter having an elongate shaft comprising a first, inner layer of a polymeric material coextruded with a second layer of a polymeric material on an outside of the inner layer, the first layer being substantially free of gas bubbles, the second layer including fixed gas bubbles encapsulated by the polymeric material of the second layer to increase the visibility of the catheter under ultrasound imaging, the gas bubbles being in a region extending along the length of the elongate shaft of the catheter, and the first layer that is substantially free of gas bubbles being thinner than the second layer and forming an innermost layer of the elongate shaft of the catheter.

2. The embryo transfer catheter according to claim 1 , wherein the gas bubbles have a size in the range 1μ to 50μ.

3. The embryo transfer catheter according to claim 2 , wherein the gas bubbles have a size in the range 5μ to 10μ.

4. The embryo transfer catheter of claim 1 , wherein the gas bubbles have a size in the range 0.1μ to 300μ.

5. The embryo transfer catheter according to claim 1 , wherein the second layer forms an outermost layer of the elongate shaft of the catheter.

6. The embryo transfer catheter according to claim 1 , wherein the region including the gas bubbles extends around the entire circumference of the elongate shaft of the catheter.

7. The embryo transfer catheter according to claim 1 , wherein the region including the gas bubbles extends continuously along the length of the elongate shaft of the catheter.

8. The embryo transfer catheter according to claim 1 , wherein the gas bubbles are provided by gas filled polymer microspheres.

9. The embryo transfer catheter according to claim 1 , wherein the catheter has a bore extending along its length.

10. The embryo transfer catheter according to claim 9 , wherein the inner layer has an inner surface defining the bore of the catheter.

11. The embryo transfer catheter according to claim 9 , wherein the polymeric materials are transparent to the eye, and the density of the gas bubbles is such as to permit material within the catheter to be viewed by the eye.

12. The embryo transfer catheter according to claim 1 , wherein the region including the gas bubbles extends in a longitudinal stripe along the elongate shaft of the catheter.

13. An embryo transfer catheter having an elongate shaft of polymeric material, the shaft comprising an inner layer of a polymeric material and an outer layer of a polymeric material on an outside of the inner layer, the inner layer being substantially free of gas bubbles, the outer layer including fixed gas bubbles encapsulated by the polymeric material of the outer layer to increase the visibility of the catheter under ultrasound imaging, the gas bubbles being in a region extending along the length of the elongate shaft of the catheter, the outer layer being thicker than the inner layer, and the inner layer forming an innermost layer of the elongate shaft of the catheter.

14. The embryo transfer catheter according to claim 13 , wherein the region including the gas bubbles extends around the entire circumference of the elongate shaft of the catheter.

15. The embryo transfer catheter according to claim 13 , wherein the region including the gas bubbles extends continuously along the length of the elongate shaft of the catheter.

16. The embryo transfer catheter according to claim 13 , wherein the region including the gas bubbles extends in a longitudinal stripe along the elongate shaft of the catheter.

17. An embryo transfer catheter having an elongate shaft of transparent polymeric material, the shaft comprising an inner layer of a polymeric material coextruded with an outer layer of a polymeric material on an outside of the inner layer, the inner layer being substantially free of gas bubbles, the inner surface of the outer layer being covered by the inner layer, the outer layer including fixed gas bubbles encapsulated by the polymeric material of the outer layer to increase the visibility of the catheter under ultrasound imaging, the gas bubbles being in a region extending along the length of the elongate shaft of the catheter, the density of the gas bubbles being sufficiently low to enable visualization of an embryo in the catheter, the outer layer being thicker than the inner layer, and the inner layer forming an innermost layer of the elongate shaft of the embryo transfer catheter.

18. The embryo transfer catheter according to claim 17 , wherein the region including the gas bubbles extends around the entire circumference of the elongate shaft of the catheter.

19. The embryo transfer catheter according to claim 17 , wherein the region including the gas bubbles extends continuously along the length of the elongate shaft of the catheter.

20. The embryo transfer catheter according to claim 17 , wherein the region including the gas bubbles extends in a longitudinal stripe along the elongate shaft of the catheter.

21. An embryo transfer catheter having an elongate shaft of polymeric material, the shaft comprising three coextruded layers each of a polymeric material, the three coextruded layers comprising an inner layer, an outer layer and a middle layer between the inner and outer layers such that the inner and outer surfaces of the middle layer are covered by the inner and outer layers, respectively, the inner and outer layers being substantially free of gas bubbles, the middle layer including fixed gas bubbles encapsulated by the polymeric material of the middle layer to increase the visibility of the catheter under ultrasound imaging, the gas bubbles being in a region extending along the length of the elongate shaft of the catheter, the inner and outer layers being thinner than the middle layer, and the inner and outer layers forming inner and outer surfaces, respectively, of the elongate shaft of the catheter.