[muchlove]

Globe-trotting actor Angelina Jolie not only showed off her swelling tummy, but also swelling veins during a visit to Haiti in the Caribbean.

And experts say it is actually Jolie's fat-free figure that has made the condition worse.

Just days after publicists confirmed that Jolie, a sponsor of several humanitarian causes, was expecting a child with her actor partner Brad Pitt, the A-list couple visited the sweltering capital of Haiti, Port au Prince.

While the almost rope-like appearance of the blood vessels was striking, medical experts said it was a common condition of pregnancy known as venous dilation.

Professor Michael Bennett from the Royal Hospital for Women said that venous dilation was caused by an expecting mother's increased blood supply, the extra body heat generated during pregnancy and being in a hot climate.

But the swelling would not be noticeable on someone with a lot of body fat.

"In somebody who is as slim as she is, you are likely to see the veins reasonably prominently in most circumstances when she is warm," Professor Bennett said.

"The pregnancy is producing heat and what she has to do physiologically is get that blood to the surface of her body to get rid of that heat."

Enlarging of the veins is also needed just to cope with the extra blood supply during pregnancy, Professor Bennett said.

"The blood volume goes up by close to 50per cent in the first 12 weeks of pregnancy," he said.

Jolie and Pitt have not revealed when their child is due, although she is said to be five months pregnant.

The pair were in Haiti on the invitation of Haitian-born hip-hop artist Wyclef Jean.