Generally women are constipated than men owing to their pelvic shape and cyclical hormonal changes. Pregnancy puts pressure on the abdomen cavity which can cause the veins near the anus to swell. So piles during pregnancy is something common.In most cases, after the pregnancy, the Hemorrhoid or piles disappears.
The pressure within the abdominal cavity increases as the pregnancy progresses. The baby's weight and size in the latter part of pregnancy puts direct pressure on the rectum and anal cushion. So the rectal veins can not drain easily causing back flow pressure which in turn dilates the veins and cause piles! The direct pressure on the rectum can lead to constipation which adds to the problem.
After the delivery of baby naturally, the pressure relieved and piles usually disappears. But during the natural passage of baby through the birth canal because of the baby size the tissues in and around perineum and anal canal are damaged mechanically. This in turn can cause piles then or in future. Most of the time the healing leads to Fissure in Ano (like fissures in mouth/lips) rather than Piles. Sometimes the obstetrician makes a knife cut near the perineum for easy passage of baby then suture the wound called Episiotomy. This while healing can lead to scar formation and narrowing of anal canal.This may cause Anal fissure and constipation which in future can lead to piles.
Pregnancy is natural. A normal physiology, bringing happiness so don't worry about the piles. Just keep your bowel soft and regular by fibre rich diet and if needed take mild laxatives advised by your physician. Enjoy the Pregnancy!