Sometimes passing urine frequently can be a sign of an infection in the bladder, known as 'cystitis' or a 'urinary tract infection' (UTI). Other signs of cystitis can be a burning or stinging sensation when urinating, a constant ache in the lower belly, headache, vomiting and / or a fever or chills. If the infection has moved up into the kidneys, called 'pyelonephritis', the woman may feel constant backache across the middle and sides of her back, at waist level. She may also see blood in the urine making it look pink, red or brown.
A urine infection after the 20th week of pregnancy may stimulate premature labour. In some cases the woman will be unaware of having a urine infection because she does not have the 'typical' symptoms of cystitis. She may simply complain of moderate lower abdominal pain, a fever or the mild regular contractions of the early premature labour. Your caregiver would diagnose the infection after sending a urine test to the pathologist. You would probably need a course of antibiotics in these circumstances.
About 5 -10 % of women (pregnant and non pregnant) have what is called 'asymptomatic bacteriuria'. Put simply this is bacteria growing in the bladder without the women being aware of any symptoms.
In non-pregnant women this tends not to cause any problems. In pregnant women the pregnancy hormone progesterone relaxes the bladder and the ureters. The baby often compresses these organs causing the urine to sometimes reflux back up to the kidneys as well as pool in the bladder. This encourages bacteria to multiply, sometimes causing an infection. Pregnant women can also have extra glucose present in their urine. This is normal due to the efficient functioning of the kidneys, spilling glucose into the urine from the blood before the body can use it for energy (this is not a sign of diabetes in pregnancy). Glucose can also contribute to promoting a bladder infection.
If the bacteriuria is not treated, about 20 - 30 % of pregnant women can develop an infection later in the pregnancy, possibly leading to premature labour. It is for this reason that many caregivers will send off a specimen of urine for testing at the first antenatal visit. You can read more about what to expect at your first antenatal visit in Class B. If bacteria are present they will probably suggest a course of antibiotics to treat it. Some women will choose to only accept antibiotics if they actually develop an infection later in the pregnancy. You should discuss this with your caregiver.
The most common bacterium that causes bladder infections is one called 'E. coli'. E, coli is a bug that is present in large quantities in the bowel. The bacteria may be transferred to the urethra and into the bladder through wiping the genitals from 'back to front' (or sometimes with sexual activity). Another organism that can be present is one called 'Group B streptococci' (also known as 'GBS' or 'Group B Strep'). This organism can also be transferred to the bladder from the vagina or bowel.
For a small number of women, Group B Streptococci can cause an infection in the uterus after the waters break. The presence of this bacterium is often looked for later in the pregnancy with a vaginal swab. You may wish to read more on this in Group B strep.