Asymptomatic Bacteruria is defined as the presence of positive urine culture in a woman without signs of urinary infection. This condition, which in the general population does not require attention, requires early treatment in pregnancy and follow-up until birth.
The prevalence of non-symptomatic bacteriuria (bacteria in the urine) in pregnancy is the same as that of non-pregnant women: 4-7%. However, events of recurrent bacteriuria are more common in pregnancy. Risk factors for asymptomatic bacteriuria are: age, multiple pregnancies, sexual activity, diabetes, low socioeconomic status, women with Sickle cell trait, and women with history of urinary tract infection.
UTI (urinary tract infection) is the most common infection in pregnancy. Approximately 20% -40% of women with non-symptomatic bacteriuria at the beginning of pregnancy will develop urinary tract infection, including kidney infection (Pyelonephritis), if they are not treated, compared to women without bacteriuria (i/e sterile urine), of whom 1% to 1.5% will develop kidney infection. It is important to note that early treatment of asymptomatic bacteriuria has been shown to prevent most cases of complex UTI- Pyelonephritis. In cases of resistant non-symptomatic bacteriuria, there is a higher risk of developing urinary tract infection, and failure to treat non-symptomatic bacteriuria may indicate that the bacteria is located in the higer part of the urinary tract (kidneys) than in the lower part (bladder).
There is a well known connection between Pyelonephritis and preterm delivery. As early as 1959, Kass reported that treatment with asymptomatic bacteriuria significantly reduces the incidence of premature birth. In addition, because kidney infection in pregnancy is also a dangerous condition for the mother (and not only for the pregnancy), it seems reasonable to screen urine for bacteria during the first weeks of pregnancy and to treat any case of asymptomatic bacteriuria.
The reason for the prevalence of urinary infections in pregnant women is the expansion of the urinary ureters and renal pelvis, in addition to a decrease in urethral peristalsis. These changes start from the seventh week of pregnancy, partly because of an increase in estrogens. The changes worsen as the pregnancy progresses (probably because of uterine pressure on the ureters). The muscle tone of the bladder (Detrusor) decreases in pregnancy, so that the capacity of the bladder multiplies itself. Usually the changes are more pronounced on the right side of the urinary tract and more common in the first pregnancy. It should be noted that the situation returns to its predicament about two months after birth.
According to the worldwide guidelines, every woman should have a urine test (general and culture urine test) in the first and last trimester of pregnancy. The frequency of urine tests is not determined, but the first test will be performed in the first trimester.
As noted, it is important to distinguish the status of non-symptomatic bacteriuria in pregnant women from most other conditions (eg postmenopausal women, people with a permanent catheter, young women wo are not pregnant), in whom there is no need for evaluation or treatment.
If the pregnancy urine test results in bacterial growth, antibiotics should be given. The goal of the treatment is to obtain sterile urine throughout the pregnancy and to prevent the complications described above.
The most common treatment options in pregnancy are: Resrim (Trimethoprim / Sulphamethoxazole), Nitrofurantoin, Amoxicillin, Cefalexin, Augmentin (Amoxycillin / Clavulanic acid), Monolrol (Fosfomycin) and Zinnat (Cefuroxime).
Resrim is not suitable for use during the last weeks of pregnancy because it may worsen the newborn's jaundice (neonatal hyperbilirubinemia). It is also advisable to avoid Trimethoprim at the beginning of pregnancy because it is a folic acid inhibitor. Other drugs not recommended for pregnancy are tetracyclines and quinolones.
As for the duration of the treatment, there are no studies that examined the use of oral antibiotics in a single dose or for 3 days of treatment. In general, treatment with one single dose is less effective than a few-day treatment, and not acceptable in pregnancy. Three days of treatment seem to be effective, but there is enough evidance to support that. The latest guidelines recommend 3-7 days of treatment.
Repeated urine culture is mandatory for 1 to 2 weeks after treatment and once a month until pregnancy is over. If the tests reveal bacteriuria again, re-treatment is necessary. It is also important to avoid bladder catheterization at delivery. If there are reccurent events , a post-natal evaluation should be performed. In addition, it is recommended to consider antibiotic prophylaxis until birth (Nitrofurantoin 100-50 mg every night), but note that the drug is prohibited before delivery, and if there is a suspected lack of G6PD. Another option is Cephalexin 500-250 mg every night.