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How do you recognize premature labor?
Last reviewed: 03.07.2025
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Diagnosis of premature birth
A distinction is made between threatening, incipient, and already begun premature labor.
In case of threatened premature labor, a woman complains of pulling, aching pains in the lower abdomen and lower back, a feeling of pressure, distension in the vagina, perineum, rectum, possibly frequent painless urination, which may be a sign of low position and pressure of the presenting part. Regular labor activity is absent, individual contractions of the uterus are recorded. Excitability and tone of the uterus are increased.
Vaginal examination: the cervix is formed, the length of the cervix is more than 1.5–2 cm, the external os is either closed or, in women who have given birth before, allows the tip of a finger to pass through, in some cases the lower uterine segment is stretched by the presenting part of the fetus, which is palpated in the upper or middle third of the vagina.
Ultrasound: the length of the cervix is 2–2.5 cm, the cervical canal is dilated to no more than 1 cm, the fetal head is located low.
Dynamic monitoring of the pregnant woman by one specialist is important, if possible, due to the individual characteristics of the cervix of each woman. If there is dynamics in the form of softening, shortening of the cervix, as well as the condition of the external, internal os or cervical canal, we are talking about the beginning of premature labor.
When premature labor begins, cramping pains in the lower abdomen and lower back or regular contractions with an interval of 3 to 10 minutes are noted. During a vaginal examination, the length of the cervix is less than 1.5 cm, the cervical canal is passable for a finger, as labor progresses, the cervix smooths out and opens.
Premature labor that has begun is characterized by regular contractions and cervical dilation of more than 3–4 cm. As a rule (but not necessarily), amniotic fluid leaks. Regular uterine contractions are recorded every 3–5 minutes.
The diagnosis is based on both the complaints of the pregnant woman and an objective assessment of the contractile activity of the uterus and the dynamic change in the condition of the cervix during a vaginal examination.
In cases of threatened or beginning premature labor, tactics aimed at prolonging pregnancy are possible.
In the event of premature labor, leakage of amniotic fluid, signs of infection, or the presence of severe extragenital pathology, active labor management tactics are advisable (refusal to further prolong the pregnancy).
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Special research methods
Actions to take when examining a pregnant woman who presents with complaints of nagging pain in the lower abdomen and lower back.
- Eliminate factors that lead to complications of premature birth:
- premature rupture of membranes (smear for elements of amniotic fluid, amnitest);
- premature detachment of a normally located placenta (nature of discharge, detection of local tone and pain, ultrasound confirmation);
- placenta previa according to ultrasound data.
- Conduct an assessment of the condition of the fetus (based on functional diagnostic methods - ultrasound, CTG):
- listen to the fetal heartbeat;
- exclude fetal developmental abnormalities;
- assess the amount of amniotic fluid (polyhydramnios, oligohydramnios);
- accurately determine the gestational age and body weight of the fetus, compare weight and height indicators to identify intrauterine growth retardation of the fetus;
- perform a non-stress test (CTG data) at a pregnancy term of more than 32 weeks.
- Identify or rule out signs of infection by:
- urine culture to detect asymptomatic bacteriuria;
- bacteriological examination and PCR of vaginal and cervical canal discharge (detection of group B streptococci, gonorrhea, chlamydial infection);
- microscopy of vaginal smear (detection of bacterial vaginosis, vulvovaginitis);
- thermometry, clinical blood analysis with the study of the leukocyte formula for the diagnosis of chorioamnionitis. The length of the cervix, measured during ultrasound with a transvaginal sensor, allows us to identify the risk group for premature birth.
Up to 20 weeks of pregnancy, the length of the cervix is very variable and cannot serve as a diagnostic criterion for the occurrence of premature birth in the future. At 24–28 weeks, the average length of the cervix is 45–35 mm, at 32 weeks and more – 35–30 mm. Shortening of the cervix to 25 mm or less at 20–30 weeks of pregnancy is a risk factor for premature birth.
Differential diagnosis of premature birth
In cases of threatened premature birth, the main symptom of which is pain in the lower abdomen and lower back, differential diagnostics are carried out with pathology of the abdominal organs, primarily with pathology of the intestine (spastic colitis, acute appendicitis), with diseases of the kidneys and urinary tract (pyelonephritis, urolithiasis, cystitis).
If pain occurs in the uterine area, it is necessary to exclude necrosis of the myoma node and failure of the uterine scar.