A delivery at 37 weeks of amenorrhea (WA) corresponds to a full-term pregnancy. Prematurity is defined as any birth occurring before this threshold. Recognizing the signs of labor at this stage means identifying a term labor, which changes the interpretation of each symptom.
The threshold of 37 WA and what it changes in the interpretation of symptoms
The distinction between 36 WA and 37 WA is not trivial. Before 37 WA, regular contractions or the loss of the mucus plug indicate a risk of premature birth and justify urgent care. After 37 WA, these same manifestations are physiological.
The mucus plug illustrates this shift well. Its loss typically occurs between 37 and 42 WA and can precede birth by a few days up to ten days. However, if it occurs before 37 WA, it should prompt an immediate consultation as it constitutes a potential sign of premature labor.
This time marker helps to better understand the signs of labor at 37 weeks without confusing them with a pathological situation. The difficulty for the pregnant woman lies in distinguishing a reassuring sign from a warning signal, and the date in weeks of amenorrhea serves as the first filter.
Contractions at 37 weeks: differentiating false labor from true onset
Contractions are the most anticipated sign but also the most misinterpreted at the end of pregnancy. Braxton-Hicks contractions, sometimes present since the second trimester, become more frequent at 37 WA. They remain irregular, mildly painful, and do not change the cervix.
Labor contractions follow an identifiable pattern: they come at regular intervals, gradually get closer together, and their intensity increases. The pain radiates from the back to the lower abdomen and does not subside with rest or position changes.
A common guideline used in maternity to decide when to go: regular contractions spaced five minutes apart or less, lasting for at least one hour, with an intensity that prevents normal conversation. Before reaching this stage, monitoring the regularity is more important than the raw pain.
What obscures the interpretation of contractions
Several factors can intensify contractions without actual labor being initiated. Dehydration, sustained physical activity, or a urinary infection can cause contractions that stop once the underlying cause is treated.
A lesser-known factor: high temperatures increase the number of births occurring between 37 and 38 WA. During heatwaves, contractions at 37 WA are statistically more frequent. Hydration and rest in extreme heat are not merely for comfort but are a documented obstetric precaution.
Loss of the mucus plug and rupture of the amniotic sac: two signals not to confuse
These two events are often conflated even though they have different meanings and urgencies.
- The mucus plug appears as gelatinous discharge, sometimes tinged with pink or brown. Its loss can be gradual or sudden. It indicates that the cervix is beginning to change, but labor may still be several days away.
- The rupture of the amniotic sac, whether it is a clear (abundant flow of clear and warm liquid) or a fissure (light but continuous leakage), requires a quick trip to the maternity ward. The baby is no longer protected in a sterile environment, and there is a risk of infection.
- Liquid losses that occur in small amounts and stop at rest are more likely to indicate urinary leaks related to the baby’s pressure on the bladder, which is common at this stage of pregnancy.
To distinguish amniotic fluid from urine, a simple test is to wear a clean panty liner for an hour. If the fluid is continuous, colorless, and odorless, the rupture of the sac remains the main hypothesis.
Physical signs associated with the baby’s descent into the pelvis
A few days to a few weeks before delivery, the baby descends into the pelvis. This repositioning changes the shape of the belly, which appears lower, and leads to a series of physical manifestations related to the new distribution of pressure.
- Breathing becomes easier as the pressure on the diaphragm decreases.
- The urge to urinate intensifies significantly, as the baby presses more on the bladder.
- Pain in the pelvis or legs may appear, sometimes as electric sensations, due to the compression of certain pelvic nerves.
- Intestinal transit may change: some women report more frequent or softer stools in the days leading up to labor.
The baby’s descent does not mean that labor is imminent. In a first pregnancy, it can precede birth by several weeks. For subsequent pregnancies, descent often occurs later, sometimes on the same day as labor.
When to go to the maternity ward at 37 weeks of pregnancy
Not all the signs described warrant the same level of response. The loss of the mucus plug, increased fatigue, or the descent of the belly are part of the normal process at the end of pregnancy and do not require an urgent trip.
Three situations justify a trip to the maternity ward: regular and close contractions that do not subside with rest, rupture or fissuring of the amniotic sac, and any bright red bleeding different from the pink traces associated with the mucus plug. In case of doubt about the nature of a discharge or the regularity of contractions, a call to the maternity ward allows for a phone evaluation before traveling.
At 37 WA, the baby has reached sufficient maturity to be born without specific neonatal care in the vast majority of cases. The goal is not to delay labor, but to present oneself at the maternity ward at the right time, neither too early (being sent home in false labor) nor too late.