The main function of the uterus during pregnancy is to house and nourish the growing fetus, so it is important to understand its structure and function and what changes the uterus can be expected to undergo during pregnancy.
How it’s made
The uterus takes different forms in different mammals, in the woman it is pear-shaped.
It is placed between the bladder and rectum and is covered by the wide ligament, which holds it in place in the center of the pelvis.
The wall of the uterus consists of 3 layers. Inside we find a thin layer called the endometrium, which thickens during the menstrual cycle in preparation for embryo implantation. The middle layer is a muscular wall. The outer layer of the uterus is a thin layer of cells, also known as the perimetrium, which is the continuation of the pelvic peritoneum.
The size of the uterus of a non-pregnant woman may vary. In a woman who has not had pregnancy, the average length of the uterus is about 7 centimeters. This increases in size to about 9 centimeters in a woman who has already had pregnancies (in the past). The size and shape of the uterus can change with the number of pregnancies and with age.
The uterus in pregnancy
During pregnancy, as the fetus grows, the size of the uterus will greatly increase. A measure to estimate the growth of the uterus and the fetus is the fund-symphysis: it is carried out by measuring with a tape measure, ie a common tape measure, the distance between the bottom of the uterus (ie the upper limit of the belly) and the pubic symphysis (ie the lowest point of the belly) If the midwife or doctor notices an abnormality in the measurement, It will be necessary to undergo an ultrasound
The height of the uterine fundus can vary from woman to woman and many factors can influence it. Starting at the 17-18th week of pregnancy, for example, even a full bladder can affect the measurement and therefore it is important to empty the bladder before each measurement.
A smaller-than-expected uterine fundus height could be a sign that the baby is growing slowly or that there is too little amniotic fluid.
Conversely, a higher than expected uterine fundus height could mean that the baby is larger than average, and this may also require more monitoring.
As the uterus grows, it can put pressure on the other organs of the pregnant woman’s body. For example, the uterus may press on the nearby bladder, increasing the need to urinate.
Braxton Hicks contractions
Braxton Hicks contractions, also known as false labor pains, are isolated, non-rhythmic spasms of the uterine musculature that cause a gripping sensation in your abdomen and prepare your uterus for delivery. Irregular and generally painful, they can be felt as early as the 5th month of pregnancy or 6th month of pregnancy and represent a completely physiological phenomenon.
The uterus during labor and delivery
During real labor, the muscles of the uterus contract to help the baby descend into the birth canal (a canal formed by the skeleton of the pelvis and the soft parts that line it).
Labor contractions begin as a wave and increase in intensity, moving from the top of the uterus to the cervix. Your uterus will feel tight during the contraction, but between contractions the pain will loosen and allow you to rest before the next one develops. Unlike Braxton Hicks, labor contractions become stronger, more regular, and more frequent in the run-up to delivery.
The uterus after childbirth
After the baby is born, the uterus will contract again to allow the placenta, which feeds the baby during pregnancy, to be expelled. These contractions are milder than the contractions felt during labor. Once the placenta is delivered, the uterus remains contracted to help prevent bleeding, otherwise known as postpartum hemorrhage.
The uterus will continue to contract even after delivery is complete, during breastfeeding. This contraction and contraction of the uterus will feel a bit like menstrual cramps. These postpartum uterine bites should not worry, as it is a completely normal manifestation which indicates that the new mother’s body is returning to its pre-pregnancy conditions
Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.
She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.