What happens inside the womb during birth?

Answer 1

Prior to labor, hormones shift so pregnancy hormones start to drop. Oxytocin begins to act on the uterus. A woman can have false labor, Braxton-Hicks contractions, within two weeks of delivery. The baby has, by then, usually "dropped" so its head is closer to the pelvis. The woman can suddenly breathe easier because the baby is no longer pressing against the diaphragm. But because the head presses on the urinary bladder, the woman often feels she needs to urinate more often.

As oxytocin increases, contractions become more regular. Doctors advise first-time moms go to the hospital when contractions are evenly 2 minutes apart. However, most moms find out that with all the excitement, distractions, and moving around, suddenly contractions seem to stop. But it's just fooling the mom. The contractions do resume. The top of the uterus, called the fundus, is contracting hard, forcing the baby downward with each contraction. The head will "engage," meaning it has entered between the pelvic bones, pressing more against the cervix. This pressure, along with the natural hormones, begins to thin and expand the cervix. This is called dilation of the cervix. The cervix needs to be 10 cm for the baby's head and shoulders to push then slip through the cervix into the vagina. But--there's a lot happening before then!

Most of what happens in the uterus seems repetitive--because it is repetitive, made up of contractions with periods of relaxation of the uterine muscle. In NORMAL labor, the hormone's effects plus the contractions stops smaller blood vessels from bleeding during labor. The placenta is still attached AND functioning-- the baby needs the oxygen from the mother through the placenta. If the placenta detaches during labor, the woman could hemorrhage AND this could cause fatal injury to the baby. The placenta during labor only becomes a problem if the egg attached LOW in the uterus, versus up high where it should be.

So labor progresses, each contraction forcing the baby downward. By the time the cervix is 8 cm open, the cervix has completely thinned and widened-- there is an opening for the baby. The baby's head can be right above or "in" the cervical opening during each contraction. (This is often when a doctor inserts a monitor into the baby's scalp.)

The mom feels increasing desire to PUSH. The nurse or doctor will tell the mom when it is time to keep panting, or time to push. As the mom pushes, the head fully pushes through the cervix. The top of the uterus begins to lose its large pregnancy expansion, but the uterus is still large. Each push makes the baby come further into the vagina. In a normal, uneventful birth, the head delivers first. Then one shoulder, then the other shoulder. The woman feels fewer uterine contractions; the focus has shifted lower. She may feel she has to defecate (have a bowel movement; that's why a nurse gave an enema right after the mom got to the hospital). Once both the head and both shoulders delivers, the pain and pressure eases a lot. The back, bottom, and legs of the baby slip out with just one more push.

The doctor cuts and clamps the umbilical cord and the baby is assessed, then given to the mom. But nature is still doing its work in the uterus. Contractions (and hormones in the blood) now work to detach the placenta from the uterine wall so the placenta can also be "delivered." Blood vessels in the uterus do bleed, but more like a very heavy period. If the placenta detaches normally, the contractions may be enough to push it out. If not, the nurse presses and massages the uterus starting from the fundus--the top--downward.

(If there is a medical problem, one nurse takes the baby to the nursery, so staff can focus only on the mom.) IF the placenta is retained, or if it ripped but won't fully detach from the uterine wall, the woman can hemorrhage, and quickly! She can bleed to death. If the woman is hemorrhaging, the nurse's continued pressure on the uterus will keep the uterus from filling with blood AND this pressure from outside will press against the bleeding blood vessels in the uterus. Just like a cut on your finger, putting pressure on bleeding will slow the bleeding and allow the wound to clot. But the uterus has many tiny blood vessels, so the pressure needed is more intense. The doctor or doctors will manually remove the placenta (yes, only immediately after delivery can a full forearm and hand fit through the vagina and cervix to reach and tug on a low-positioned placenta). Once the placenta is removed, the woman may need a blood transfusion if the blood loss was great. The uterus may need other medical interventions, like packing inside the whole uterus with gauze, to keep blood vessels from continuing to heavily bleed and the gauze being packed in tightly exerts pressure on the blood vessels.

After delivery, the woman's body is doing two things: continuing to exert hormonal influences on the mammary glands in the breasts to produce breast milk within a few days to a week. But hormones associated with pregnancy continue to fall, and the body begins to reset to prepare for a woman's normal menstrual cycle. Post-delivery bleeding can continue for many days; then, the cycle of influences from non-pregnancy menstrual hormones begins all over again.