How many weeks of pregnancy does the fetal head turn downward? Why does the fetal head turn downward during normal pregnancy?

We all know that after a woman becomes pregnant, the fetus will continue to grow and develop in the mother's belly, and the fetal position will also change. Some fetuses change position slightly, while some fetuses change position more frequently. So at how many weeks of pregnancy does the fetus turn its head downward? Let's take a closer look!

At what weeks of pregnancy does the fetus turn its head downward?

Generally speaking, the fetal head starts to turn downward after 28 weeks of pregnancy. Some fetuses will turn their heads downward later. Many babies in breech position may turn to head position again at 36-38 weeks. If the fetus is in an abnormal position at 28-30 weeks and there is no umbilical cord around the neck, the mother can correct the fetal position under the guidance of a doctor. If the baby is still in an abnormal position before delivery, experienced doctors may perform external version to correct the fetal position and adopt a delivery method that is best for both the mother and the fetus.

I believe mothers will have such a question. If the fetus is in the head position, then it is upside down in the mother's belly, with the head down and the buttocks up. Wouldn't the fetus feel dizzy in this position? Wouldn't it be more comfortable to choose a "sitting" position?

Mothers don’t need to worry. The fetus is surrounded by amniotic fluid in the belly and is always in a floating state, just like we are swimming in the water. No matter how we turn, there is water all around and moderate water pressure, so the fetus will not feel any discomfort.

Why does the fetal head turn downward during pregnancy?

Natural Selection

Mothers who have given birth will find that the baby’s body proportions are very disproportionate when it is just born, with the head being larger than the body. Only slowly will the ratio of the head to the body begin to become normal. The fetus has always had this "abnormal" body proportion when it is in the mother's womb. It is precisely because of the fetus's special body structure that the head is the most difficult part to deliver during childbirth.

The fetal head descends and is delivered first, which can make the cervix fully dilate and better stimulate the parauterine plexus. At this time, the fetal head plays the role of "leading". As long as the fetal head can be delivered smoothly, these parts of the body will be easier to deliver. Therefore, in order to be able to "quit the lease" smoothly, the fetus will choose to turn its head down in the mother's belly.

Gravity

The fetus's special body structure is that it has a big head and a small body. The fetus's head develops relatively early, and the head bones account for a larger proportion. Therefore, the fetal head is the heaviest part. Therefore, under the influence of gravity, the fetus's head is more likely to face downwards.

Changes in fetal position during pregnancy

The posture of the fetus in the mother's belly changes slowly, and there is no fixed time for the fetus to turn its head down.

Fetal position before 28 weeks

Before the 28th week of pregnancy, the fetal position is only observed but not diagnosed. Why? Because at this time the fetus is not that big, the space for movement in the mother's belly is relatively large, and the amount of amniotic fluid is relatively large, so the fetal position is changeable. The fetus, this "swimmer", will swim around in the mother's belly, constantly changing its position, sometimes head down, sometimes head up, and sometimes sideways. Therefore, at this time, you only need to observe and no special treatment is needed.

Fetal position after 28 weeks

Active intervention is needed after the 28th week of pregnancy. Under normal circumstances during pregnancy, mothers usually need to undergo 5-6 B-ultrasound examinations, one of which is performed at 28-30 weeks. The B-ultrasound examination at this time is to observe the fetal position. Before 30 weeks of pregnancy, an abnormal fetal position may turn into a head position. If the fetal position is still not correct after 30 weeks, it must be corrected in time, because 30-32 weeks is the best period for correcting the fetal position. At this time, the fetus has not yet achieved the effect of "filling the uterus", and the amniotic fluid has not begun to decrease. The possibility of correction is still relatively large. Therefore, if an abnormal fetal position is found at 28-30 weeks, a diagnosis must be made and corrected in time.

Fetal position after 34 weeks

After the 34th week of pregnancy, the fetus has grown a lot and is almost filling the mother's uterus. The space for movement has therefore been reduced a lot, and the fetal position has become relatively fixed. If the fetal position is still abnormal at this time, the possibility of correction is very low.

Although head down is a normal fetal position and the fetal head will start to turn down at a certain gestational age, some fetuses are affected by various reasons and the fetal position is always abnormal, such as ① the fetal activity space is too large or too small, which may cause malposition; ② the abdominal wall of the multiparous mother is too loose or the uterine malformation such as unicornuate uterus and septate uterus restricts the fetal movement, which may also cause malposition; ③ the umbilical cord is too short, especially when the placenta is attached to the fundus of the uterus, or the placenta is implanted in one uterine horn and placenta previa, which may also cause malposition; ④ too much or too little amniotic fluid, as well as pelvic stenosis, may cause the fetus to have an abnormal fetal position.

Simply put, the fetal head downward rotation means the head is facing downward, which is the normal fetal position. There is no fixed time for the fetal head to turn downward in several weeks.