What is the bimaxillary diameter at 20 weeks for a boy?

What is the biparietal diameter of the fetus at 20 weeks to determine if it is a boy? The biparietal diameter of the fetus is mainly used during pregnancy to check whether the baby's development is healthy. Under normal circumstances, the biparietal diameter of the fetus cannot be used to determine the gender of the fetus. The gender of the fetus can be determined through amniocentesis, B-ultrasound, etc. Let's learn about it together.

1. How long does it take for the fetus's bimaxillary diameter to be a boy?

In fact, it is unreasonable to use the fetal bimax diameter to determine the gender of the fetus, but there is a folk saying that the fetal bimax diameter can determine the gender of the fetus.

First of all, if the parents are tall and strong, then regardless of whether they are pregnant with a boy or a girl, the double-bone ratio will basically exceed 2.1 in the late pregnancy (after 30 weeks). If it is not ruled out that it exceeds 2 in the early stage, it is not easy for such parents to use this method to distinguish the gender of the baby.

On the contrary, if the father and mother are not tall, then the baby is not big. At the beginning of the 24th week of pregnancy, the fetal biparietal diameter minus the fetal femoral length = 1.7 or more. From then on, the fetal biparietal diameter-fetal femoral length will gradually increase in each B-ultrasound. If the difference is 1.7 at 24 weeks, 2 at 28 weeks, and 2.1 at 30 weeks, then the baby created by this type of mother is likely to be a boy, and the probability of having a boy increases by 80%.

2. Other ways to determine the gender of the fetus by measuring the bimaxillary diameter

In fact, using the fetal bimax diameter to determine whether the baby is a boy or a girl is not scientifically researched and has no basis.

At present, the methods that obstetricians and gynecologists can use to determine the sex of the fetus are:

1. Ultrasound scanner: Ultrasound is a type of sound wave frequency. So far, reports have shown that it has no adverse effects on the fetus, so it is widely used in obstetrics and gynecology. When using ultrasound to confirm the sex of the fetus, the accuracy of male babies is more than 95%, while the reliability of female babies is only about 85%.

2. Amniocentesis: Amniocentesis is mainly used to confirm whether the fetus has defects in sex chromosomes or neural tube defects. It is usually performed between 16 and 20 weeks of pregnancy. Because the sex chromosomes of the fetus can be known, the sex of the fetus can also be known. The accuracy is 99%, but there is a 1% chance of miscarriage. Therefore, doctors do not agree to perform amniocentesis only for the purpose of determining the sex of the fetus.

3. Villus sampling: Also known as "villus sampling", it is usually done at 8 to 10 weeks of pregnancy. The main purpose is the same as amniocentesis, which is to confirm whether the sex chromosomes of the fetus are normal, but many people also use it to confirm the sex of the fetus, with an accuracy of 98%.