Head Perimeter: Baby’s Head Size Chart in Pregnancy

A subject that has surfaced recently is the importance of measuring the baby’s head in prenatal care , in addition to the common measurement of weight and size . Through an ultrasound , specialized doctors are able to discover any possible problem with the size of the baby’s head just by measuring the head circumference still inside the uterus. In a routine obstetric ultrasound, it is possible to check the size of the baby’s cranial box that is still forming.

In this examination at a certain stage of pregnancy, it is possible to discover some changes still early, only by measuring the head circumference and determining the existence of problems such as microcephaly, macrocephaly, hydrocephalus and some other malformations .

The ideal head circumference for babies at each stage is related to the time of pregnancy. The development takes place slowly and the measures change according to the weeks of gestation that the woman is. However, after birth, it is known that the parameter to be considered “normal” is a head circumference above 33 to 38.6 cm. Below this measure, doctors consider problems such as microcephaly (reduction of the brain) , above that, such as macrocephaly (enlargement of the brain) and even hydrocephalus (water in the cranial box).

Main Causes of Changes

The reasons that cause changes in the head circumference can be diverse, including diseases that the mother contracts during pregnancy. For example , toxoplasmosis, rubella is recently associated with the zica virus . But other factors may also cause these changes in head circumference, as genetic diseases such as Edwards syndrome , Down syndrome , and others.

The increase in head circumference, if proven, there is no cure or treatment . It is important to follow up correctly during pregnancy and talk to the doctor about other tests to be done to determine the reason for the change and the type of problem the baby may have. Some additional tests, such as amniocentesis, can be complementary to the diagnosis, but since it is an invasive method, doctors prescribe it with caution.

There are degrees of change in the cranial box, some babies may have milder degrees of change, such as normality of 33 cm and reduction to 31 cm for example. Children with altered head circumference from greater to greater or lesser may have limitations for the rest of their lives. For example, microcephaly that would cause problems such as intellectual, physical and motor limitations. In addition, they are children who must have special and constant monitoring of different types of treatments such as speech therapists, physiotherapists, neurologists and other professionals.

Head Perimeter Reference Table

We must remember that the table is only a parameter and the measures contained therein do not mean that your baby has a problem. The measures must be evaluated by a doctor for a conclusive diagnosis. If in doubt, contact your obstetrician.

Pregnancy Weeks Minimum Size Average size Maximum size
12 weeks 4,2 6,8 8,8
13 weeks 5,6 8,2 10,2
14 weeks 7,1 9,7 11,7
15 weeks 8,4 11,0 13,0
16 weeks 9,8 12,4 14,4
17 weeks 11,2 13,8 15,8
18 weeks 12,5 15,1 17,1
19 weeks 13,8 16,4 17,1
20 weeks 15,7 17,7 19,7
21 weeks 16,3 18,9 20,9
22 weeks 17,5 20,1 22,1
23 weeks 18,7 21,3 23,3
24 weeks 19,8 22,4 24,4
25 weeks 20,9 23,3 25,5
26 weeks 22,0 24,6 26,6
27 weeks 23,0 25,6 27,6
28 weeks 24,0 26,6 28,6
29 weeks 24,9 27,5 29,5
30 weeks 25,8 28,4 30,4
31 weeks 26,4 29,3 31,3
32 weeks 27,5 30,1 32,1
33 weeks 28,2 30,8 32,8
34 weeks 28,9 31,5 33,5
35 weeks 29,6 32,2 34,2
36 weeks 30,2 32,8 34,8
37 weeks 30,7 33,3 35,5
38 weeks 31,2 33,8 35,8
39 weeks 31,6 34,2 36,2
40 weeks 32,0 34,6 36,6

Readers’ doubts

When there is a change in head circumference, what to do?

When there is a change, the obstetrician will inform and request tests for confirmation and, if necessary, indicate complementary tests to analyze the case more accurately. The ideal is not to despair and wait for confirmation of the next reports and the expert’s opinion.

Are you already mom and trying to have another baby? Pay a visit in our virtual store to know the Famivita products. They were developed to enhance couples’ fertility in a healthy way. You can find vitamins for fertility, lubricating gel that mimics fertile mucus and ovulation and pregnancy tests here at the online store.

See also: Reference Table Fetus Size and Weight in Pregnancy

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My name is Dr. Alexis Hart I am 38 years old, I am the mother of 3 beautiful children! Different ages, different phases 16 years, 12 years and 7 years. In love with motherhood since always, I found it difficult to make my dreams come true, and also some more after I was already a mother.

Since I imagined myself as a mother, in my thoughts everything seemed to be much easier and simpler than it really was, I expected to get pregnant as soon as I wished, but it wasn’t that simple. The first pregnancy was smooth, but my daughter’s birth was very troubled. Joana was born in 2002 with a weight of 2930kg and 45cm, from a very peaceful cesarean delivery but she had already been born with congenital pneumonia due to a broken bag not treated with antibiotics even before delivery.

Dr. Alexis Hart

My name is Dr. Alexis Hart I am 38 years old, I am the mother of 3 beautiful children! Different ages, different phases 16 years, 12 years and 7 years. In love with motherhood since always, I found it difficult to make my dreams come true, and also some more after I was already a mother. Since I imagined myself as a mother, in my thoughts everything seemed to be much easier and simpler than it really was, I expected to get pregnant as soon as I wished, but it wasn’t that simple. The first pregnancy was smooth, but my daughter’s birth was very troubled. Joana was born in 2002 with a weight of 2930kg and 45cm, from a very peaceful cesarean delivery but she had already been born with congenital pneumonia due to a broken bag not treated with antibiotics even before delivery.

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