Week 16 of pregnancy: changes in the fetus and mother

The 16th week of pregnancy is the last week of the fourth month of gestation and many changes occur in the baby.

The uterus has already reached a considerable size and the blood vessels are compressed, so the woman may experience swollen feet, tired legs, varicose veins, etc. For these reasons, week 16 of gestation is a good time for the mother-to-be to start practicing moderate sports.

However, the mother should be happy and calm because if she has not yet felt the baby, she will soon feel it moving inside her.

The different sections of this article have been assembled into the following table of contents.

Changes in the fetus

A 16-week-old baby measures approximately 11-13 cm and can weigh 80-100 g. In addition, it has a head diameter (BPD) of 33 mm and a femur length of 21 mm.

Fetus in the 16th week of pregnancy

From the 16th week of pregnancy, the baby begins to develop the bones of the ear and the back muscles are gaining volume and strength. Therefore, it will be able to respond to stimuli and recognize sounds. In addition, the brain acquires the function of limb control by increasing sensory capacity.

In general, the baby begins to have more balanced proportions, the eyes appear centrally located and the ears ascend to occupy their almost definitive position.

In relation to the changes that occur in the baby during the 16th week of pregnancy, the following can be highlighted:

• Hair appears on the eyebrows and on the upper lip. This hair falls out after birth.
• Nails form on the fingers and toes.
• Development of epidermal folds on the palms of the hands and fingers. In addition, the baby already has a fingerprint.
• The legs are longer than the arms and with great mobility.
• Knees, ankles, elbows, wrists, and fingers can be differentiated. This development allows the baby to be more functional and to be able to open and close his hands, move his legs, etc.
• The eyelids are closed but begin to make small movements of the eyes from side to side.
• The pressure reflex develops so that the baby is able to grasp the feet or the umbilical cord. It also allows you to keep your fists closed.

Main fetal changes at 16 weeks of gestation

In addition, this week of pregnancy marks the beginning of hematopoiesis. This is the process of formation, development and maturation of the elements that make up the blood (red blood cells, leukocytes, platelets, etc.). Thus, the baby will have its own blood and its heart will be in charge of pumping it.

Symptoms and changes in the mother

The 16th week of gestation, along with the rest of the weeks that make up the fourth month of pregnancy, is one of the best times for the mother because she has already become accustomed to all the hormonal change. Despite this, the expectant mother will continue to experience changes and will notice some of the symptoms listed below.

• The size of the uterus increases. The uterine height from the fundus to the pubis measures 14 cm. The mother may feel the lower part of the abdomen hard and there may be pinching or discomfort in the sides of the uterus. This is not a cause for concern, as it is the adaptation of the ligaments to the new uterine shape.
• Disappearance of morning sickness and vomiting.
• Night cramps due to involuntary contractions of the baby.
• Constipation due to the combination of pregnancy hormones and the pressure of the uterus on the intestines.
• Increased breast volume and sensitivity.
• Back pain due to the volume of the abdomen.
• Increased salivation in relation to elevated estrogen levels. This is known as hypersialorrhea o ptyalism.

Maternal symptoms in the 16th week of pregnancy

In addition, the mother will feel greater appetite, since the baby is more developed and requires a greater energy intake. During this week of pregnancy, cavities and bleeding gums may also appear due to a lack of vitamins.

Occasionally, the pregnant woman may begin to notice certain movements of the baby in the 16th week of pregnancy. However, the most common is a few weeks later, around the 18th week of gestation.

Pregnancy control: diagnostic tests

When a woman becomes aware that she is pregnant, it is important to keep control of her pregnancy to avoid risks.

Between the 16th and 20th week of gestation, a few years ago doctors used to determine alpha-fetoprotein (AFP). Increased AFP indicates possible neural tube defects (spina bifida); whereas decreased levels of this protein are indicative of Down syndrome.

However, at present this test is not recommended by the Spanish Society of Obstetrics and Gynecology (SEGO) because it provides numerous false positives, that is, it reports some defects that are not real.

Therefore, the most recommended tests for the 16th week of pregnancy are:

• Routine blood pressure control, blood tests, weight control, etc.
• Amniocentesis This is an invasive prenatal test that involves the extraction of amniotic fluid by puncturing the mother's abdominal wall. The extracted amniotic fluid will be analyzed and the baby's karyotype, that is, its set of chromosomes, will be obtained. In this way, chromosomal alterations can be detected.

Medical tests in the 16th week of pregnancy

Additionally, there are women who go privately to have an ultrasound to find out the sex of the baby in the 16th week of pregnancy, since the Social Security does not perform this ultrasound until a few weeks later.

In the case of women who have not had it done in the 12th week of pregnancy, it would also be advisable to screen for asymptomatic bacteriuria. During pregnancy there is an alteration in the ability to empty the bladder and the properties of urine are modified, so it is more common for microorganisms to grow and cause infections.

Recommendations at the end of the fourth month of pregnancy

In the 16th week of pregnancy, it is recommended to do some type of moderate physical exercise or sport. This stimulates blood circulation and reduces lumbar discomfort. The sport most recommended by doctors during pregnancy is swimming.

In addition, abundant water consumption will promote hydration and blood circulation. Feeding must be adequate to ensure the correct supply of nutrients to the baby. With a healthy, varied, and balanced diet, the mother will feel better and will favor fetal development.

Care in the 16th week of pregnancy

In any case, all the instructions given by the obstetrician will be followed at all times to avoid risks that may occur during pregnancy.

FAQs from users

At what age is amniocentesis recommended?

Amniocentesis is an invasive prenatal technique that is recommended from the age of 35; while from the age of 40 it becomes a mandatory test.

This technique will also be recommended in women who have had a history of repeated miscarriages or other previous pregnancies with chromosomal alterations, regardless of age.

At 16 weeks of pregnancy, can the sex of the baby be seen by ultrasound?

From 12 weeks the sign of the genital tubercle can be seen. From the 16th week onwards, the male and female genitalia can be visualized as long as the fetus is well-positioned.

What month is the 16th week of pregnancy?

The 16th week of gestation corresponds to the last week of the fourth month of pregnancy. This week is therefore included in the second trimester of pregnancy.

In the case of twin pregnancy, are the changes that occur at 16 weeks similar?

Yes, the mother and fetuses will experience the same changes as with a singleton pregnancy. With a twin pregnancy it is possible that in the 16th week you may notice more marked movements of the babies.

Recommended readings

If you want to know how the pregnancy is going to evolve, we invite you to read the article of the next week of gestation: 17th week of pregnancy.

We have also talked about amniocentesis, so if you want to learn more about this technique we recommend you to visit the following link: Amniocentesis: what are its indications and possible risks?

References