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.
Provided below is an index with the 8 points we are going to expand on in this article.
Changes in the fetus
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.
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.
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.
- Hematopoiesisbegins. It 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.
- 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.
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.
- You may begin to notice certain movements of the baby, but usually a few weeks later (around the 18th week of gestation).
- 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.
- Increased appetite, as the baby is more developed and requires more energy.
- Appearance of cavities and bleeding gums due to vitamin deficiency.
- Back pain due to the volume of the abdomen.
- Increased salivation in relation to elevated estrogen levels. This is known as hypersialorrhea o ptyalism.
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.
- 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 generally this ultrasound isn´t performed until the 20th week of pregnancy.
- Screening 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. This screening is also recommended at 12 weeks of gestation.
- 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.
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.
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.
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?
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Cabanyes, J. El comportamiento fetal: una ventana al neurodesarrollo y al diagnóstico temprano. Septiembre 2014. Pediatría Atención Primaria vol.16 (63). DOI: 10.4321/S1139-76322014000400012
Health Service Excecutive (Feidhmeannacht na Seirbhíse Sláinte) (2010). A guide to your pregnancy month by month. Breastfeeding.ie - Your breastfeeding support network. Order Code: HPM00341
Zheng, Y, Zhang, C, Weisskopf, M, Williams, PL, Parsons, PJ, Palmer, CD, Buck Louis, GM, James-Todd T. A prospective study of early pregnancy essential metal(loid)s and glucose levels late in the second trimester. J Clin Endocrinol Metab. 2019 May 16. DOI: 10.1210/jc.2019-00109
FAQs from users: 'At what age is amniocentesis recommended?', 'At 16 weeks of pregnancy, can the sex of the baby be seen by ultrasound?', 'What month is the 16th week of pregnancy?' and 'In the case of twin pregnancy, are the changes that occur at 16 weeks similar?'.
Authors and contributors
More information about Cristina Algarra Goosman
Hi, I am in week 14 but they tell me my baby is measuring about 16 weeks, is that bad?
The measurement of the fetus is done on the basis of scales, i.e., measurements are taken and compared by gestational age.
If your baby is measuring more than it should for a week of pregnancy, it can mean several things, the weeks of pregnancy are counted based on the first day of the last menstrual period, or the date of conception (or ovulation). Not all women have regular cycles or cycles that are 28 days long with ovulation around day 14 (how the average is considered and on which the scales are created).
It can also be justified by the percentiles of the scale, i.e. the measurement is compared with other babies of the same gestational age and divided into community percentiles.
If your baby is healthy and the doctor considers it appropriate, it may simply be that your baby is slightly larger than average.
I hope I have helped you,
Hello, this is my first pregnancy and I am at the end of week 16 since one or two days ago I am noticing bubbles in my belly, is it possible that the baby is moving? I notice it, especially at night
The strange sensations in the lower belly may be the movements of your baby. Around 16 to 20 weeks is when you may start noticing these movements.
There are different characteristics that advance or delay these sensations, such as the mother’s weight, whether she is a first-time mother or has had other pregnancies, and her lifestyle.
As a general rule, in utero babies are rocked during the day by the mother’s movements. When night falls and the mother sleeps, she has no external stimulus and therefore wakes up and moves.
I hope I have solved your question