Fetus at 39 weeks of pregnancy: norms and features

The 39th week of pregnancy is a critical period for both you and your unborn child as you near the end of your pregnancy. Your child has nearly completed the development of all the essential organs and systems required for life outside the womb by now, making them nearly ready to face the outside world. As you get ready for childbirth, this time is a mixture of anticipation and preparation.

Your baby is probably between 19 and 21 inches long and weighs between 5.5 and 8 pounds at 39 weeks. Their body is getting plumper, and those soon-to-be chubby cheeks are getting filled out. The baby may begin to move more slowly as the uterus gets more constricted.

As delivery approaches, knowing what’s typical at this point can make you feel more prepared and assured. Let’s talk about what to expect in these last few days and how your baby is preparing for their public debut.

Aspect	Details
Size	At 39 weeks, the fetus is about the size of a watermelon, weighing around 5.5 to 8 pounds (2.5 to 3.6 kg) and measuring 19 to 21 inches (48 to 53 cm) long.
Development	Most major organs are fully developed. The lungs are maturing, and the baby is gaining fat for insulation.
Position	The fetus usually moves into a head-down position in preparation for birth.
Movements	Movements may feel more restricted due to less space, but the baby should still be active.
Skin	The skin is becoming smoother as the baby continues to accumulate fat.
Head	The baby"s head may have a slightly elongated shape to help fit through the birth canal.
Amniotic Fluid	Amniotic fluid levels might decrease as the baby gets ready for birth.

Height and weight

Eight months and three weeks have passed during the woman’s pregnancy. In this time, the infant has grown from a tiny collection of cells into a robust adult, prepared for life beyond the mother’s womb. His weight and height this week are highly unique and based on both genetics and the success of the pregnancy during the preceding months.

Most of the time this week, the baby’s weight has surpassed the psychological threshold of three kilograms.

A large child may weigh up to 4 kilograms, with the expected weight of 2900 grams being the minimum average value at this point.

The likelihood of giving birth to a "hero" increased with the fullness of the pregnant woman’s nutrition and the ease of the gestation period. Hereditary factors also play a significant role; large parents typically give birth to large children, and small-framed, thin parents "get" a baby in the maternity hospital with less remarkable parameters.

The baby is 48–58 centimeters tall at 39 weeks, but even in this range, there are unique genetic "corrections."

The baby will grow a little more and gain a little weight, but not more than 50–100 grams, if labor does not start this week. During the final weeks of pregnancy, the child’s growth rate slows down.

Fetometry norms

As a result of children’s varying sizes, fetametry norms—which are determined by ultrasound measurements—no longer have the same diagnostic value as they once did.

They are more important for estimating the fetus’s weight and organizing the delivery strategy.

The primary dimensions’ average norm is as follows:

• biparietal size of the head (BPD) — 94-95 mm (a value from 86 to 102 mm is also considered normal);
• fronto-occipital size of the head (FOH) — 119 mm (from 108 to 129 mm is also acceptable);
• length of the femur (FL) — 73-74 mm (fluctuations from 68 to 79 mm are possible);
• length of the shin bones (LKB) — 65-66 mm (normally it can be from 61 to 71 mm);
• length of the humerus (LHU) — 64-65 mm (also acceptable from 60 to 70 mm);
• length of the forearm bones (LFB) — 56-57 mm (normally the size can fluctuate from 51 to 60 mm);
• abdominal circumference (OC) — 336-342 mm.

With most of its organs fully formed and functioning, the fetus is deemed full-term and ready for delivery at 39 weeks of pregnancy. Usually, the baby is between 19 and 21 inches long and weighs between 7 and 8 pounds. Though the baby’s movements may seem less frequent as their space becomes more limited, their vital systems, such as their brain and lungs, are still developing and fine-tuning. Numerous indicators, like decreased abdominal pressure and erratic contractions, suggest that labor might begin at any time.

Appearance

The baby at 39 weeks has a unique charm because of the subcutaneous fat layer that the unborn child "built up" during the third trimester of pregnancy. The baby’s skin has smoothed out all wrinkles and folds, giving it a normal pink color. This is because the capillaries and vascular network that gave the child’s skin a reddish-purple tint have disappeared.

The baby’s body was covered in fluffy hair, but that has vanished. The skin is now soft and smooth. The white lubricant that was initially applied to the baby’s body has vanished as well. Though the fetus is located in an aquatic environment, mechanical rubbing is not excluded in the groin area, neck, and folds on the arms and legs where only a small amount is left where it is now needed.

The infant may have a full head of hair, or he may be completely hairless except for a few light-colored, sparse hairs. This is also a personal characteristic.

The genitalia are developed fully. The testicles have already lowered into the scrotum in nine out of ten boys, and in girls, the labia majora cover the labia minora. Babies’ external genitalia and nipples may appear somewhat swollen as a result of the mother’s sex hormones. However, this is a transient phenomenon; during the first few months following delivery, everything will return to normal.

Development of organs and systems

The baby is regarded as fully mature at this point. The baby is fully prepared for life beyond the mother’s womb if the birth takes place in the next few days. His heart rate (HR) is roughly 157 beats per minute; it beats continuously and smoothly.

Boys’ hearts beat a little bit more slowly than girls’. After taking its first breath, the baby’s lungs are prepared to open. They have gathered enough of a substance called surfactant to allow for independent breathing since the lungs will no longer adhere to one another.

The interaction between the digestive organs has already been fully "rehearsed" by them. The amniotic fluid that has entered the stomach can be broken down by it. The mother experiences consistent, rhythmic jolts in one area of her abdomen when her baby burps up any excess food that was swallowed. The infant hiccups a lot.

Nutrient absorption occurs through the sensitive villi found on the inside walls of the intestine. Meconium, the original green feces that the baby uses to go "big" in the toilet for the first time on the first day after birth, has already accumulated in the intestines.

The urethra, ureters, bladder, and kidneys are all operating at maximum efficiency. The body of a baby is formed and functional, with the liver, spleen, pancreas, and gall bladder producing their own hormones and enzymes.

The developing stage of the fetus’s nervous system continues. And after birth, this will still happen. New connections between neurons form on a daily basis, and the brain "learns" to coordinate every bodily function.

However, the infant has already made enormous progress; it can already perform more than 70 reflex automatic movements that are necessary for survival.

The reflexes for breathing, swallowing, sucking, and grasping are the strongest.

What the baby feels?

The baby has highly developed senses. He has excellent hearing, as long as he can hear the amniotic fluid, the mother’s thick abdominal wall, and the sounds inside, such as her heartbeat, the roar of blood in her arteries, and the "rumbling" of her intestines. However, the baby is still able to recognize his mother’s voice and other familiar sounds even with this kind of sound accompaniment.

When the door slams or the alarm clock suddenly rings, many mothers observe that an active baby either becomes quiet or, on the other hand, begins to "rage."

The infant’s eyes are still "tuning in." He can now tell the difference between light and dark, and the world inside the uterus seems to be made up of a collection of unevenly sized and colored spots. Soon after birth, he will learn to focus his gaze and subsequently identify colors. Although the baby is still unable to detect smells, their developed tongue and inner cheek taste buds allow them to accurately perceive flavors.

Movement

In the womb, the baby experiences discomfort and cramping. Since it occupies all of the available space, it is uncommon to see active fetal movements at 39 weeks. At this point, the majority of pregnant women report that the baby has quieted down and is not moving much. The infant, however, continues to follow a unique schedule in which rest intervals are interspersed with periods of activity.

While some babies sleep with their mothers at night and move a lot during the night, others only move during the day. Pregnant women frequently report that babies who are older actively move in the morning and evening. In a 12-hour period, there should be a minimum of 10 motor episodes regardless of the activity regimen.

In light of the apparent decline in activity, the expectant mother may start to experience uncomfortable and painful sensations from her movements this week.

They are connected to the fetus’s size and to the amniotic fluid level decreasing, which is normal at this point.

Presentation

Babies typically adopt the starting-athlete stance at 39 weeks gestation. This week, it is pressed against the small pelvic exit, where most babies are head down. In order to get through the birth canal more easily, the fetus presses its chin firmly against its chest.

There is nearly no possibility that the baby will turn over and move around properly during childbirth if it is not positioned cephalically in the uterus at 39 weeks.

A planned cesarean section is indicated in cases of breech presentation, where the baby is positioned with its bottom facing the small pelvis, or transverse presentation, which is relatively uncommon and involves the baby lying across. This week or the next, it is performed.

Possible problems

This week is a typical week for childbirth, with 40% of women giving birth at 39 weeks. Their unusual onset, such as amniotic fluid leakage, may be an issue.

Unscheduled medical attention should be sought if you experience a discharge of watery liquids. He’ll be able to assess the baby’s condition and determine whether any water is leaking and how much is left.

An unscheduled CTG will be conducted to assess the baby’s condition and to measure the amniotic fluid index, which indicates how much fluid is in the amniotic sac.

The mother will be shown an urgent delivery if the results of the cardiotocography reveal anomalies in the condition of the fetus, such as tachycardia or bradycardia in the infant.

The woman will remain in the hospital for 24-hour observation if the baby feels well and the water intake is still adequate, as this will allow her labor to start as soon as possible.

At 39 weeks, the placenta may exhibit pathological alterations such as becoming excessively thin, aging too quickly, or ceasing to supply the baby with oxygen and nutrients. In this instance, starting labor or doing a cesarean section also signals delivery.

Your baby is almost ready to meet the outside world at 39 weeks. With the brain still growing quickly and the lungs fully developed, most development is finished. Because there is less room in the womb, the baby may move less, but occasional rolls and kicks are still normal.

It’s critical to keep an eye out for labor symptoms and maintain regular communication with your healthcare provider as delivery draws near. Since every pregnancy is different, follow your gut and get help if something doesn’t feel right.

Though it may be an exhilarating and anxious moment, keep in mind that your body is built for this procedure. Remain upbeat, look after yourself, and prepare for the birth of your child.

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