Fetal Growth Rates at 17 Weeks of Pregnancy - Obstetrics and Gynecology

Dr. Chen Fuhao reply Obstetrics and Gynecology

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A-Feng: Hello! Regarding the questions you raised, they can be divided into two parts: the fetus and the mother.

Fetal Part: The average birth weight of a full-term newborn is approximately 3000 to 3600 grams, depending on factors such as race, socioeconomic status, parental size, and the mother's parity.
Boys typically weigh about 100 grams more than girls.
Clinically, the length of the fetus from crown to heel can be estimated by squaring the number of lunar months of gestation during the first five months; in the second half of pregnancy, this number can be multiplied by 5.
In the latter half of pregnancy, fetal weight increases linearly with time until about the 37th week, after which the rate of increase slows down at varying degrees.

The following chart provides guidelines for estimating fetal age:
| Age (weeks) | Menstrual Age | CR Length (mm) | Foot Length (mm) | Fetal Weight (g) | Major External Features |
|-------------|---------------|----------------|------------------|------------------|-------------------------|
| 11 | 9 | 50 | 7 | 8 | Eyes are closed or have closed; external genitalia indistinguishable.
Intestines within the umbilical cord.
|
| 12 | 10 | 61 | 9 | 14 | Intestines in the abdomen.
Early nail development.
|
| 14 | 12 | 87 | 14 | 45 | Gender can be identified externally.
Neck contour is distinct.
|
| 16 | 14 | 120 | 20 | 110 | Head is upright.
Lower limbs fully developed.
|
| 18 | 16 | 140 | 27 | 200 | Ears protrude from the head.
|
| 20 | 18 | 160 | 33 | 320 | Vernix caseosa appears.
Early toe nail development.
|
| 22 | 20 | 190 | 39 | 460 | Hair on head and body (lanugo) visible.
|
| 24 | 22 | 210 | 45 | 630 | Skin is wrinkled and red.
|
| 26 | 24 | 230 | 50 | 820 | Nails appear.
Body is thin.
|
| 28 | 26 | 250 | 55 | 1000 | Eyes partially open.
Eyelashes appear.
|
| 30 | 28 | 270 | 59 | 1300 | Eyes are open.
Hair growth is good.
Skin slightly wrinkled.
|
| 32 | 30 | 280 | 63 | 1700 | Nails appear.
Body is swollen.
Testes descend.
|
| 34 | 32 | 300 | 68 | 2100 | Nails reach fingertips.
Skin is pink and smooth.
|
| 38 | 36 | 340 | 79 | 2900 | Body is usually plump.
Lanugo almost disappears.
Nails reach fingertips.
|
| 40 | 38 | 360 | 83 | 3400 | Chest is prominent; breasts protrude.
Testes palpable in the inguinal canal.
Nails extend beyond fingertips.
|
CR length and foot length are measured in millimeters, and fetal weight is measured in grams.
These measurements are averages and may not apply to specific cases; variations in measurements increase with age.
The weights refer to fetuses fixed in 10% formalin for about two weeks.
Fresh specimens weigh approximately 5% less.

Source: Williams Obstetrics, Sixteenth Edition.
Additionally, the Maternal Health Handbook published by the National Health Bureau of the Department of Health can provide further reference.
13-16 weeks fetal growth status:
- The baby is fully formed, gender can be distinguished, skin appears translucent with a pink hue, and the baby begins to move.

- The baby measures about 15-18 cm in length and weighs approximately 100-115 grams.
17-20 weeks fetal growth status:
- Fetal movements become more noticeable, the head accounts for about one-third of the total length, bones develop rapidly, and arms and legs are proportionate, with meconium present.
The fetus measures about 25 cm and weighs approximately 225-300 grams.
21-24 weeks fetal growth status:
- The baby's nostrils open, practicing breathing, and the baby can hear sounds.
You can talk to the baby.

- The baby is approximately 30-32 cm tall and weighs about 600-750 grams.
25-28 weeks fetal growth status:
- The skin appears red and wrinkled, subcutaneous fat begins to accumulate, and there are alternating sleep and activity patterns, responding to external sounds.
If born at this time, the baby would be immature and difficult to care for.

- The baby measures about 30-40 cm in length and weighs approximately 1000-1200 grams.
29-32 weeks fetal growth status:
- The skin is less wrinkled, nails grow, eyelids can open, and the baby's activity level increases.

- The baby measures about 42 cm and weighs approximately 1800-2300 grams.
33-36 weeks fetal growth status:
- The rate of weight gain exceeds that of length, lanugo gradually disappears, and the baby's circulatory, respiratory, and digestive systems mature.

- The baby measures about 45-50 cm and weighs approximately 2400-3200 grams.
37-40 weeks fetal growth status:
- The skin is smooth and rounded, the skull is hard, and fingernails and toenails are fully developed.
The fetus measures about 50 cm and weighs approximately 2900-3400 grams.
10-month fetal growth status:
- The baby has grown larger, and the space in the uterus is becoming smaller, resulting in reduced fetal movement.
The baby is positioned head down, with knees close to the nose and thighs against the body.
In contrast to the above, there is a condition known as intrauterine growth restriction (IUGR), which can manifest in two different ways:
1.
Asymmetric growth restriction: Due to inadequate blood flow from the placenta, the fetus cannot reach its growth potential.
This condition is associated with preeclampsia, placental abruption, maternal diseases, and maternal smoking.
The asymmetry arises from a protective effect for the brain, where most blood supply is directed to the brain rather than the liver.
Consequently, the head circumference falls within the same percentile on the growth curve, while the abdominal circumference falls at a lower percentile.
Newborns appear emaciated and are typically long and thin.
2.
Symmetric fetal growth restriction: The fetus grows proportionately but is smaller than expected.
Some infants are born at the lower end of the normal range (e.g., Asian infants), while others may be affected by viral infections or chromosomal abnormalities.
Clinically, the fetus continues to grow smaller than expected (often accompanied by reduced amniotic fluid or abnormal Doppler blood flow).
Maternal Part: Generally, for women with a pre-pregnancy weight within the standard range, the recommended weight gain during pregnancy is as follows:
| Pregnancy Stage | Time Period | Weight Gain (kg) |
|-----------------|-------------------|------------------|
| Early | 1-3 months | 1-2 kg |
| Mid | 4-6 months | 5 kg |
| Late | 7 months to birth | 5-6 kg |
| Total | | 10-15 kg |
Ideal weight gain for pregnant women: If the newborn's weight is 3.2 kg, the placenta weighs about 0.9 kg, amniotic fluid about 1 kg, breast tissue increases by 0.9 kg, blood volume increases by 2 kg, and other body fluids increase by 1.5 kg, the total basic weight gain is 9.5 kg.
Therefore, a weight gain of 10 to 15 kg during pregnancy is considered normal.
Studies indicate that the average weekly weight gain is about 0.3 to 0.5 kg.
The first three months typically see a total gain of 1.5 kg; the fourth and fifth months see a total gain of 2.5 kg; from the sixth month to full term, the gain is about 0.5 kg per week.
Women with a standard pre-pregnancy weight typically gain about 11 to 15 kg.
In summary, I advise you not to worry excessively.
Regular prenatal check-ups and screenings, along with choosing a reliable and trusted obstetrician, will provide dual protection for both mother and fetus.
Congratulations on your future role as a standard good father.
Reference: National Health Bureau of the Department of Health - Maternal Health Handbook, Williams Obstetrics, Sixteenth Edition.

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Reply Date: 2007/05/17