Second trimester of pregnancy: growth and well-being

The second trimester spans approximately 13 to 27 weeks of pregnancy—a period when most women experience a reduction in early morning sickness and an increase in energy levels. Many clinical guidelines recommend that routine fetal anatomical ultrasound examinations and a range of laboratory screening tests be performed during this trimester. [1]

Physiologically, this is a time of rapid fetal growth and active organ development. The fetus develops the basic structures of the central nervous system, heart, kidneys, and limbs; the volume of amniotic fluid increases, and the placenta continues to grow and improve uteroplacental blood flow. These processes determine the choice of examinations and attention to the mother's symptoms. [2]

For the mother, the second trimester is typically characterized by steady weight gain, increased blood volume, and possible cardiovascular changes: increased cardiac output and displacement of the diaphragm as the uterus grows. These physiological changes impact well-being and objective indicators in anthropometry and laboratory tests. [3]

Scheduling doctor visits during this period is aimed at early detection of pregnancy complications, assessing fetal growth, and preparing the mother for further monitoring. Many national guidelines recommend at least two follow-up appointments in the second trimester, including mandatory anatomical ultrasound examination. [4]

Recommended visits and screenings

Routine examinations in the second trimester include an anatomical ultrasound at 18+0 to 20+6 weeks, screening for gestational diabetes at 24–28 weeks, and laboratory tests as indicated. Ultrasound is used to assess fetal anatomy, placental position, and amniotic fluid volume. [5]

In some cases, screening for gestational diabetes is performed earlier in the presence of risk factors: excess body weight, previous gestational diabetes or type 2 diabetes in the medical history, multiple pregnancies, maternal age ≥35 years. Treatment results and early diagnosis influence perinatal outcomes, so these tests are clinically significant. [6]

In addition to the above screenings, tests for anemia are performed in the second trimester, and if necessary, blood group and Rh factor determination are performed, as well as testing for infections as part of screening programs (e.g., serology for syphilis, HIV, and hepatitis B where recommended). Individual tactics depend on local protocols and the status of previous studies. [7]

The arrangement of contacts and frequency of visits may vary: WHO recommends a model of at least eight contacts during pregnancy with scheduled visits at 20 and 26 weeks; in practical routine care, the frequency of visits is often determined individually by the treating physician. [8]

Table 1 - Main examinations and their timing

Examination	Estimated timeframes	Target
Anatomical ultrasound	18+0 - 20+6 weeks	Assessment of fetal anatomy, position of the placenta
Screening for gestational diabetes	24 - 28 weeks	Detection of carbohydrate metabolism disorders
Anemia test	14 - 28 weeks (as indicated)	Hemoglobin assessment, need for iron therapy
Determination of blood type and Rh factor	1st or 2nd trimester	Identification of potential Rh incompatibility
Screening for infections (according to local recommendations)	1st or 2nd trimester	HIV, syphilis, hepatitis B, etc.

Fetal development and gestational age expectations

By 20 weeks, the fetus has clearly formed organs and is measured by femur length, head circumference, and abdominal circumference; assessment of the structure of the heart, kidneys, and brain is part of the standard anatomical scan. Normal size and the absence of major anatomical defects serve as an important guide for the rest of the pregnancy. [9]

Fetal growth accelerates: by the middle of the second trimester, a subcutaneous fat layer and pronounced motor activity, which the mother begins to notice as fetal movements, have already formed. The frequency of fetal movements and the dynamics of fetal weight gain are used to monitor well-being. [10]

The placenta continues to develop and provides gas exchange and nutrition to the fetus; if a low-lying placenta is detected on ultrasound, subsequent monitoring is required for placental displacement as the uterus grows. Placental abnormalities may manifest as bleeding or impaired fetal growth and require specialized management. [11]

Evaluation of the volume of amniotic fluid is part of the standard examination; excessive or decreased amounts of amniotic fluid require further diagnostics to identify the causes and plan the tactics. [12]

Table 2 - Average fetal growth guidelines by week

Duration, weeks	Coccygeal-parietal size, mm	Fruit weight, g (approx.)
14	80	43
16	125	100
20	160	300
24	210	600
28	230	1000

Nutrition, weight gain and vitamins

Recommended weight gain varies depending on the mother's initial body mass index. For a woman with a normal body mass index, a total weight gain of approximately 11-16 kg is recommended throughout pregnancy; weight distribution in the second trimester typically results in a steady monthly increase. Individual weight gain goals are determined by a prenatal care professional. [13]

Energy and micronutrient needs increase; key recommendations include adequate protein intake, iodine and iron intake, and maintaining folate levels before and during pregnancy. Iron deficiency anemia is diagnosed by laboratory testing and, if necessary, requires correction with iron supplements under medical supervision. [14]

Vitamin D and calcium are important for fetal bone mineralization and maternal bone metabolism; deficiencies are corrected according to local guidelines. Multivitamin supplementation is considered as a supplement for deficiencies or increased needs, but routine overdosing is not recommended. [15]

Gestational diabetes mellitus affects dietary recommendations: if abnormalities are confirmed, individualized dietary therapy with glycemic monitoring and, if necessary, pharmacotherapy are administered. Early diagnosis and monitoring reduce the risk of complications during childbirth and future metabolic disorders in mother and child. [16]

Table 3

Initial body mass index	Recommended weight gain, kg
Less than 18.5	12.5 - 18
18.5 - 24.9	11 - 16
25 - 29.9	7 - 11.5
30 or more	5 - 9

Physical activity and work demands

Moderate physical activity such as walking, swimming, stretching, and low-intensity strength training is generally safe and beneficial during the second trimester, unless contraindicated. Regular activity improves well-being, reduces the risk of excessive weight gain, and helps prepare for childbirth. Consult a doctor before beginning any new exercise routine. [17]

Work involving heavy physical labor, prolonged standing, or exposure to harmful factors should be assessed individually. If pregnancy complications arise, a physician may recommend temporary workload restrictions or a change in work schedule. Occupational safety conditions for pregnant women are regulated by local laws and clinical guidelines. [18]

Rest and daily routine are important: sleeping on the left side can improve venous outflow and reduce compression of the inferior vena cava in a recumbent woman; however, in daily life, positions alternate and should be comfortable. Prolonged exposure to hot environments and excessive overheating should be avoided. [19]

When planning trips and flights, it is worth considering the gestational age and individual risks: many sources say that flights are safe up to 36 weeks in the absence of complications, but you should discuss the details with your doctor before traveling. [20]

Table 4 - Physical activity recommendations

Type of activity	Recommendations
Walking	30 minutes daily or a total of 150 minutes per week
Swimming	2-3 times a week is safe in the absence of complications
Strength exercises	Low load, under instructor supervision if necessary
Avoid	High-impact and contact sports

Common complaints and how to deal with them

Low back pain and uterine ligament strain are common symptoms in the second trimester. Therapeutic exercise, correct posture, orthopedic support, and, if necessary, a consultation with a physiotherapist are recommended. The use of painkillers requires consultation with a specialist. [21]

Heartburn and constipation are associated with hormonal changes and pressure from the uterus on the gastrointestinal tract. Prevention and treatment include dietary measures: frequent meals, increased fiber intake, and adequate fluid intake; if necessary, safe medications are prescribed as recommended by a doctor. [22]

Moderate leg swelling is common and usually physiological; if severe unilateral swelling, rapid weight gain, or associated symptoms occur, consult a doctor to rule out preeclampsia and thrombosis. Blood pressure monitoring and periodic assessment of urine protein are important. [23]

Psycho-emotional changes, anxiety, and mood swings require attention: talking with an obstetrician-gynecologist, a clinical psychologist, or participating in support groups can help reduce stress and prepare for childbirth. Ignoring severe anxiety can worsen outcomes for both mother and child. [24]

Table 5 - Common symptoms and rational measures

Symptom	What helps?	When to see a doctor
Back pain	Exercises, orthopedic belt, physiotherapy	Increased pain, neurological symptoms
Heartburn	Eat small meals frequently, avoid fatty and spicy foods	Sudden weight loss, severe vomiting
Constipation	Fiber, water, physical activity	Blood in the stool, prolonged obstruction
Edema	Leg raises, compression stockings	Unilateral severe swelling, pain in the shin

Warning Signs: When to Seek Immediate Help

Spotting or heavy vaginal bleeding at any point during pregnancy requires urgent evaluation. Bleeding may be a sign of a threatened miscarriage, placental abruption, or placenta previa; early diagnosis impacts available care options. [25]

Severe and persistent headache, blurred vision, significantly elevated blood pressure, severe abdominal pain, and nausea beyond normal limits are possible signs of preeclampsia or other serious conditions. If these symptoms occur, seek immediate medical attention. [26]

A sudden and dramatic decrease in fetal movements after a period of activity warrants an urgent assessment of fetal condition. Monitoring fetal movements remains a simple and informative method for self-monitoring fetal well-being outside of hospitalization. [27]

High fever, severe infectious symptoms, difficulty breathing, and signs of thromboembolism all require urgent medical evaluation and treatment. Early diagnosis and treatment reduce the risk of adverse outcomes. [28]

Vaccinations, medications, and drug safety

Many national recommendations recommend influenza vaccination during pregnancy and pertussis vaccination in the mother during the third trimester as important measures to protect the newborn and mother. Decisions on specific vaccines and timing are based on local recommendations and the mother's condition. [29]

Regarding medication use in the second trimester: any medication should be based on a benefit-risk assessment; many medications are safe, but there are some that are contraindicated during pregnancy. It is important to have a list of all medications you are taking and discuss them with your doctor. [30]

Antibacterial therapy for infections is selected taking into account the safety of the fetus; many antibiotics have approved indications, but some are contraindicated. If an infection is present, prompt diagnosis and adequate treatment are essential. [31]

The use of over-the-counter medications and herbal remedies should be discussed with a doctor, as "natural" does not mean "safe" for the fetus and mother. Pregnancy management should consider possible drug interactions and long-term effects. [32]

Preparing for the third trimester and childbirth

The second trimester is a convenient time to plan for the next steps: choosing a maternity facility, discussing birthing options, completing necessary paperwork, and preparing for breastfeeding. Informed decision-making and preparation reduce anxiety before childbirth. [33]

It is recommended to continue monitoring by an obstetrician-gynecologist or midwife, complete prescribed examinations, and adhere to the recommended diet and activity regimen. If you have chronic medical conditions, close coordination with specialized specialists is required. [34]

Childbirth and breastfeeding education classes are beneficial for expectant parents; participation in such classes increases their preparedness and skills for caring for a newborn. Information about available classes is usually provided during outpatient appointments. [35]

When planning work and leisure activities for late pregnancy, it is important to consider recommendations on flight safety, work schedules, and physical activity; discussing individual restrictions with your doctor is essential. [36]

Conclusion

The second trimester is a period of relative stability, active fetal growth, and the opportunity to conduct key screening tests. Timely visits, anatomical ultrasound, and screening for gestational diabetes form the core of monitoring during this period. [37]

Maintaining nutrition, physical activity, and promptly addressing any alarming symptoms can help reduce risks and prepare for the third trimester and future birth. Individual management strategies are determined by the mother's initial condition and local clinical guidelines. [38]