Prenatal examination is the clinical examination of the pregnant woman and the fetus during pregnancy. Due to the growth and development of the fetus, a series of adaptive changes occur in the body systems of the pregnant woman, and if they go beyond the physiological range or if the pregnant woman herself suffers from a disease that cannot adapt to the changes of pregnancy, both the pregnant woman and the fetus may develop pathological conditions. Through prenatal checkups (hereinafter referred to as obstetric checkups), it is possible to detect and prevent comorbidities (pre-existing diseases of pregnant women such as heart disease) and complications (diseases occurring after pregnancy such as gestational hypertension syndrome), correct abnormal fetal position and detect fetal abnormalities in time, and determine the mode of delivery.
1.First maternity examination (6~8 weeks of pregnancy)
(1) Ultrasound examination
To determine whether the pregnancy is normal intrauterine pregnancy; for pregnant women with irregular menstrual cycles, use this ultrasound to determine the gestational age.
(2) Bad lifestyle screening
Pregnant women who smoke can lead to low birth weight babies, and their probability of spontaneous abortion and preterm delivery is increased. Newborns exposed to smoking are prone to increased incidence of upper respiratory tract infections and sudden infant death syndrome, and should be advised to quit, but there is insufficient evidence to support the use of medication for abstinence during pregnancy. Alcohol is a clear teratogen and is harmful to the fetal face as well as to the development of the central nervous system. Although there is a clear dose-dependence between the two, there are no clearly stated safety thresholds for alcohol use during pregnancy. Illegal drug use and injection during pregnancy is harmful to fetal health and development, increasing the risk of preterm birth and fetal growth restriction in late pregnancy, maternal addiction, human immunodeficiency virus (HIV) infection, and hepatitis. After the birth of the fetus, there is an increased risk of neonatal withdrawal symptoms and consequent developmental delays, learning disabilities, and behavioral problems. Periodic screening for the use of prohibited drugs should be performed.
(3) Blood and urine routine and liver and kidney function screening
Routine blood and urine tests and liver and kidney tests should be performed during the first obstetric examination, and pregnant women with abnormal results or related high-risk factors should be rechecked in the middle and late pregnancy. The National Institute for Clinical Excellence (NICE) recommends that routine urine tests should be performed at every maternity visit to assess the risk of developing hypertensive disorders in pregnancy in combination with blood pressure and urine protein values.
(4) Oral examination
Periodontal disease is an inflammatory oral disease associated with preterm delivery, which can cause bacteremia and pathogenic bacteria leading to infection of the reproductive tract, thus triggering preterm delivery. There have been many epidemiological studies supporting the relationship between periodontal disease and preterm birth, which is closely related to low birth weight babies. However, oral anaerobic periodontal disease is currently an under-recognized risk factor in China. Therefore, women of childbearing age should undergo oral examination before and during pregnancy.
(5) Screening for Rh and ABO blood groups
A complete set of maternal blood groups should be tested during the first obstetric examination. In the case of Rh blood group incompatibility, only 1%-2% of cases occur in the first newborn; while 40%-50% of ABO blood group incompatibility occurs in the first child, but the symptoms are generally mild and rarely cause serious fetal sequelae (such as stillbirth, hydrops fetalis, severe anemia, etc.), except for a very small number of severe cases requiring intrauterine treatment, the majority of children with ABO hemolytic disease are treated after birth.
(6) Hepatitis B screening
The combination of hepatitis B in pregnancy can lead to preterm delivery, liver failure, and perinatal vertical transmission. Pregnant women with high-risk factors (such as intravenous drug use, history of hepatitis B contact, sexually transmitted diseases, tattoos, history of blood transfusion, etc.) should be screened repeatedly during pregnancy.
(7) HIV screening
It is controversial whether HIV infection increases adverse pregnancy outcomes. The American College of Obstetricians and Gynecologists (ACOG) reports that asymptomatic HIV-infected pregnant women do not have an increased risk of developing various pregnancy complications. However, immunosuppression during late pregnancy may accelerate the progression from asymptomatic to AIDS in HIV-infected patients.
(8) Screening for reproductive tract infection (RTI) during pregnancy
In recent years, RTI is increasing in China, including bacterial vaginosis, trichomoniasis, vaginal pseudomonal yeast disease, Chlamydia trachomatis infection, gonorrhea, condyloma acuminata, syphilis, etc., all of which are harmful to mother and child and may lead to premature rupture of membranes, intra-amniotic infection (IAI), fetal growth restriction (FGR), postpartum infection and neonatal infection. Therefore, routine screening for RTI is recommended.
(9) Cervical cytology examination
The incidence of cervical cancer in China is increasing year by year and tends to be younger, so it should be given sufficient attention. Cervical cytology should be performed before pregnancy or the first obstetric examination, and colposcopy and local biopsy should be considered according to the results. For cervical lesions in pregnancy, if cervical cancer is ruled out, the principle is not to treat them during pregnancy, but to delay the review until 6-8 weeks after delivery, and then decide the follow-up treatment according to the results.
2.Early and mid-term prenatal checkups (10~27 weeks of gestation)
(1) Establishment of perinatal health care manual (10~12 weeks of gestation)
(2) Prenatal screening (11~20 weeks of gestation)
Ultrasound measurement of fetal nuchal translucency thickness (NT) or NT combined with Down’s I (β-HCG and pregnancy-associated plasma protein A) between 11 and 13+6 weeks of gestation can improve the detection rate of Down’s syndrome.
In the middle of pregnancy (15-20 weeks), screening for Down’s II (AFP, β-HCG, μE3) should be performed. If the screening is positive, systemic ultrasound should be performed to assess the risk and decide whether invasive prenatal diagnosis is needed in combination with the pregnant woman’s own condition (whether she has high-risk factors, family history, etc.).
(3) Fetal systemic ultrasound (20~24 weeks of gestation)
Systemic ultrasonography can help to detect fetal structural abnormalities, and soft indicators of fetal ultrasonography (such as NT thickening, mild dilatation of bilateral renal pelvis, choroidal cyst, intraventricular strong echogenicity, enhanced intestinal echo, mild widening of lateral ventricle, etc.) can help to screen for fetal chromosomal abnormalities.
(4) Amniocentesis (16~22 weeks of gestation)
The reliability of amniocentesis in diagnosing chromosomal abnormalities is greater than 95%. Amniocentesis should be performed at 16 to 22 weeks of gestation for those who are at high risk on serologic screening, older than 35 years old, who have previously given birth to a child with a birth defect, who have a family history of birth defect delivery, and who have a birth defect in themselves or their husbands.
(5) Umbilical vein puncture (22~30 weeks of gestation)
Umbilical cord blood puncture is suitable for mid- to late-term pregnancies, but it is technically demanding and has a greater chance of causing complications such as placental abruption, amniotic fluid embolism, subcutaneous hematoma and fetal injury than amniocentesis. However, it can be used for rapid karyotyping, intrauterine diagnosis of fetal infections and fetal hematologic disorders, and intrauterine transfusion treatment of fetal hemolytic anemia.
3.Prenatal examination in late pregnancy (28~41 weeks of gestation)
(1) Gestational diabetes mellitus (GDM) screening (24~28 weeks of gestation)
The 50g glucose screening should be performed at 24~28 weeks of gestation, and those with normal 50g glucose screening can be rechecked at 32~34 weeks of gestation, the period with the most obvious changes in glucose metabolism, or any time when the pregnant woman has signs and symptoms of hyperglycemia, in order to avoid missing the diagnosis. Based on the results of fasting glucose and 50g glucose screening, we will decide whether to do further 75g glucose tolerance test (OGTT).
(2) Review blood and urine routine and liver and kidney function (28~30 weeks of pregnancy)
During this period, it should be reviewed to assess the presence of anemia, hypertensive disorders in pregnancy, and impairment of liver and kidney function, in conjunction with the results of the early examination.
(3) Evaluation and prediction of preterm labor (28-34 weeks of gestation)
During this period, we should ask for signs or symptoms of preterm labor, determine if there are any risk factors for preterm labor, and provide counseling including early clinical signs and appropriate management. The incidence of preterm labor can be predicted by ultrasound examination of the length of the cervix and the opening of the endocervix combined with the measurement of fetal fibronectin (fFN) in the posterior vaginal fornix. However, there is insufficient evidence to support routine screening of all pregnant women. Screening is recommended for pregnant women with a history of preterm labor.
(4) Determination of placental position, fetal previa and fetal orientation (31~32 weeks of gestation)
Ultrasonography can determine the placenta position, fetal previa, fetal orientation, and amniotic fluid volume. It can also further evaluate the size and development of the fetus.
(5) 35~41 weeks of gestation
We will perform one check-up every week, including blood pressure, electronic fetal heart monitoring (NST), fetal umbilical blood flow check, ultrasound monitoring of amniotic fluid volume, cervical maturity check, etc.
(6) Over 41 weeks of gestation
The risk of fetal distress and fetal death is increased in overdue pregnancies. Hospitalization is needed for delivery.
4. Contents of routine prenatal checkups
(1) Weight measurement (weekly)
Each prenatal checkup should measure the weight of the pregnant woman and calculate the body mass index (BMI).
(2) Fetal heart sound auscultation (after 14 weeks of gestation)
From 14 weeks of gestation, the fetal heartbeat should be listened to at every antenatal checkup. If the fetal heartbeat is too fast or too slow, it may indicate fetal distress. The initial auscultation is also psychologically beneficial to the parents.
(3) Measurement of uterine height and abdominal circumference (after 20 weeks of gestation)
The growth of uterine height and abdominal circumference is an indication of fetal growth. If the uterine height and abdominal circumference do not correspond to the gestational weeks, especially from 20 to 36 weeks of gestation, it often indicates abnormal fetal growth or abnormal amniotic fluid volume. It is recommended to test the uterine height and abdominal circumference at each delivery in the middle and late stages of pregnancy.
(4) Screening for hypertensive disorders in pregnancy (after 20 weeks of gestation)
Blood pressure measurement and urine examination can help to diagnose hypertension in pregnancy at an early stage.
(5) Fetal movement count (after 30 weeks of gestation)
Pregnant women should count the fetal movements since 30 weeks of pregnancy, at the fixed time of morning, noon and night for 1h each day, or multiply the sum of 3 fetal movements in morning, noon and night by 4, which is the number of fetal movements in 12h.
(6) Pregnancy exercise education
In recent decades, the attitude towards exercise during pregnancy has changed significantly. Moderate and regular exercise during pregnancy is safe and beneficial.
(7) Nutritional guidance during pregnancy
Nutritional supply during pregnancy is very important for pregnancy, not only to ensure the normal metabolic needs of pregnant women, but also necessary for the development of the fetus. However, blind nutritional supplementation during pregnancy may not only lead to an increase in pregnancy complications (gestational diabetes, gestational hypertension, and giant babies), but also increase the rate of cesarean section and obstructed labor. It is recommended to provide reasonable and individualized nutritional guidance to pregnant women during prenatal checkups to effectively reduce the adverse effects of nutritional factors on mother and child.