Antepartum care (second trimester): Clinical sciences

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Introduction0:00–0:44

Second trimester antepartum care refers to pregnancy care from 14 weeks of gestation through 27 weeks and 6 days of gestation.
It is critical that patients receive appropriate care during this time of rapid fetal growth and development to prevent complications and optimize pregnancy outcomes.
During this time, all patients in the second trimester warrant an obstetrical ultrasound; genetic counseling; screening for abdominal wall and open neural tube defects; gestational diabetes screening; consideration of repeat antibody screening; and trimester-specific pregnancy education.When assessing a patient presenting for a second trimester antepartum visit, your first step is to obtain a focused history and physical.

Focused H&P0:44–1:56

The history may reveal common symptoms, such as nausea, vomiting, heartburn, and round ligament pain. Patients may report feeling fetal movement once around 20 weeks, but it may be as early as 16 weeks; this is called quickening.
It’s also important to review aspects of the first trimester history, like rescreening for depression, anxiety, and intimate partner violence at least once per trimester.Your focused physical should include reviewing weight, as both insufficient and excess weight gain can result in complications.
Trend blood pressure as well, as two or more elevations prior to 20 weeks suggest chronic hypertension, and after 20 weeks it could indicate gestational hypertension.
Perform fetal heart rate Doppler assessment at each visit. Starting at 20 weeks of gestation, include a fundal height to track uterine growth, as well to screen for macrosomia and growth restriction.With the history and physical complete, it’s time to initiate second trimester antepartum care.

Obstetric US1:56–4:43

Perform an obstetric ultrasound between 18 and 22 weeks of gestation. During this ultrasound, assess the cervical length, placental location, and fetal anatomy.
A short cervical length of less than 25 mm may indicate an increased risk of preterm birth. Vaginal progesterone could be considered as a treatment option for patients with a shortened cervix who also have a history of preterm birth and singleton gestation.
Also, examine placental location in the uterus, such as anterior or posterior, and to evaluate for placenta previa or vasa previa.
A complete survey of fetal anatomy allows for counseling and delivery at an appropriate facility if there is an anomaly.
Some patients may have had their due date established or confirmed by a first trimester ultrasound; however, if no prior ultrasound has been performed, the second trimester ultrasound can be used to confirm dates.
Now, if there is evidence of early onset growth restriction at the time of the fetal anatomic survey, a follow up growth ultrasound should be obtained about 4 weeks later.
Additionally, if there is a high risk of a fetal cardiac defect, like in patients with pregestational diabetes, or in those with a prior child affected by a cardiac defect, refer for a fetal echocardiogram.
This will give you more detailed views of the heart than the standard fetal anatomic survey. Also, if all views cannot be seen on the anatomy ultrasound or abnormalities are noted, repeat imaging may be done later in the second trimester as a follow up.
Here's a clinical pearl! In the second trimester, the due date is determined by comparing the gestational age calculated by the last menstrual period to fetal biometry, meaning an assessment of the fetal head, abdomen, and extremities.
For pregnancies between 14 weeks and 15 weeks 6 days, assign a new due date if the gestational age by ultrasound is more than 7 days off from menstrual dates.
Between 16 weeks and 21 weeks and 6 days, redate the pregnancy if measurements are more than 10 days different. If the patient is between 22 weeks and 27 weeks and 6 days, adjust the due date if measurements are more than 14 days apart.
Remember, the earliest ultrasound is the most accurate to determine the due date! So, if a prior ultrasound has been performed, use that first ultrasound to establish the due date, and don’t redate based on a later ultrasound.Next up is genetic counseling for all patients.

Genetic Counseling4:43–6:04

This means presenting options for both screening and diagnostic testing. Many patients had this testing done in the first trimester, and if so, there is no need to repeat it.
But if not, cover this in the second trimester. For diagnostic testing, amniocentesis is performed any time after 15 weeks of gestation.
Amniocentesis, like chorionic villus sampling in the first trimester, looks not only for fetal aneuploidies but also disorders of single genes, such as DiGeorge syndrome or achondroplasia.
There are also noninvasive screening tests that focus on aneuploidies. The quad screen is a blood test that looks at alpha fetoprotein, human chorionic gonadotropin, unconjugated estriol, and inhibin A levels in maternal blood.
The timing of testing is usually between 15 and 22 weeks. Non-invasive prenatal testing, or NIPT, is another screening option that looks for aneuploidies and sex chromosome disorders by examining cell-free fetal DNA in the maternal blood.
Typically NIPT is performed in the first trimester, but it can be done at any time during the pregnancy. Next, let’s go over screening for abdominal wall and open neural tube defects.

Screening for Abdominal Wall and Open Neural Tube Defects6:04–7:31

As a quick review, alpha fetoprotein, or AFP, produced by the fetal liver and excreted into the amniotic fluid, passes through the placenta and enters maternal circulation.
An open neural tube defect or gastroschisis can lead to extra leakage of AFP into the amniotic fluid, which then results in elevated levels of maternal serum alpha fetoprotein, or MSAFP.
Normal MSAFP values don’t exclude closed neural tube defects, because the overlying tissues prevent the AFP from leaking.
It’s worth pointing out that MSAFP is included in a second trimester quad screen, but not in the first trimester screen, or in the NIPT.
That means for patients who choose NIPT, chorionic villus sampling, or no genetic testing at all, you should still offer testing for open defects with an MSAFP.
MSAFP is only a screening test and requires follow-up with ultrasound for direct visualization of the abdomen, spine, and skull.
Because today’s images are such high quality, some patients may skip the MSAFP and prefer only examination of these structures on their routine fetal anatomic survey.An incredibly important part of the second trimester is gestational diabetes screening with a one-hour oral glucose tolerance test or OGTT.

Screening for Gestational Diabetes7:31–8:25

Patients who have pregestational diabetes should not undergo this second trimester test. All others, including those who may have passed a first-trimester gestational diabetes screen, should have this done between 24 and 28 weeks.
This involves drinking a liquid containing 50 grams of glucose and checking blood glucose an hour later. If a patient’s 1-hour screening test is elevated, order the 3-hour diagnostic test.
The 3-hour test starts with a fasting glucose level, followed by checking blood glucose levels 1, 2, and 3 hours after consuming a 100-gram glucose load.
If two or more values are abnormal, diagnose gestational diabetes. Let’s move on to second trimester antibody screening.

Antibody Screen8:25–9:35

All patients with an Rh-negative blood type need antibody screening between 24 and 28 weeks, and should receive a single dose of Rh immune globulin at 26 to 28 weeks gestation to prevent alloimmunization in future pregnancies.
It’s important to remember that giving Rh immune globulin will cause a positive antibody screen for up to 10 to 12 weeks, so be sure to draw the patient’s blood before giving the medication.
If antibody screening is negative, you can go ahead and give Rh immune globulin. Here’s a high-yield fact!
Rh Immune globulin offers antibody protection for about 12 weeks. That’s why it’s best to give it at 28 weeks, to cover the pregnancy until they are 40 weeks of gestation.
However, if an Rh-negative patient has received Rh immune globulin earlier in the second trimester for indications like antenatal vaginal bleeding, amniocentesis, or abdominal trauma, wait 12 weeks to give a second dose.Last but not least, counsel patients on general expectations.

Pregnancy Education9:35–10:23

The tetanus, diphtheria, and acellular pertussis, or Tdap vaccine, is recommended for all pregnant patients as early as 27 weeks, regardless of when they received it last.
Maternal antibodies cross the placenta and will protect the fetus until they can be vaccinated after birth. It’s also important to review the warning signs and symptoms of preterm labor and preeclampsia.
Educate patients on expectations for the second trimester, including common aches and pains like round ligament and lower back pain.
Finally, be sure to review indications for calling labor and delivery, including contractions, leaking fluid, vaginal bleeding, and decreased fetal movements.
Alright, as a quick recap… Second trimester antepartum care occurs from 14 weeks gestation through 27 weeks and 6 days gestation.

Review10:23–11:09

Obstetric ultrasound should be done to assess cervical length, placental location, and fetal anatomy. Genetic counseling should be covered if not done in the first trimester and screening for open neural tube and abdominal wall defects should be offered.
Gestational diabetes screening should be done and for Rh-negative patients, an antibody screen should be performed and Rh immunoglobulin administered.
Lastly, it’s important to educate patients about the need for Tdap vaccination, warning signs, and expectations.
Antepartum care (second trimester): Video, Steps | Osmosis