A 26-year-old woman, gravida 2 para 1, comes to the office for an initial prenatal visit. She has had daily nausea and multiple food aversions but no vomiting or weight loss. The patient has no known medical conditions and takes no daily medications or prenatal vitamins. Her last pregnancy was 2 years ago, and she did not receive prenatal care. That pregnancy ended at term with a vaginal delivery of an infant weighing 4.6 kg (10.1 lb). Since the delivery, the patient has had some irregular menstrual bleeding and is unsure of her last menstrual period. Temperature is 36.7 C (98.1 F), blood pressure is 132/84 mm Hg, and pulse is 78/min. BMI is 30 kg/m2. Pelvic examination shows an enlarged, nontender uterus. Pelvic ultrasound reveals a 10-week intrauterine pregnancy with normal cardiac activity. Urinalysis is negative for protein, glucose, and ketones. In addition to ordering routine prenatal laboratory tests, which of the following is the best next step in management of this patient at this visit?
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Gestational diabetes mellitus (GDM) is common and is associated with obstetric complications (eg, stillbirth, shoulder dystocia, preeclampsia). Therefore, all pregnant patients require GDM screening with a 1-hr glucose challenge test (GCT); this is usually performed at 24-28 weeks gestation when maternal insulin resistance increases physiologically due to placental release of diabetogenic hormones.
However, early screening for undiagnosed pregestational diabetes mellitus (eg, GCT at the initial prenatal visit) is indicated for high-risk patients with obesity plus ≥1 of the following:
Identifying undiagnosed pregestational diabetes mellitus during early pregnancy can help optimize glucose control and decrease the risk of pregnancy complications. Even if the early screening test is normal, a repeat 1-hr GCT is performed at 24-28 weeks gestation.
(Choice A) The tetanus-diphtheria-pertussis (Tdap) vaccine protects against pertussis, which has high infant morbidity and mortality. Maternal vaccination occurs at 27-36 weeks gestation to maximize transplacental antibody transfer for fetal protection. Early (eg, initial prenatal visit) or late maternal vaccination results in suboptimal fetal protection.
(Choice B) Serial quantitative β-hCG levels are obtained for pregnancies of unknown location (ie, positive hCG but no visible intrauterine or extrauterine pregnancy); abnormally rising levels suggest an abnormal or ectopic pregnancy. This patient has a 10-week intrauterine gestation on ultrasound; additional β-hCG levels would not change management.
(Choice C) Progesterone, initially secreted by the corpus luteum, maintains early pregnancy. Low progesterone levels may occur due to corpus luteum removal (eg, oophorectomy for ovarian torsion), abnormal intrauterine pregnancy, or ectopic pregnancy. Progesterone levels, whether they are low or not, would not change management in a normal intrauterine pregnancy.
(Choice D) Nausea and vomiting are common during pregnancy. In women with mild nausea and vomiting (as in this patient with nausea without vomiting), changes in vital signs, or weight loss, the initial approach is conservative treatment with dietary changes or vitamin B6 (pyridoxine) prior to prescribing antiemetic medications.
Educational objective:
All pregnant patients require gestational diabetes mellitus screening at 24-28 weeks gestation. However, earlier screening (eg, at the initial prenatal visit) is recommended in patients with obesity and additional risk factors for undiagnosed pregestational diabetes mellitus (eg, prior macrosomic infant, polycystic ovary syndrome).