A 30-year-old woman, gravida 1 para 0, at 26 weeks gestation comes to the office for a routine prenatal visit. She has had no contractions, vaginal bleeding, or leakage of fluid. Fetal movement is normal. The patient has no chronic medical conditions, and her only medications are a prenatal vitamin and iron supplement. Prepregnancy BMI was 18 kg/m². She has gained less than the recommended 0.5 kg (1 lb) per week. Vital signs are normal. Fetal heart rate is 150/min. Fundal height is 24 cm. Ultrasound reveals a fetus measuring in the 25th percentile for gestational age. This patient is at increased risk for which of the following pregnancy-related complications?

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11ec25c8_d991_55d4_bc81_395480bb298b_MD0003_00 During pregnancy, women have increased nutritional requirements because both calories and nutrients (eg, folate, calcium, iron) are preferentially shunted to the developing fetus. To meet these metabolic demands, average women should increase their intake by approximately 350-450 kcal/day in the second and third trimesters. The target goals for gestational weight gain depend on prepregnancy BMI, which is an indicator of baseline maternal fat and nutrient stores. Patients with an underweight prepregnancy BMI (ie, <18.5 kg/m²) have low baseline stores and therefore require greater weight gain (~1 lb [0.5 kg]/week) to maintain a healthy pregnancy. ² This patient is both underweight and has had inadequate gestational weight gain, which along with the lagging fundal height (eg, 24 cm at 26 weeks gestation) and fetal growth in the 25th percentile suggest that this patient's nutrition may become insufficient for appropriate fetal development. This depleted state increases the risk for pregnancy-related complications, including preterm delivery (which occurs when patients can no longer shunt enough nutrients to support the fetus) and low birth weight (ie, small for gestational age infant). (Choices A and E) Women with a high prepregnancy BMI (eg, ≥30 kg/m²) and excessive gestational weight gain are at increased risk of cesarean delivery due to higher rates of gestational diabetes mellitus, fetal macrosomia, and labor dystocia. Obesity also increases the risk of hypertension and preeclampsia due to increased systemic vascular resistance. ² (Choice B) Unlike adult anemia, which is commonly due to iron deficiency (eg, inadequate nutrition, blood loss), fetal anemia typically occurs due to fetal red blood cell destruction (ie, hemolysis). Common causes include Rh alloimmunization, which is caused by maternal autoantibodies against fetal red blood cells, and parvovirus B19 infection, which is cytotoxic to fetal red blood cell precursors. (Choice C) Risk factors for placenta previa include prior cesarean delivery (due to uterine scarring) and multiple gestation (due to increased placental surface area). placenta previa (Choice D) Risk factors for placental abruption include abdominal trauma and conditions that disrupt the vascular integrity of the placenta (eg, maternal hypertension, smoking, cocaine use). Inadequate gestational weight gain is not associated with placental abruption. placental abruption Educational objective: Patients with an underweight prepregnancy BMI and inadequate gestational weight gain are at increased risk of pregnancy-related complications (eg, low birth weight, preterm delivery). References: Association of gestational weight gain with maternal and infant outcomes: a systematic review and meta-analysis. (http://www.ncbi.nlm.nih.gov/pubmed/28586887) Gestational weight gain outside the Institute of Medicine recommendations and adverse pregnancy outcomes: analysis using individual participant data from randomised trials. (http://www.ncbi.nlm.nih.gov/pubmed/31477075) Pregnancy weight gain by gestational age and stillbirth: a population-based cohort study. (http://www.ncbi.nlm.nih.gov/pubmed/29160923)

A 30-Year-Old Woman, Gravida 1 Para 0, at 26 Weeks