What are the recommended care and precautions for a pregnancy in the first trimester?

First Trimester Pregnancy Care: Essential Recommendations

All women in the first trimester should take 400-800 µg of folic acid daily (or 5 mg if obese or diabetic), undergo comprehensive screening for diabetes, infectious diseases, and anemia, receive nutritional counseling focused on adequate protein intake without caloric excess, and establish baseline monitoring for complications including preeclampsia risk assessment. 1, 2

Supplementation Requirements

Folic Acid - Critical for Neural Tube Defect Prevention

• Standard dose: 400-800 µg daily starting preconceptionally and continuing through 12 weeks gestation 1, 3
• High-risk dose: 5 mg daily for women with obesity (BMI ≥30), diabetes, or previous NTD-affected pregnancy 1, 3
• This supplementation prevents 50% or more of neural tube defects including spina bifida and anencephaly 4, 5
• Must be taken as supplement—dietary folate alone cannot achieve protective red blood cell folate levels 6

Vitamin and Mineral Supplementation

• Prenatal multivitamin containing 150 mg potassium iodide should be started before conception 1
• Vitamin D supplementation to maintain serum levels above 50 nmol/L, with calcium added as needed 1
• Vitamin B12 monitoring every trimester with supplementation of 1 mg intramuscularly every 3 months if deficiency identified 1, 7
• Iron supplementation based on serum ferritin and iron studies checked every trimester 1, 2

Critical Vitamin A Warning

• Avoid all vitamin A in retinol form during first 12 weeks—excess retinoic acid is teratogenic 1, 3
• Switch to beta-carotene form of vitamin A, which is safe 1, 3

Essential Laboratory Screening

First Trimester Blood Work

• Complete blood count to assess for anemia, repeated every trimester 1, 2
• Blood group and Rh typing to identify need for Rh immunoglobulin prophylaxis 2
• Serum ferritin and iron studies (transferrin saturation) checked every 3 months 1
• Serum folate and vitamin B12 checked every 3 months 1, 7

Diabetes Screening - Highest Priority

• Early screening for pre-existing type 2 diabetes using fasting plasma glucose or HbA1c in all women with risk factors 1
• Women with pre-existing diabetes require HbA1c monitoring every 3 months throughout pregnancy 1
• Target HbA1c <6.5% before conception and during pregnancy to minimize congenital anomalies 1

Infectious Disease Panel

• Hepatitis B surface antigen (HBsAg) testing 2
• HIV screening offered to all pregnant women 2
• Syphilis and sexually transmitted infection screening 1, 2
• Thyroid function testing in women with risk factors or symptoms 1

Nutritional Guidance

Energy and Macronutrient Requirements

• No increase in caloric intake during first trimester unless woman has depleted body reserves 1, 3
• Protein intake: minimum 60 g/day (0.75 g/kg plus additional 10 g/day) 1, 3
• Avoid hypocaloric diets <1,200 calories/day—these cause ketonemia and ketonuria which may harm fetal development 3
• Expected weight gain: 1.4-2.3 kg during first trimester for normal-weight women 3

Dietary Restrictions - Non-Negotiable

• Complete alcohol abstinence—no amount is safe during pregnancy 1, 3
• Avoid raw animal products, soft cheeses, and unpasteurized foods to prevent foodborne illness 3
• Eliminate caffeinated and alcoholic beverages if experiencing dumping syndrome (post-bariatric surgery patients) 1
• Abstain from nicotine products, recreational drugs including marijuana 1

Ultrasound and Aneuploidy Screening

Dating and Structural Assessment

• Dating ultrasound in first trimester to establish accurate gestational age 2
• Nuchal translucency measurement between 11 weeks 4 days and 13 weeks 6 days as part of combined first-trimester screening 2
• For women with BMI >40, consider early anatomy scan at 14-16 weeks to overcome acoustic window limitations 1

Chromosomal Screening Options

• First-trimester combined screening (nuchal translucency + biochemical markers) achieves 85-92% detection rate for Down syndrome 2
• Cell-free DNA screening offers higher sensitivity where cost permits 2

Preeclampsia Risk Stratification and Prevention

High-Risk Factors Requiring Aspirin Prophylaxis

• Advanced maternal age >35 years 2
• Obesity (BMI ≥30) 1, 2
• Pre-existing diabetes mellitus 2
• Chronic hypertension 2
• Previous preeclampsia 2

Aspirin Prophylaxis Protocol

• Low-dose aspirin 75-81 mg daily starting at 12 weeks gestation for women with high-risk factors 2
• Women with BMI ≥35 may take up to 180 mg daily if gastrointestinal bleeding risk is low 1
• Continue until delivery 2

Special Population Considerations

Post-Bariatric Surgery Patients

• Nutritional screening every trimester: full blood count, serum ferritin, iron studies, folate, B12, vitamin A, vitamin D with calcium/phosphate/magnesium/PTH 1
• Additional first trimester screening: vitamin E, zinc, copper, selenium 1
• Thiamine 300 mg daily with vitamin B complex if vomiting occurs—prolonged vomiting requires IV supplementation 1
• Weekly oral vitamin K if deficiency noted with coagulation defect 1

Women with Pre-existing Diabetes

• Dilated eye examination in first trimester to assess for diabetic retinopathy, then every trimester 1
• Discontinue ACE inhibitors, ARBs, and statins immediately—these cause fetal renal anomalies and death 1
• Switch oral antidiabetic agents to insulin; metformin may be continued 1
• Capillary blood glucose monitoring or continuous glucose monitoring if HbA1c ≥6.5% or fasting glucose ≥7.0 mmol/L 1

Women with Hypothyroidism

• Thyroid replacement dosages typically increase by 30% or more by 4-6 weeks gestation 1
• Inadequately treated hypothyroidism in first trimester causes cognitive impairment in children 1

Common Pitfalls to Avoid

• Do not withhold food to control blood glucose—this harms fetal growth and development 1
• Do not recommend weight loss during pregnancy unless specific medical indications exist 1
• Do not delay switching teratogenic medications (warfarin, ACE inhibitors, ARBs, isotretinoin, valproate)—change before conception or immediately upon pregnancy confirmation 1
• Do not assume multivitamins contain adequate folic acid—verify dose and supplement separately if needed to reach target 1, 3
• Do not screen for gestational diabetes at 12 weeks unless high-risk factors present—standard screening occurs at 24-28 weeks 2