Pre-Natal Care

last authored: Aug 2011, David LaPierre
last reviewed: Sept 2011, Mario Elia





An auxiliary nurse and midwife (ANM), Rajasthan, India
© 2009 UNFPA/RN Mittal, India, Courtesy of Photoshare

While the primary objective of pre-natal care is to reduce maternal and fetal morbidity and mortality, it is also a unique opportunity to see women regularly and impact their health long term.


Prenatal care includes education, preventive health care, and identification and mitigation of risks to mother and child. Prenatal care can be provided by a number of individuals, including family doctor, nurse practitioner, obstetrician, midwife, or a combination of these.







Preparing for Pregnancy

It is important to have discussions about pregnancy during health visits. Topics should include nutrition, folic acid supplementation, substance use, and violence and abuse. Where available, all women in preconception and early conception periods should receive 0.4-0.8 mg folic acid starting three months before conception to prevent neural tube defects, while intermediate- or high-risk women (epilepsy, insulin-dependent diabetes, obesity, family history of neural tube defect, high-risk ethnic group) should receive 4-5 mg daily. Folic acid should be continued for 3 months post-partum. Women should be advised to avoid smoking, alcohol, and illegal drug use. A history of rubella and varicella infection or vaccination should be evaluated, with titres or immunization potentially required. Chronic health conditions such as diabetes, asthma, hypertension, heart disease, kidney disease, or depression should be optimized.

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Identifying Pregnancy

Signs of pregnancy include absence of menstrual period, breast tenderness and fullness, fatigue, nausea, and urinary frequency.

Biochemical testing is done by detecting the beta subunit of the human chorionic gonadotropin (hCG) in urine or blood. Home testing has a sensitivity of 75%, while clinical laboratory testing has a sensitivity between 97-100% for both blood and urine.

Blood tests are typically positive 9 days post-conception, while urine tests are usually positive 14 days post-conception. False-negative results usually follow testing too close to ovulation.

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The Initial Visit

The initial visit should occur within 12 weeks of the LMP, or earlier if the pregnancy is higher risk. It includes a complete history, physical examination, appropriate lab investigations, and counselling.

  • Gestational Age
  • History
  • Physical Exam
  • Counselling
  • Lab Investigations
  • Imaging

Gestational age is important to determine overdue status, for planning the birth and identifying the proper windows for screening. There are various ways of determining gestational age.


Last menstrual period (LMP)

An estimated date of delivery, or gestational age, can be determined by Nagele's Rule:

From the date (first day) of the LMP, add 7 days and subtract 3 months from women with 28-day cycles. Alternatively, add 9 months and 7 days to the LMP.

Cycle regularity is important if using dates; ask the patient about regularity and contraception.




If the patient is unsure of their LMP, the most accurate method is the earliest done ultrasound, if available. Accuracy decreases as pregnancy proceeds.

Mechanisms and accuracy of ultrasound testing includes:

  • first trimester uses crown-rump length. It is accurate +/- 3-5 days
  • second trimester uses biparietal (head) diameter. Accurate +/- 7 days
  • third trimester uses biparietal diameter. Accurate +/- 14 days


Clinical Assessment

Other means of assessing gestational age include:

  • fundal height
  • fetal heart beats (at 10 weeks via Doppler)
  • quickening, or first movement of the fetus noticed by the mother (at 17-18 weeks)




Begin with personal and demographic information to learn more about the patient as a person. Following this, proceed with:


Menstrual history

  • LMP to determine gestational age
  • period duration, regularity, severity
  • menarche
  • contraceptive use, type, and duration


History of current pregnancy

  • prenatal vitamins: esp. folic acid
  • nutrition, iron intake
  • bleeding/spotting/discharge
  • nausea/vomiting
  • fever
  • substance use (smoking, alcohol, illicit drugs)
  • occupational and environmental hazards


Past obstetrical history

Pregnancy history (ie G4P2A1)

gravida: number of pregnancies

parity: number of deliveries over 20 weeks,
regardless of outcome (twins, triplets, etc = 1)

abortion: number of deliveries under 20 weeks;
can be spontaneous or therapeutic

  • year, sex, weights, modes of deliveries, GAs, length of labour
  • location(s) of delivery
  • losses, complications, preterm
  • gestational diabetes and pregnancy-induced hypertension
  • previous cesarean section(s) (importantly, type of uterine scar present)
  • need for induction/augmentation, epistiotomy
  • lacerations
  • baby size and concerns after birth
  • breastfeeding


Past medical history and review of systems (optimize treatments)

  • gynecologic history (eg abnormal pap tests and treatments received)
  • hypertension
  • diabetes
  • heart disease
  • sexually transmitted infections
  • TORCH infections: toxoplasmosis, other (hepatitis B, syphilis, zoster, HIV, parvovirus B19) rubella, CMV, herpes
  • thyroid disease
  • depression
  • eating disorders
  • drugs, alcohol



  • prescription and nonprescription drugs
  • herbal medications


Immunizations and immunity, especially:

  • varicella (congenital varicella can be extremely damaging)
  • rubella


Family medical and genetic history

  • miscarriages
  • multiple gestations
  • congenital defects, developmental delay, genetic diseases


Social history

  • nutrition
  • physical fitness
  • smoking history
  • supports
  • domestic violence
  • work
  • finances
  • education
  • religion

Physical Exam

Physical exam is done to ensure current maternal health and predict any potential problems with the pregnancy.

  • weight, BMI, and blood pressure: important for interpreting subsequent values
  • pelvic exam, both with speculum and bimanually, to assess uterine size and architecture
  • head and neck exam (thyroid)
  • breast exam
  • heart and lungs
  • extremities (varicosities, swelling)
  • if appropriate, auscultate fetal heart (about 12 weeks onwards)


Where available, referral to perinatal classes should be offered and arranged.

Counselling should cover the following topics:

  • exercise, nutrition, weight gain, and obesity (see below)
  • smoking, alcohol, illicit drugs
  • work and travel
  • intercourse
  • social issues
  • genetic screening (where offered)
  • discussion about mode of delivery (vaginal, cesarean, vaginal birth after Cesarean)



Women should ideally have a pre-pregnancy weight of BMI <30; however, rates of obesity among women continue to increase worldwide. It is important to counsel women with regards to risks of obesity.


Maternal risks

  • fatigue
  • back pain, pelvic pain (can mask premature labour)
  • urinary tract infection
  • vascular disease and deep vein thrombosis
  • gestational hypertension/pre-eclampsia
  • gestational diabetes (4-fold increased rate of diagnosis)
  • cesarean delivery (often requiring vertical incision, instead of the safer horizontal incision)
  • difficulty with anaesthesia
  • post-partum infection
  • prolonged hospitalization: infections, difficulty feeding (mechanics, poor hormonal response)

Fetal risks

  • spontaneous abortion
  • fetal macrosomia, or low birth weight
  • neural tube defects
  • preterm birth
  • birth injury (shoulder dystocia, failed traction)
  • fetal demise, early neonatal death


Given the above risks, it is important to prepare for poor outcomes before, during, and after labour.

  • antenatal consultation with anaesthesiology, even if the mother is hoping for vaginal delivery
  • preparation for equipment required (especially for C-section)
  • continuous fetal monitoring during intrapartum
  • monitoring for risk of venous thromboembolism
  • monitoring for infection

Lab Investigations

Routine investigations often done during the prenatal period include:

  • CBC (anemia, thrombocytopenia)
  • ABO/Rh typing and antibody screening
  • rubella, syphilis (VDRL), hepatitis B, HIV testing

Other inital tests include:

  • pap testing (if none in the past 12 months); inform women of no increased risk of miscarriage
  • cervial smears for N. gonorrhea and Chlamydia
  • urine dipsticks for proteinuria and glycosuria

Urinanalysis is done, though dipsticks will miss up to 25% of asymptomatic bacteriuria (ASB). Urine culture should be done between 12-16 weeks, as this detects 80% of women with ASB during pregnancy. ASB occurs in 2-7% of pregnant women and can lead to pyelonephritis, low birth weight, and preterm delivery and therefore must be treated (Bachman et al, 1993).


A dating ultrasound should be carried out at 8-12 weeks gestation.


Ultrasound for anatomic survey and to confirm dates should be booked for 18-20 weeks. However, in obese women, this is better done at 20-22 weeks.

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Subsequent visits

Subsequent visits should occur every 4-6 weeks until 28 weeks, every 2 weeks until 36 weeks, and every week thereafter.

  • History
  • Physical Exam
  • Counselling
  • Lab Investigations


Calculate gestational age. If gestational age estimated from the 1st trimester ultrasound is more than 5 days apart from the age calculated from the LMP, the due date should be changed to reflect the dates based on ultrasound. If the 2nd trimester ultrasound is off by 10 days, the dates should also be changed to reflect this assessment.


Inquire as to

  • nausea/vomiting
  • cramping/contractions
  • bleeding/spotting; other discharge
  • fever
  • nutrition
  • fetal movements
  • smoking
  • other concerns, eg food, shelter, abuse, finances

If there is concern regarding mood disorders, the Edinburgh Postnatal Depression Scale is one of the most frequently used tools. It is a self-report questionnaire, translated into many languages. It is recommended to be used between 28-32 weeks.

Physical Exam

Pelvic exam may be done to assess cervical dilation and effacement as delivery approaches.


educational needs include:

  • heartburn
  • constipation
  • hemorrhoids
  • sexuality
  • breast feeding
  • circumcision
  • what is to come, ie labor, possibility of cesarian section
  • flu vaccine
  • toxoplasmosis: kitty litter and gardening

Lab Investigations

At each visit, urine dip for protein (kidney function) and glucose (gestational diabetes) should be carried out.

If significant leukocytes are seen on urinalysis, sending for urine culture may be helpful to rule out asymptomatic bacteuria (which must be treated).


Gestational diabetes

Done at 24-26 weeks. Provide 50g oral glucose challenge test. If the screen is >7.8 mmol/L at one hour, proceed to the 2 hour 75g gestational OGTT.


Antenatal Screening - 24-28 weeks

  • all women should be offered a diabetic screen and repeat HgB
  • HIV testing may be reoffered
  • women who are Rh- should have a repeat antibody screen if partner is Rh+ or unknown

Group B strep swabs of vagina and anus (first vagina, then anus). There is some debate about utility of universal screening, though is now recommended by Society of Obstetricians and Gynecologists of Canada at 35-37 weeks.

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Resources and References

World Health Organization - Report of Technical Working Group on Antenatal Care

Public Health Agency of Canada - Care During Pregnancy

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