Evidence based prenatal care
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Evidence-Based Prenatal Care. Carolyn Halley, MD August 2006. Goals. How strong is the evidence for our prenatal standards of care? What areas of prenatal care are controversial? In which areas is there important ongoing research?. Providers.

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Evidence-Based Prenatal Care

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Evidence based prenatal care

Evidence-Based Prenatal Care

Carolyn Halley, MD

August 2006



  • How strong is the evidence for our prenatal standards of care?

  • What areas of prenatal care are controversial?

  • In which areas is there important ongoing research?



  • Caregiver continuity during the antenatal period has been associated with reduced interventions in labor and improved maternal satisfaction. (A-UK)

  • Care provided by midwives, family physicians, and obstetricians was found to be equally effective, although women were slightly more satisfied with care from midwives and family physicians. (A-UK)

Number of visits

Number of Visits

  • Women in the US typically attend regular prenatal visits, usually 7-14 times per pregnancy.

  • For a woman who is nulliparous with an uncomplicated pregnancy, a schedule of ten appointments should be adequate. For a woman who is parous with an uncomplicated pregnancy, a schedule of seven appointments should be adequate. (B-UK)

Edc determination

EDC Determination

  • A Cochrane review in 1998 found that U/S before 24 weeks resulted in earlier detection of multiple pregnancies and reduced rates of induction of labor for post-term pregnancy.

  • In a 1996 study of over 34,000 pregnancy records, EDC based on U/S before 20 weeks instead of certain LMP reduced induction rates by 70%.

Edc determination1

EDC Determination

  • “In health systems in which reliable early pregnancy U/S is available at an acceptable cost, it should be performed routinely and the EDC should be revised, to avoid unnecessary induction of labour for a mistaken diagnosis of post-term pregnancy.” (Cochrane 1997)

  • “Pregnant women should be offered an early ultrasound scan to determine gestational age (in lieu of LMP for all cases) and to detect multiple pregnancies.” (A-UK)

Routine monitoring urine dipstick

Routine Monitoring—Urine Dipstick

  • BP every visit (C-US)

  • Whenever blood pressure is measured, urine dipstick should be tested for proteinuria. (C-UK/US)

  • A meta-analysis published in 2005 showed screening for GDM and pre-eclampsia using urine dipsticks for glycosuria is ineffective with low sensitivities and low PPV.

Routine monitoring urine dipstick1

Routine Monitoring—Urine Dipstick

  • Recommendation from this meta-analysis is to perform a urinalysis ONLY at the first prenatal visit in low-risk women. (B-US).

  • USPSTF advises testing for proteinuria only with high BP.

  • The US Institute for Clinical Sx Improvement, and Canadian an Australian health groups recommend against routine urine testing.

  • ACOG advises that there is no reliable predictive test for preeclampsia and is silent on glycosuria.

Routine monitoring

Routine Monitoring

  • Maternal height and weight should be measured at first antenatal visit to determine BMI. (B-US)

  • Measurement of the uterine fundus to assess fetal growth at each visit (B-US, A-UK)

Routine monitoring1

Routine monitoring

  • Auscultation of the fetal heart tones after 10 wks at each visit, to confirm viability only. (C-US, D level evidence recommends against routine auscultation, except to reassure mother).

  • Routine antenatal pelvic examination does not accurately assess gestational age or accurately predict preterm birth or CPD and is not recommended. (B-UK)

Anticipatory guidance

Anticipatory Guidance

  • Breastfeeding is best for most infants. (B-US)

  • Hot tubs and saunas probably should be avoided during the first trimester (A-US)

  • Sexual intercourse during pregnancy is not associated with adverse outcomes. (B-US)

  • Moderate exercise may be initiated or continued (A-UK). Scuba diving and activities with risk of fall are not recommended. (C-US)

Anticipatory guidance1

Anticipatory Guidance

  • Prolonged standing and exposure to certain chemicals are associated with pregnancy complications. (B-US)

  • Pregnant women should be informed about the specific risks of smoking during pregnancy. The benefits of quitting at any stage should be emphasized. (A-US/UK)

Anticipatory guidance alcohol

Anticipatory Guidance- Alcohol

  • There is no known safe amount of alcohol consumption during pregnancy. Abstinence is recommended. (B-US).

  • Excess alcohol has an adverse effect on the fetus. Therefore it is suggested that women limit alcohol consumption to no more than one standard unit per day. (C-UK)

Dietary guidelines

Dietary guidelines

  • Moderate amounts (1-2 cups coffee) of caffeine are probably safe. (B-US)

  • Pregnant women should avoid shark, swordfish, kind mackeral and tilefish, and tuna steaks and should limit intake of other fish (including canned tuna) to 2-3 meals per week. (B-US)

  • Soft chese (feta, brie, bleu) should be avoided (C-US)

  • Lots of other C-level evidence on artificial sweeteners, raw eggs, herbal teas, etc.



  • Begin folic acid supplementation at least 1 month before conception. (A-US/UK)

  • Be screened for anemia and treated with iron if necessary. (B-US/UK). Iron supplementation should NOT be offered routinely to all pregnant women. (A-UK)

  • Pregnant women should limit vitamin A intake to < 5000 IU/day. (B-US, ~C-UK)

Infectious disease

Infectious Disease

  • Routine screening for active Hep B, syphilis, and HIV (A, A, B-US; A, B, A-UK)

  • Routine screening (and tx) for asymtomatic bacteriuria by urine culture at 12-16 wks. (A-US/UK)

  • Routine screening for BV is not recommended. (A-US/UK)

  • All asx pregnant women aged </= 25 years & others at increased risk should be screened for chlamydial infection. (B-US)

Infectious disease1

Infectious Disease

  • After a significant varicella or zoster contact, a susceptible pregnant women (regardless of gestational age) should be given VZIG (up to 10 days after contact). (B-UK)

  • Routine antenatal screening for HSV 1/2 antibodies is not recommended. (B-UK) Pregnant women contracting HSV during pregnancy or those with frequent outbreaks should receive acyclovir beginning at 36 weeks. (C-UK)

Infectious disease2

Infectious Disease

  • US standard of care is to test all pregnant women for GBS by vaginorectal cx at 35-37 wks and treat colonized women with IV abx at labor or 18 hrs ROM.

  • This recommendation by CDC and ACOG is based on a nonramdomized, pop-based study from 2002.

  • Pregnant women should NOT be offered routine antenatal screening for GBS based on insufficient evidence. (C-UK) However, women with GBS positive urine or with a h/o having a GBS infected infant in the past should receive antibiotics. (C-UK)

  • Canadian TF on Preventative Health Care recomends universal screening with selective tx of colonized women who also have clinic risk factors.

Gdm screening

GDM Screening

  • The USPSTF found fair to good evidence that screening combined with diet and insulin therapy can reduce the rate of fetal macrosomia in women with GDM.

  • However, it found insufficient evidence that screening for GDM substantially reduces important adverse health outcomes for mothers or their infants (for example, cesarean delivery, birth injury, or neonatal morbidity or mortality).

  • According to the Agency for Healthcare Research and Quality the NNS to prevent one brachial plexus injury is about 3,300-8,900

Gdm screening1

GDM Screening

  • The USPSTF concludes that the evidence is insufficient to recommend for or against routine screening for gestational diabetes.

  • The evidence does not support routine screening for GDM and therefore it should not be offered. (B-UK)

  • The National Institute for Child Health and Human Development is currently sponsoring an RCT on GDM screening involving approximately 2,400 women.

Evidence based prenatal care


  • Cesarean delivery on maternal request (CDMR) compared with planned vaginal delivery (PVD). Virtually no studies exist on CDMR, so the knowledge base rests chiefly on indirect evidence from proxies possessing unique and significant limitations. Furthermore, most studies compared outcomes by actual routes of delivery, resulting in great uncertainty as to their relevance to planned routes of delivery. Our comprehensive assessment, across many different outcomes, suggests that no major differences exist between primary CDMR and PVD, but the evidence is too weak to conclude definitively that differences are completely absent. Given the limited data available, we cannot draw definitive conclusions about factors that might influence outcomes of planned CDMR versus PVD. (USPSTF March 2006)

At term

At term

  • Abdominal palpation should be used to assess fetal presentation beginning at 36 weeks. (B-US/C-UK)

  • Antenatal perineal massage reduces the likelihood of perineal trauma (mainly episiotomies) for primips and the reporting of ongoing perineal pain for multips. Women should be made aware of the likely benefit of perineal massage and provided with information on how to massage. (Cochrane 2006)

At term1

At term

  • Both US and clinical exam are reasonably sensitive in predicting birthweights greater than 4,000 gm in prolonged pregnancy, but they perform less well at predicting the more clinically relevant weight of greater than 4,500 gm. Evidence from one randomized trial shows that induction of labor based on estimated fetal weight does not improve outcomes for either infant or mother. There also is no evidence that an antepartum diagnosis of birthweight greater than 4,000 grams improves outcomes. (USPSTF March 2006)

  • Women who have an uncomplicated singleton breech pregnancy at 36 wks gestation should be offered external cephalic version (ECV). (A-UK)

At term2

At Term

  • Sweeping of the membranes should be offered at term to reduce the need for labor induction (NNT=8). (A-US)

  • Routine sweeping of the membranes at 38 weeks is associated with reduced duration of pregnancy, reduced frequency of pregnancy continuing beyond 41 weeks, and increased discomfort. Number needed to prevent one induction = 8. (Cochrane does not recommend)

Post dates


  • Labor induction is recommended at 41 weeks' to reduce perinatal mortality rates. Induction does not increase rates of perinatal complications, but does not reduce rates of cesarean delivery. (A-UK/US)

  • Prior to formal induction of labour, women should be offered a vaginal examination for membrane sweeping. (A-UK)



  • GDM screening

  • US vs. certain LMP for EDC

  • Abstinence from alcohol during pregnancy

  • Routine GBS screening

  • Routine testing for glycosuria and proteinuria

  • Membrane sweeping at term



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Royal College of Obstetricians and Gynecologists. "Preventing Group B streptococcus (GBS) infection in newborn babies: information for you." RCOG 2006.

National Collaborating Centre for Women's and Children's Health. Antenatal care: routine care for the healthy pregnant woman. Accessed online January 17, 2005, at: http://www.rcog.org.uk/resources/Public/Antenatal_Care.pdf.

Mongelli M, Wilcox M, Gardosi J. Estimating the date of confinement: ultrasonographic biometry versus certain menstrual dates. Am J Obstet Gynecol 1996;174(1 pt 1): 278-81.

Neilson JP. Ultrasound for fetal assessment in early pregnancy. Cochrane Database of Systematic Reviews 1998, Issue 4.

Briscoe, D, et al. Management of Pregnancy Beyond 40 Weeks' Gestation. American Family Physician. May 15, 2005.

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Beckmann MM, Garrett AJ. Antenatal perineal massage for reducing perineal trauma. Cochrane Database of Systematic Reviews 2006, Issue 1.

Kramer MS, Kakuma R. Energy and protein intake in pregnancy. Cochrane Database of Systematic Reviews 2003, Issue 4.

Crowley P. Interventions for preventing or improving the outcome of delivery at or beyond term. Cochrane Database of Systematic Reviews 1997, Issue 1.

Scott D A, Loveman E, McIntyre L, Waugh N. Screening for gestational diabetes: a systematic review and economic evaluation. Health Technology Assessment. 2002;6(11):1-172.

Gilson, GJ, et al. “Prevention of group B streptococcus early-onset neonatal sepsis: comparison of the Center for Disease Control and prevention screening-based protocol to a risk-based protocol in infants at greater than 37 weeks' gestation.” J Perinatol. 2000 Dec;20(8 Pt 1):491-5.

American Diabetes Association (ADA). Standards of medical care in diabetes. III. Detection and diagnosis of GDM. Diabetes Care 2006 Jan

Centers for Disease Control and Prevention. Prevention of perinatal group B streptococcal disease: revised guidelines from CDC. MMWR Recomm Rep 2002 Aug 16;51(RR-11):1-22.

National Collaborating Centre for Women's and Children's Health. Antenatal care: routine care for the healthy pregnant woman. London: RCOG Press; 2003 Oct. 286 p.

Alto, William, MD. No Need for routine glycosuria/proteinuria screen in pregnant women. Journal of Family Practice. Vol 54, No 11, November 2005

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