EvidenceBased Prenatal Care

1
Evidence-Based Prenatal Care

• Carolyn Halley, MD
• August 2006

2
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?
  

3
Providers

• 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)

4
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)

5
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.

6
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)

7
Routine MonitoringUrine 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.

8
Routine MonitoringUrine 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.

9
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)
  

10
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)

11
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)
  

12
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)

13
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)

14
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.

15
Vitamins

• 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)
  

16
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 at increased risk should be screened for
  chlamydial infection. (B-US)
  

17
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)

18
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.

19
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
  

20
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.
  

21
CDMR

• 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)

22
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)

23
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)
  

24
At Term

• Sweeping of the membranes should be offered at
  term to reduce the need for labor induction
  (NNT8). (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)

25
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)

26
Controversies

• 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

27
References

• Villar J, Carroli G, Khan-Neelofur D, Piaggio G,
  Gülmezoglu M. Patterns of routine antenatal care
  for low-risk pregnancy. Cochrane Database of
  Systematic Reviews 2001, Issue 4.
• Royal College of Obstetricians and Gynecologists.
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  2006.
• National Collaborating Centre for Women's and
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• Neilson JP. Ultrasound for fetal assessment in
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• Neilson JP. Ultrasound for fetal assessment in
  early pregnancy. Cochrane Database of Systematic
  Reviews 1998, Issue 4.
  

28
References

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