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--><ref>{{cite paper | author = Urmil Dosajh, Ishita Ghosh, and Rebecka Lundgren | title = Feasibility of Incorporating the Standard Days Method into CASP Family Planning Services in Urban Slums of India | publisher = The Institute for Reproductive Health, Georgetown University | date = September 2005 | pages=p. vi | url = http://pdf.usaid.gov/pdf_docs/PNADG768.pdf | format = PDF | accessdate = 2006-12-2 }}</ref> However, use of NFP in developed countries is rather low. While Catholics made up 24% of the U.S. population in [[2002]],<ref name="adherents">{{cite web | title = Largest Religious Groups in the United States of America | publisher = Adherents.com | date = 2005 | url = http://www.adherents.com/rel_USA.html | accessdate = 2007-03-19 }}</ref> only 1.5% of sexually active Americans avoiding pregnancy were using periodic abstinence.<ref name="cdc">{{cite paper | author = William D. Mosher, Gladys M. Martinez, Anjani Chandra, Joyce C. Abma, and Stephanie J. Willson | title = Use of Contraception and Use of Family Planning Services in the United States: 1982–2002. Advance Data No. 350 | publisher = Center for Disease Control | date = 2002 | url = http://www.cdc.gov/nchs/data/ad/ad350.pdf | format = PDF | accessdate = 2006-09-14 }}</ref>
--><ref>{{cite paper | author = Urmil Dosajh, Ishita Ghosh, and Rebecka Lundgren | title = Feasibility of Incorporating the Standard Days Method into CASP Family Planning Services in Urban Slums of India | publisher = The Institute for Reproductive Health, Georgetown University | date = September 2005 | pages=p. vi | url = http://pdf.usaid.gov/pdf_docs/PNADG768.pdf | format = PDF | accessdate = 2006-12-2 }}</ref> However, use of NFP in developed countries is rather low. While Catholics made up 24% of the U.S. population in [[2002]],<ref name="adherents">{{cite web | title = Largest Religious Groups in the United States of America | publisher = Adherents.com | date = 2005 | url = http://www.adherents.com/rel_USA.html | accessdate = 2007-03-19 }}</ref> only 1.5% of sexually active Americans avoiding pregnancy were using periodic abstinence.<ref name="cdc">{{cite paper | author = William D. Mosher, Gladys M. Martinez, Anjani Chandra, Joyce C. Abma, and Stephanie J. Willson | title = Use of Contraception and Use of Family Planning Services in the United States: 1982–2002. Advance Data No. 350 | publisher = Center for Disease Control | date = 2002 | url = http://www.cdc.gov/nchs/data/ad/ad350.pdf | format = PDF | accessdate = 2006-09-14 }}</ref>


Use of NFP may not be restricted to Catholic couples. In 2002 Sam and Bethany Torode, a then-Protestant Christian couple, published a book advocating NFP use.<!--
Use of NFP may not be restricted to Catholic couples. In 2002, Sam and Bethany Torode, then a [[Protestant Christian]] couple, published a book advocating NFP use.<!--
--><ref>{{cite book |author=Sam Torode, Bethany Torode, J. Budziszewski |title=Open Embrace: A Protestant Couple Rethinks Contraception |publisher=Wm. B. Eerdmans Publishing Company |location=Grand Rapids, Michigan |year=March 2002 |isbn=0-8028-3973-8 }}</ref> (The Torodes have now reversed their NFP-only theological position, and converted to Orthodox Christianity.)<!--
--><ref>{{cite book |author=Sam Torode, Bethany Torode, J. Budziszewski |title=Open Embrace: A Protestant Couple Rethinks Contraception |publisher=Wm. B. Eerdmans Publishing Company |location=Grand Rapids, Michigan |year=March 2002 |isbn=0-8028-3973-8 }}</ref> Five years after authoring the book, the Torodes reversed their advocacy of strict NFP, stating that they found the use of abstinence as their sole form of birth control to be impractical and emotionally damaging. The Torodes [[religious conversion|converted]] to Orthodox Christianity.<!--
--><ref name="openembrace">{{cite web | last = Torode | first = Bethany | title = AN UPDATE FROM BETHANY | date = 2006 | url = http://www.openembrace.com/ | accessdate = 2007-03-13 }}</ref>
--><ref name="openembrace">{{cite web | last = Torode | first = Bethany | title = AN UPDATE FROM BETHANY | date = 2006 | url = http://www.openembrace.com/ | accessdate = 2007-03-13 }}</ref>


Revision as of 21:38, 31 March 2007

Natural family planning
Background
Typenatural birth control
First use1950s (mucus)
mid-1930s (BBT)
1930 (Rhythm)
Ancient (LAM)
Failure rates (first year)
Perfect use1-9%
Typical use3-25%
Usage
ReversibilityYes
User remindersDependent upon strict user adherence to methodology
Clinic reviewNone
Advantages and disadvantages
STI protectionNo
Period advantagesPrediction
BenefitsIn accord with Catholic teachings, no drug effects, can aid pregnancy achievement
This article is about religiously-motivated methods of family planning. For a more general use of the term, see fertility awareness.

Natural family planning (NFP) is a term referring to the family planning methods approved by the Roman Catholic Church. In accordance with the requirements for sexual behavior maintained by this church, NFP excludes the use of birth control, as well as all orgasmic acts outside of those achieved through unprotected vaginal intercourse with the user's spouse.

Periodic abstinence and the natural infertility caused by breastfeeding are the only methods permitted for avoiding pregnancy. Sex during infertile periods is permitted, whether during infertile periods of the menstrual cycle, during pregnancy, or post-menopause. Several methods may be used to identify whether a woman is likely to be fertile, which allows the NFP user and her husband to either try to avoid or to achieve pregnancy.

Prevalence

It is estimated that 2-3% of the world's reproductive age population relies on periodic abstinence to avoid pregnancy.[1] Breastfeeding is believed to reduce the world's fertility rate by 30-45%.[2] However, what portion of this population should be considered NFP users is unclear. Some Catholic sources consider couples that violate the religious restrictions associated with natural family planning to not be NFP users.[3]

Use of natural family planning may be high in Catholic countries: in Brazil, NFP is the third most popular family planning method.[4] Identification of fertile days to avoid pregnancy may be common in developing countries in general - the "safe period" is the most common family planning method in India.[5] However, use of NFP in developed countries is rather low. While Catholics made up 24% of the U.S. population in 2002,[6] only 1.5% of sexually active Americans avoiding pregnancy were using periodic abstinence.[7]

Use of NFP may not be restricted to Catholic couples. In 2002, Sam and Bethany Torode, then a Protestant Christian couple, published a book advocating NFP use.[8] Five years after authoring the book, the Torodes reversed their advocacy of strict NFP, stating that they found the use of abstinence as their sole form of birth control to be impractical and emotionally damaging. The Torodes converted to Orthodox Christianity.[9]

Methods

There are three main types of NFP. These are the observational methods, the statistical or "calendar" methods, and the Lactational Amenorrhea Method. Observational methods rely on biological signs of fertility, while statistical methods approximate the likelihood of fertility, based on the length of past menstrual cycles.

Observational

Some methods of NFP track biological signs of fertility. When used outside of the Catholic concept of NFP, these methods are often referred to simply as fertility awareness methods rather than NFP. The three primary signs of a woman's fertility are her basal body temperature, her cervical mucus, and her cervical position. Two well-known methods of NFP are the Billings ovulation method and the Creighton Model, which use cervical mucus as the primary indicator. If two or more signs are tracked, the method is referred to as the symptothermal method.

Statistical

These methods make statistical estimates as to when a woman is fertile. They include the Rhythm Method and the Standard Days Method.

Lactational amenorrhea

The Lactational Amenorrhea Method (LAM) is a method of avoiding pregnancies which is based on the natural postpartum infertility that occurs when a woman is amenorrheic and fully breastfeeding. The rules of the method help a women identify and possibly length her infertile period. A strict version of LAM is known as ecological breastfeeding.

Effectiveness

The Rhythm Method, the most well known method of NFP, has a perfect-use failure rate of 9% per year, while observational and lactational methods of NFP have lower perfect-use failure rates — between 1%-3% per year. The common usage failure rate is up to 25% per year.[10][11]

Theology

Main article: Christian views on contraception § Roman Catholic Church

Official Catholic

Catholic doctrine holds that God created sexual intercourse to be both unitive and procreative.[12] This church considers deliberately altering fertility or the marital act with the intention of preventing procreation to be sinful. Thus, artificial birth control methods and orgasmic acts outside of full marital intercourse are forbidden, while not having sex at all (abstinence) is considered morally acceptable. [13] While deliberate orgasmic acts outside of full marital intercourse are forbidden, the Church does not condemn foreplay in the context of sexual relations within marriage. Foreplay is permitted as long as the act culminates with the husband penetrating his wife's vagina with his penis and ejaculating while penetrating. [14] However, the Catholic Church does not condemn accidental premature ejaculation.

However, having sex at an infertile time in a woman's life (such as pregnancy or post-menopause) is also considered acceptable, since the infertile condition is considered to be created by God, rather than as an act by the couple.[15]

This church considers it morally acceptable to abstain during the fertile part of the woman's menstrual cycle.[16] Increasing the postpartum infertile period through particular breastfeeding practices — the Lactational Amenorrhea Method — is also considered a moral way to space a family's children.[17]

The Catholic Church acknowledges a potential benefit of spacing children[18] and use of NFP for this reason is encouraged. Humanae Vitae cites "physical, economic, psychological and social conditions" as possibly compelling reasons to avoid pregnancy.[19] Couples are warned, however, against using NFP for selfish, immoral, or insincere reasons.[18] Many Catholic sources extol the benefits children bring to their parents, their siblings, and society in general, and couples are encouraged to have as many children as their circumstances make practical.[20]

Dissident and other opposing

See also: Christian views on contraception § Natural Family Planning only or "artificial" methods too?

Many Catholics have voiced significant disagreement with the Church's stance on contraception.[21] The Canadian Conference of Catholic Bishops issued probably the most heavily dissenting document, the Winnipeg Statement. In it, the bishops argued that many Catholics found it very difficult, if not sometimes impossible, to obey Humanae Vitae. Additionally, they reasserted the Catholic principle of primacy of conscience.[22] Catholics such as Fr. Charles Curran have also criticized the stance of Vitae on artificial birth control.[23]

Theological opposition has additionally come from Protestant Christianity. John Piper's Desiring God ministry states of NFP, "There is no reason to conclude that natural family planning is appropriate but that "artificial" means are not."[24] Sam and Bethany Torode, former advocates of NFP-only, have redacted their position to include barrier methods and explain their current theology this way:

We also see honest congruity with the language of the body by saying "no" to conception with our bodies (via barrier methods or sensual massage) when our minds and hearts are also saying "no" to conception. We don’t believe this angers God, nor that it leads to the slippery slope of relativism or divorce. We strongly disagree with the idea that this is a mortal sin.... it’s a theological attack on women to always require that abstinence during the time of the wife’s peak sexual desire (ovulation) for the entire duration of her fertile life, except for the handful of times when she conceives.[9]

Potential advantages

Fertility awareness methods of NFP can be used to track reproductive health in general, and aid in the diagnosis of gynecological health and/or fertility problems. Particularly with the Sympto-Thermal Method, which is based on a scientific method of self-observation, temperature, external and internal mucus, and cervical observations are all recorded daily on a calendar. Any observation of irregularities may prove helpful, providing a doctor or gynecolotist with important diagnostic information with dates and a personal history of any abnormalities.[25] The fertility knowledge gained from NFP methods may also be used to help achieve pregnancy.[26]

Since NFP methods do not interfere with natural female hormone cycles, NFP is not proven to have any physical side effects. Relatedly, intercourse may be spontaneous, as compared to the use of condoms.[27] However, intercourse is not spontaneous during the days where sex is forbidden.

NFP can be free or very low-cost.[26] Some methods encourage the use of a thermometer and/or photocopied charts, which can be obtained relatively inexpensively. Some couples choose to use software or to use other devices such as a string of beads for counting the days.

Divorce rate

NFP increases marital satisfaction and helps lower divorce rates. One study involving 505 women using NFP found a correlation between lower divorce rates and the use of NFP. [28]

Claims regarding communication

Fertility awareness forms of NFP (which require daily charting of fertility signs) can result in couples communicating more about their bodies and sexuality; this is said to improve communication skills throughout the entire marriage. One idea, called a "courtship and honeymoon effect",[29] is that the scheduled abstinence encourages couples to express love in non-genital ways, and to have a greater appreciation for intercourse when it does happen.[30] To date there has been no study exploring this idea.

Potential disadvantages

Abstinence requirement

Users may find that the abstinence required by the Catholic Church is beyond their capabilities or wishes. The fertility awareness and statistical forms of NFP require periodic abstinence, known as continence, most commonly 8-10 days of each menstrual cycle. It is common for the woman's sexual desire to be highest on those fertile days, and lower in other parts of the cycle.[31] That the couple must abstain from sex during the woman's periods of peak sexual desire may be deeply frustrating for both partners, and lead to feelings of isolation.[32]

A prominent example of a person who holds this view is Bethany Torode. She and her husband co-authored a book titled Open Embrace, which promoted exclusive use of abstinence-based NFP in the context of their Christian faith. Five years later, Torode described significant drawbacks associated with the abstinence requirement of NFP:

"Our personal experience in the past five years has shown that we had a lot to learn about NFP, and that there is a dark side we weren’t aware of. Though Open Embrace said that it only involves a short period of abstinence, we didn’t know that during breastfeeding cycles it often involves month-long periods of abstinence and dehabilitating stress. During such times (as well as during menopause and stressful life seasons), strict NFP reaches a point where it is more harmful for a marriage than good."[9]
"We also see honest congruity with the language of the body by saying "no" to conception with our bodies (via barrier methods or sensual massage) when our minds and hearts are also saying "no" to conception. We don’t believe this angers God, nor that it leads to the slippery slope of relativism or divorce. We strongly disagree with the idea that this is a mortal sin." [9]
"... it’s a theological attack on women to always require that abstinence during the time of the wife’s peak sexual desire (ovulation) for the entire duration of her fertile life, except for the handful of times when she conceives." [9]

Few Catholics in the United States use periodic abstinence as birth control. While Catholics made up 24% of the U.S. population in 2002,[6] only 1.5% of sexually active Americans avoiding pregnancy were using periodic abstinence/NFP.[7]

Other reported disadvantages of the abstinence requirement are:

  • Some methods of NFP require up to six months of research and observation (and abstinence) in order to collect baseline data, so these methods cannot be immediately implemented by a new user. [33]
  • Couples seeking the lowest risk of pregnancy (less than 1% per year) may be required to abstain for more than half of each menstrual cycle.
  • For women in certain situations - breastfeeding, perimenopause, or with hormonal diseases such as PCOS - abstinence may be required for months at a time.[9]
  • When taught in the context of Catholicism, NFP teaches that orgasmic acts outside of intercourse, such as oral sex and masturbation, are incompatible with the correct practice of NFP. Some couples are not comfortable with this restriction. Periodic abstinence also limits spontaneous sex.[34]

Method limitations

  • Some fertility awareness forms of NFP require observation or touching of cervical mucus, an activity with which some women are not comfortable. Some practitioners prefer to use the term "cervical fluid" to refer to cervical mucus, in an attempt to make the subject more palatable to these women. Some drugs, such as decongestants, can change cervical mucus. Women may not be able to rely on these forms of NFP while taking these drugs.[35]
  • Some fertility awareness forms require tracking of basal body temperatures. Because irregular sleep can interfere with the accuracy of basal body temperatures, shift workers and those with very young children, for example, might not be able to rely on those methods.[35]
  • The NFP methods that encourage breastfeeding infertility can only be used until the woman's first post-partum menstruation. Even the most strict form results in average return of menses at 14 months post-partum,[36][37] and menstruation can return as early as 6 weeks post-partum.[38]

Implantation failure and miscarriage

  • It has been suggested that unprotected intercourse in the infertile periods of the menstrual cycle may still result in conceptions, but create embryos incapable of implanting.[39]

It has also been suggested that pregnancies resulting from method failures of NFP are at increased risk of miscarriage and birth defects due to aged gametes at the time of conception.[40] The most recent research, however, suggests timing of conception has no effect on miscarriage rates,[41] low birth weight, or preterm delivery.[42]

See also

NFP information

Critical perspectives

  • openembrace.com - An update from Sam & Bethany Torode, authors of Open Embrace, which details how they have changed many of their views since authoring their book.

Footnotes

  1. ^ Che Y, Cleland J, Ali M (2004). "Periodic abstinence in developing countries: an assessment of failure rates and consequences". Contraception. 69 (1): 15–21. PMID 14720614.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Kippley, John (1996). The Art of Natural Family Planning (4th Edition ed.). Cincinnati, OH: The Couple to Couple League. pp. p. 145. ISBN 0-926412-13-2. {{cite book}}: |edition= has extra text (help); |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Kippley (1996), p. 13
    "Question #8". FREQUENTLY ASKED QUESTIONS. Serena Canada. 2006. Retrieved 2007-03-19.
  4. ^ Keller S (1996). "Traditional beliefs part of people's lives". Network. 17 (1): 10–1. PMID 12320441.
  5. ^ Urmil Dosajh, Ishita Ghosh, and Rebecka Lundgren (September 2005). "Feasibility of Incorporating the Standard Days Method into CASP Family Planning Services in Urban Slums of India" (PDF). The Institute for Reproductive Health, Georgetown University: p. vi. Retrieved 2006-12-2. {{cite journal}}: |pages= has extra text (help); Check date values in: |accessdate= (help); Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link)
  6. ^ a b "Largest Religious Groups in the United States of America". Adherents.com. 2005. Retrieved 2007-03-19. Cite error: The named reference "adherents" was defined multiple times with different content (see the help page).
  7. ^ a b William D. Mosher, Gladys M. Martinez, Anjani Chandra, Joyce C. Abma, and Stephanie J. Willson (2002). "Use of Contraception and Use of Family Planning Services in the United States: 1982–2002. Advance Data No. 350" (PDF). Center for Disease Control. Retrieved 2006-09-14. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link) Cite error: The named reference "cdc" was defined multiple times with different content (see the help page).
  8. ^ Sam Torode, Bethany Torode, J. Budziszewski (March 2002). Open Embrace: A Protestant Couple Rethinks Contraception. Grand Rapids, Michigan: Wm. B. Eerdmans Publishing Company. ISBN 0-8028-3973-8.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
  9. ^ a b c d e f Torode, Bethany (2006). "AN UPDATE FROM BETHANY". Retrieved 2007-03-13. Cite error: The named reference "openembrace" was defined multiple times with different content (see the help page).
  10. ^ "Facts in Brief: Contraceptive Use". Guttmacher Institute. 2005. Retrieved 2006-06-19. {{cite web}}: Unknown parameter |month= ignored (help)
  11. ^ Frank-Herrmann P, Freundl G, Baur S; et al. (December 1991). "Effectiveness and acceptability of the sympto-thermal method of natural family planning in Germany". American journal of obstetrics and gynecology. 165 (6 Pt 2): 2052–2054. PMID 1755469. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
    Clubb EM, Pyper CM, Knight J (1991). "A pilot study on teaching natural family planning (NFP) in general practice". Proceedings of the Conference at Georgetown University, Washington, DC. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)CS1 maint: multiple names: authors list (link)
    "European Natural Family Planning Study Groups. Prospective European multi-center study of natural family planning (1989-1992): interim results". Advances in Contraception. 9 (4): 269–283. December 1993. PMID 8147240.{{cite journal}}: CS1 maint: year (link)
    Frank-Herrmann P, Freundl G, Gnoth C; et al. (June–September 1997). "Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behavior: a German prospective long-term study". Advances in Contraception. 13 (2–3): 179–189. PMID 9288336. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: date format (link) CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
  12. ^ "#2363". Catechism of the Catholic Church, Second Edition. United States Catholic Conference. 2000. pp. Article 6: The Sixth Commandment. Retrieved 2006-06-15.
  13. ^ CCC #2351-2359
  14. ^ Christopher West (2000). Good News about Sex and Marriage: Answers to Your Honest Questions about Catholic Teaching. Servant Publications. pp. 88–91.
  15. ^ "Casti Connubii". Encyclical of Pope Pius XI. United States Catholic Conference. 1930. pp. Section 59. Retrieved 2006-06-15.
  16. ^ CCC #2370
  17. ^ "NFP - Two basic forms". Couple to Couple League. Retrieved 2006-06-24.
  18. ^ a b CCC #2368
  19. ^ "Humane Vitae". Encyclical of Pope Paul VI. The Holy See. July 25, 1968. pp. Section I.10. Retrieved 2006-06-15.
  20. ^ Humanae Vitae Section I.9
    "The Blessings of Children". One More Soul. Retrieved 2006-06-24.
    "In Praise of Big Families". CatholicExchange.com. Retrieved 2006-06-24.
    "Principles of the Couple to Couple League". Couple to Couple League International. Retrieved 2006-06-24.
  21. ^ A summary and restatement of the debate is available in Roderick Hindery. "The Evolution of Freedom as Catholicity in Catholic Ethics." Anxiety, Guilt, and Freedom. Eds. Benjamin Hubbard and Brad Starr, UPA, 1990.
  22. ^ "Canadian Bishops' Statement on the Encyclical "Humanae Vitae"". Retrieved 2006-10-02.
  23. ^ Charles E. Curran,. Loyal Dissent: Memoir of a Catholic Theologian (Moral Traditions). Washington, D.C: Georgetown University Press. ISBN 1-58901-087-6.{{cite book}}: CS1 maint: extra punctuation (link)
  24. ^ Desiring God Staff (2006). "Does the Bible permit birth control?" (html). Questions and Answers. Desiring God. Retrieved 2006-10-27.
  25. ^ Cimperman, Sarah (2005). "Fertility Awareness for Reproductive Health". Santé! Holistic Health News from Dr. Sarah Cimperman Newsletter. Retrieved 2006-06-15. {{cite web}}: Unknown parameter |month= ignored (help)
  26. ^ a b "Basic Information on Natural Family Planning". Natural Family Planning. United States Conference of Catholic Bishops. Retrieved 2006-06-15.
  27. ^ "Condoms and HIV Prevention". The Body: The Complete HIV/AIDS Resource. December 2001. Retrieved 2006-06-24.{{cite web}}: CS1 maint: year (link)
  28. ^ Divorce Rate Comparisons Between Couples Using Natural Family Planning & Artificial Birth Control
  29. ^ Kippley (1996), p. 246
    Weschler, Toni (2002). Taking Charge of Your Fertility (Revised Edition ed.). New York: HarperCollins. pp. p. 123. ISBN 0-06-093764-5. {{cite book}}: |edition= has extra text (help); |pages= has extra text (help)
  30. ^ Shivanandan, Mary (1999). "NFP & the Couple's Relationship". Diocesan Development Program for Natural Family Planning. Retrieved 2006-06-15. {{cite web}}: Text "work Diocesan Development Program for Natural Family Planning" ignored (help)
  31. ^ Susan B. Bullivant, Sarah A. Sellergren, Kathleen Stern; et al. (February 2004). "Women's sexual experience during the menstrual cycle: identification of the sexual phase by noninvasive measurement of luteinizing hormone". Journal of Sex Research. 41 (1): 82-93 (in online article, see pp.14-15, 18-22). PMID 15216427. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
  32. ^ http://www.openembrace.com/
  33. ^ "Safer Sex and Contraception - Natural Family Planning". Family Planning Victoria. 2005. Retrieved 2006-07-06.
  34. ^ a b "Natural family planning". University of Iowa Health Care Website. McKesson Health Solutions. 2003. Retrieved 2006-06-15.
  35. ^ a b "How to Observe and Record Your Fertility Signs". Fertility Friend Handbook. Tamtris Web Services. 2004. Retrieved 2005-06-15.
  36. ^ Sheila K. and John F. Kippley (November–December 1972). "The relation between breastfeeding and amenorrhea". Journal of obstetric, gynecologic, and neonatal nursing. 1 (4): 15–21. PMID 4485271.{{cite journal}}: CS1 maint: date format (link) CS1 maint: year (link)
  37. ^ Sheila Kippley (November–December 1986). "Breastfeeding survey results similar to 1971 study". The CCL News. 13 (3): 10.{{cite journal}}: CS1 maint: date format (link) CS1 maint: year (link) and 13:4 (January-February 1987) 5.
  38. ^ "Postpartum Visit Checklist". StorkNet.com. Retrieved 2006-06-24.
  39. ^ Luc Bovens (2006). "The rhythm method and embryonic death" (PDF). Journal of Medical Ethics. 32: 355–356. {{cite journal}}: External link in |journal= (help)
  40. ^ Gray, RH (October 1984). "Aged gametes, adverse pregnancy outcomes and natural family planning. An epidemiologic review". Contraception. 30 (4): 297–309. PMID 6509983.{{cite journal}}: CS1 maint: year (link)
  41. ^ Gray RH, Simpson JL, Kambic RT (May 1995). "Timing of conception and the risk of spontaneous abortion among pregnancies occurring during the use of natural family planning". American Journal of Obstetrics and Gynecology. 172 (5): 1567–1572. PMID 7755073.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
  42. ^ Barbato M, Bitto A, Gray RH; et al. (June–September 1997). "Effects of timing of conception on birth weight and preterm delivery of natural family planning users". Advances in Contraception. 13 (2–3): 215–228. PMID 9288339. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: date format (link) CS1 maint: multiple names: authors list (link) CS1 maint: year (link)
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