Breastfeeding and Fertility

By Kelly Bonyata, BS, IBCLC

How can I use breastfeeding to prevent pregnancy?

The Exclusive Breastfeeding method of birth control is also called the Lactational Amenorrhea Method of birth control, or LAM. Lactational amenorrhea refers to the natural postpartum infertility that occurs when a woman is not menstruating due to breastfeeding. Many mothers receive conflicting information on the subject of breastfeeding and fertility.

Myth #1 – Breastfeeding cannot be relied upon to prevent pregnancy.

Myth #2 – Any amount of breastfeeding will prevent pregnancy, regardless of the frequency of breastfeeding or whether mom’s period has returned.

Exclusive breastfeeding has in fact been shown to be an excellent form of birth control, but there are certain criteria that must be met for breastfeeding to be used effectively.

Exclusive breastfeeding (by itself) is 98-99.5% effective in preventing pregnancy as long as all of the following conditions are met:

  1. Your baby is less than six months old
  2. Your menstrual periods have not yet returned
  3. Baby is breastfeeding on cue (both day & night), and gets nothing but breastmilk or only token amounts of other foods.
Effectiveness of Birth Control Methods
Number of Pregnancies per 100 Women
Method Perfect Use Typical Use
LAM 0.5 2.0
Mirena® IUD 0.1 0.1
Depo-Provera® 0.3 3.0
The Pill / POPs 0.3 8.0
Male condom 2.0 15.0
Diaphragm 6.0 16.0
* Adapted from information at

How can I maximize my natural period of infertility?

Timing for the return to fertility varies greatly from woman to woman and depends upon baby’s nursing pattern and how sensitive mom’s body is to the hormones involved in lactation.

  • Breastfeeding frequency and total amount of time spent breastfeeding per 24 hours are the strongest factors leading to the return of fertility: a mother is more likely to see the return of fertility if baby’s nursing frequency and/or duration is reduced, particularly if the change is abrupt.
  • In some populations, research has shown that night nursing slows the return to fertility.
  • One study showed that mothers who were separated from their infants (but expressed milk to provide 100% breastmilk for baby) had a higher pregnancy risk (5.2%) during the first 6 months (Valdes 2000).
  • The introduction of solid food can also be a factor in the return of fertility. Once baby starts solids (if mom’s cycles have not returned), the natural period of infertility may be prolonged by breastfeeding before offering solids, starting solids gradually, and not restricting nursing.

You can achieve higher effectiveness by practicing ecological breastfeeding:

  • keeping baby close
  • breastfeeding on cue (day and night)
  • using breastfeeding to comfort your baby
  • breastfeeding in a lying-down position for naps and at night
  • using no bottles or pacifiers

If you practice ecological breastfeeding:

  • Chance of pregnancy is practically zero during the first three months, less than 2% between 3 and 6 months, and about 6% after 6 months (assuming mom’s menstrual periods have not yet returned).
  • The average time for the return of menstrual periods is 14.6 months.
  • Moms whose cycles return early tend to be infertile for the first few cycles. Moms whose cycles return later are more likely to ovulate before their first period.
    Source: Natural Child Spacing and Breastfeeding by Jen O’Quinn

Source: Natural Child Spacing and Breastfeeding by Jen O’Quinn

While it is possible for a nursing mom to become pregnant while she is breastfeeding and before she has her first menstrual period, it is rare. Most moms do not get pregnant until after their first period (often referred to as the “warning period”). Even after that, while some can become pregnant the first cycle, others will require months of cycles before pregnancy can occur. Still others (this is quite uncommon) may not be able to become pregnant until complete weaning has occurred.

The transition to full fertility

Several studies have indicated that fertility and ovarian activity return step by step (Ellison 1996, p. 326-327):

  1. Follicular activity without ovulation (No chance of pregnancy.)
    1a. Menstruation without ovulation (This does not always occur–see below.)
  2. Ovulation without luteal competence (After the egg is released, fertilization may take place. During the luteal phase, the uterine lining is prepared for implantation as the egg travels down the fallopian tube and into the uterus. If the uterine lining is not adequately prepared for implantation, the implantation will probably not be successful.)
  3. Full luteal competence (Full fertility — at this point breastfeeding no longer has any effect on your chance of pregnancy.)

It is possible to have one or (occasionally) more periods before you start ovulating. In this case, menstruation begins during the first stage of the return to fertility –before ovulation returns. Cycles without ovulation are most common during the first six months postpartum. For other mothers, the first menstruation is preceded by ovulation – a longer period of lactational amenorrhea increases the likelihood that you will ovulate before that first period.

A very small percentage of women will become pregnant during their first postpartum ovulation, without having had a postpartum period. Per fertility researcher Alan S. McNeilly, this “is rare and in our experience is related to a rapid reduction in suckling input.”

It is not uncommon for breastfeeding mothers to report cyclical cramping or PMS-type symptoms – symptoms of an oncoming period without the period – for weeks or even months before their period returns. When this happens, the body is probably “gearing up” for the return of menstruation, but breastfeeding is still delaying the return of fertility.

The amount of time that it takes for the transition to full fertility varies from woman to woman. In general, the earlier that your menses return, the more gradual the return to full fertility.

Reference Menstruation without ovulation First ovulation without luteal competence Time between 1st period and ovulation
0-6 mo after 6 mo 0-6 mo after 6 mo
Eslami 1990 67% 22% 8.4 weeks 0.1 week
Gray 1990 45.1% “the rate fell greatly” 41%

Reference Frequency of ovulation
1st cycle
2nd cycle
1st cycle
2nd cycle
Formula-feeding only:
2nd cycle
Howie 1982 45% 66% 70% 84% 94%

Do I need to wean to get pregnant?

Probably not. If you are still transitioning to full fertility (as discussed above), breastfeeding may affect the success of implantation. Once implantation is successful, breastfeeding should not affect a healthy pregnancy (see A New Look at the Safety of Breastfeeding During Pregnancy for more information). If your periods have come back and settled into a regular pattern, it is likely that breastfeeding is no longer affecting your fertility.

Many moms can conceive without deliberately changing their toddler’s nursing patterns. There is no “magic” threshold of breastfeeding that will allow you to conceive — every mother is different. Some moms need to stretch out nursing frequency and/or shorten nursing sessions to make it easier to conceive — babies naturally do this themselves as they get older, so one of your options is simply to wait a bit.

Changes that are more abrupt tend to bring fertility back faster (e.g., cutting out one nursing session abruptly, rather than gradually decreasing nursing time at that session) —even if you continue to breastfeed a great deal— this is why many mothers experience the return of fertility when their child sleeps through the night or starts solid foods. If you decide to make changes to your nursing pattern, the time of day that you make the change (e.g., cutting out or shortening a nighttime nursing session as opposed to a daytime nursing session) should not make that much of a difference. Current research indicates that nursing frequency and total amount of time at the breast per 24 hours are the most important factors, rather than the time of day that the suckling occurs.

A few moms do find it impossible to conceive while nursing, but this is not at all common.

Many mothers wonder whether breastfeeding will affect the reliability of pregnancy tests. It does not — pregnancy tests measure the amount of the hormone hCG (human chorionic gonadotropin) in blood or urine, and hCG levels are not affected by breastfeeding. The developing placenta begins releasing hCG upon implantation; a pregnancy can generally be detected with a pregnancy test within 7-14 days after implantation.

For more information, see Getting Pregnant While Breastfeeding by Hilary Flower.

When you do get pregnant while breastfeeding, what next? See Nursing During Pregnancy & Tandem Nursing for more information.


References and Additional Resources

Fertility and conceiving while breastfeeding

Birth Control and Breastfeeding @

Getting Pregnant While Breastfeeding by Hilary Flower

Menstruation and Breastfeeding by Becky Flora, IBCLC

Breastfeeding and Menstruation, Birth Control and Vaginal Dryness by Paula Yount

Can I get pregnant while I am breastfeeding? LLL FAQ

The Garden of Fertility by Katie Singer

Breastfeeding and Birth Control by Anne Smith, IBCLC

Breastfeeding and Fertility by Sherri Hedberg, IBCLC

Toddler Tips: Fertility and Night Nursing from NEW BEGINNINGS, Vol. 18, No. 1, January-February 2001 pp. 23-25

Taking Charge of Your Fertility website – check out the library and the discussion boards.

Campino C, Torres C, Rioseco A, Poblete A, Pugin E, Valdes V, Catalan S,
Belmar C, Seron-Ferre M. Plasma prolactin/oestradiol ratio at 38 weeks gestation predicts the duration of lactational amenorrhoea. Hum Reprod. 2001 Dec;16(12):2540-5. “At 38 weeks gestation, the ratio PRL/oestradiol identified all individual women according to the subsequent duration of their lactational amenorrhoea, suggesting that duration of lactational amenorrhoea is conditioned during pregnancy.”

Ellison, PT. Breastfeeding, Fertility, and Maternal Condition. In: Stuart-Macadam P, Dettwyler KA, ed. Breastfeeding: Biocultural Perspectives. Hawthorne, NY: Aldine de Gruyter, 1995:305-345.

Eslami SS, Gray RH, Apelo R, Ramos R. The reliability of menses to indicate the return of ovulation in breastfeeding women in Manila, The Philippines. Stud Fam Plann. 1990 Sep-Oct;21(5):243-50.

Gray RH, Campbell OM, Apelo R, Eslami SS, Zacur H, Ramos RM, Gehret JC, Labbok MH. Risk of ovulation during lactation. Lancet. 1990 Jan 6;335(8680):25-9.

Howie PW, McNeilly AS, Houston MJ, Cook A, Boyle H. Fertility after childbirth: infant feeding patterns, basal PRL levels and post-partum ovulation. Clin Endocrinol (Oxf). 1982 Oct;17(4):315-22.

Several papers and discussions on fertility and breastfeeding from The United Nations University Press Food and Nutrition Bulletin Volume 17, Number 4, December 1996.

 Exclusive breastfeeding/Lactational Amenorrhea Method of birth control

What is the contraceptive effect of breastfeeding my baby? from the Managing Contraception website

The Garden of Fertility by Katie Singer

Breastfeeding and Childspacing by Dr. William Sears

What is LAM?. Did you know that exclusive breastfeeding can prevent pregnancy for up to six months? This site answers your questions!

Natural Child Spacing and Breastfeeding by Jen O’Quinn, from LEAVEN, Vol. 34 No. 6, December 1998 – January 1999, p. 128.

The Lactational Amenorrhea Method (LAM): Another Choice for Mothers by Miriam H. Labbok, MD, MPH, from Breastfeeding Abstracts, August 1993, Volume 13, Number 1, pp. 3-4.

Fact Sheet on the Lactational Amenorrhea Method (LAM) from the LINKAGES Project (PDF version) Also available in French and Spanish from the LINKAGES website.

Managing Fertility Naturally During Breastfeeding. From the Billings Ovulation Method of Natural Family Planning. Continue on to their home page for more info on the method.

Taylor, H. William, et al. Continuously Recorded Suckling Behaviour and Its Effect on Lactational Amenorrhoea. J Biosoc Sci. 1999;31: 289-310.

Valdes V, Labbok MH, Pugin E, Perez A. The efficacy of the lactational amenorrhea method (LAM) among working women. Contraception. 2000 Nov;62(5):217-9.

Breastfeeding as a means to fertility regulation: reviewing the evidence. Progress in Reproductive Health Research. 2000;55:1-7.

 Print Resources

Your Fertility Signals by Merryl Winstein

Taking Charge of Your Fertility by Toni Weschler

Breastfeeding and Natural Child Spacing by S.K. Kippley

A Pocket Guide to Managing Contraception by Robert Anthony Hatcher, M.D., MPH, et. al. includes accurate information on LAM and other methods of contraception

Ellison, Peter T. “Breastfeeding, Fertility and Maternal Condition,”from Breastfeeding: Biocultural Perspectives (Stuart-Macadam, P. and Dettwyler, K., ed.), New York: Walter de Gruyter, Inc., 1995, p. 305-345.

Mohrbacher, N. and Stock, J. “Breastfeeding, Fertility, and Contraception” from The Breastfeeding Answer Book, Revised ed. Schaumburg, Illinois: La Leche League International, 1997, pp.356-363.

Valdés V, Labbok MH, Pugin E, and Perez A. The efficacy of the lactational amenorrhea method (LAM) among working women. Contraception, 01 Nov 2000; 62(5): 217-9.

KellyMom is sponsored this month by Earth Mama Angel Baby, maker of natural and organic herbal products, who has graciously helped pay our costs this month.
Our sponsor is not responsible for and has had no influence over the creation, selection or presentation of evidence-based or other information or resources provided on this site.