Levonorgestrel use while Breastfeeding

Drugs containing Levonorgestrel: Mirena, Lutera, Plan B, Aviane, Seasonique, Alesse, Orsythia, Plan B One-Step, Levora, Seasonale, Show all 62 »Skyla, Camrese, Portia, Trivora, Tri-Levlen, Jolessa, Triphasil, Lybrel, Nordette, Altavera, Sronyx, Alesse-28, Quasense, Amethia, Climara Pro, Chateal, Enpresse, Kurvelo, Quartette, LoSeasonique, Myzilra, Lessina, Amethyst, Falmina, Levlen, Marlissa, Aubra, Daysee, Trivora-28, Norplant System, Next Choice, Introvale, Next Choice One Dose, Triphasil-28, Amethia Lo, Alesse-21, Preven EC, My Way, Min-Ovral 21, Nordette-28, Levonest, Triquilar 21, CamreseLo, Opcicon One-Step, Fallback Solo, Triphasil-21, Levlite, Nordette-21, Triquilar 28, Min-Ovral 28, Delyla, Setlakin

Levonorgestrel Levels and Effects while Breastfeeding

Summary of Use during Lactation

This record contains information specific to levonorgestrel used alone. Those with an interest in a combination oral contraceptive should consult the record entitled, "Contraceptives, Oral, Combined."

Although nonhormonal methods are preferred during breastfeeding, progestin-only contraceptives such as levonorgestrel are considered the hormonal contraceptives of choice during lactation. Fair quality evidence indicates that levonorgestrel does not adversely affect the composition of milk, the growth and development of the infant or the milk supply.[1][2][3] Some evidence indicates that progestin-only contraceptives may offer protection against bone mineral density loss during lactation, or at least not exacerbate it.[4][5][6]

The levonorgestrel IUD (Myrena) is recommended to be inserted at least 6 weeks postpartum and in some cases up to 12 weeks postpartum when uterine involution is complete. However, the American College of Obstetrics and Gynecology considers earlier insertion to be appropriate based on expert opinion.[7] Two small, randomized studies on this point differed in their outcomes. One found that early insertion did not adversely affect breastfeeding,[8] and the other found that immediate IUD insertion markedly reduced the breastfeeding rate at 6 months postpartum.[9] Based on the available evidence, current expert opinion in the United States holds that the advantages of using progestin-only contraceptive products generally outweigh the theoretical or proven risks before 4 weeks postpartum.[10] However, it may be prudent to avoid administration of these products until lactation is well established. One large European cohort study published since the above recommendations found that breastfeeding at the time of IUD insertion increased the risk of uterine perforation.[11] Another recent randomized trial found that the expulsion rate of the levonorgestrel IUD was unacceptably high in breastfeeding women.[12]

Use of 2 doses of 0.75 mg of levonorgestrel 12 hours apart for postcoital contraception has not been studied, but data from a study on a single 1.5 mg dose indicate that nursing can be resumed 8 hours after a large dose.[13] Resumption of breastfeeding 3 to 4 hours after the dose may be acceptable.[14]

Drug Levels

Levonorgestrel is a synthetic progestin that is the active isomer of the racemate norgestrel. It is considered to be twice as potent on a weight basis as the racemic mixture. Norplant is a subdermal implant that releases levonorgestrel at a rate of about 85 mcg daily initially, dropping to about 50 mcg daily at 9 months. Norplant-2 releases levonorgestrel at a rate of about 50 mcg daily. Neither of the Norplant products are available in the United States at the time of this revision.

Maternal Levels, Oral. Fifteen women who were fully breastfeeding and 8 weeks postpartum were given oral levonorgestrel either alone in a dose of 30 mcg daily or in an estrogen-containing oral contraceptive in a dose of 150 mcg or 250 mcg daily. Five women received each dose for 10 days before breastmilk sample collection. With the 30 mcg dose, the drug was undetectable in all of the women in prenursing milk (<0.05 mcg/L) or postnursing milk (<0.1 mcg/L) at 3 to 23 hours after the dose. With the 150 mcg dose, the highest levels in milk were found 3 hours after the dose with foremilk and hindmilk levels of 0.34 and 0.54 mcg/L, respectively; levels decreased to 0.11 and 0.17 mcg/L, respectively, at 23 hours after the dose. With the 250 mcg dose, the highest levels in milk were found 3 hours after the dose with foremilk and hindmilk levels of 0.51 and 1.05 mcg/L, respectively; levels decreased to 0.22 and 0.38 mcg/L, respectively, at 23 hours after the dose. The authors estimated that fully breastfed infants would receive 0.4 to 0.5 mcg daily in breastmilk, or about 0.1% of the total (not weight-adjusted) maternal dose.[15]

Two women with well-established lactation (exact time postpartum not stated) were given an oral contraceptive containing 150 mcg of levonorgestrel daily. Each had breastmilk levels measured on 2 occasions 10 to 12 hours after a dose between days 6 and 20 of use. The average of their levonorgestrel milk levels was 0.18 mcg/L (range 0.135 to 0.223 mcg/L).[16]

Milk levonorgestrel levels were measured in 4 women after daily ingestion of oral levonorgestrel 50 or 150 mcg started after 3 months postpartum. Peak milk levonorgestrel levels occurred between 1 and 3 hours and were in the ranges of 0.06 to 0.2 mcg/L after the 50 mcg dose and 0.35 to 0.45 mcg/L after the 150 mcg dose. After the 50 mcg dose, milk levels dropped to undetectable (<0.05 mcg/L) by 4 hours after the dose. After the 150 mcg dose, milk levels dropped to about 0.35 mcg/L at 4 hours after the dose and remained there for the next 2 hours.[17]

At 6 to 20 weeks postpartum, 10 women received single tablets containing 30 mcg of levonorgestrel and another 15 women received a single tablet of a combination oral contraceptive containing 250 mcg of levonorgestrel. At 2 to 2.5 hours after the dose, a foremilk sample was taken. The mothers breastfed their infants and then a hindmilk sample was taken. The 2 samples were pooled for assay. After the 30 mcg dose, milk levels averaged 0.05 mcg/L (range 0.03 to 0.076 mcg/L); after the 250 mcg dose, milk levels averaged 0.64 mcg/L (range 0.3 to 1.3 mcg/L).[18]

Twelve breastfeeding women averaging 11.1 weeks postpartum (range 6 and 12 weeks) received a single dose of 1.5 mg of levonorgestrel orally. Blood and milk samples were obtained over the next 72 hours. Peak milk levels of levonorgestrel occurred 3.9 hours after the dose; milk levels fell with a mean half-life in milk of 26 hours. The mean concentration in milk was 1.7 mcg/L during the first day, 0.4 mcg/L the second day and 0.2 mcg/L on the third day after the dose. The authors estimated that a fully breastfed infant would receive 1.6 mcg of levonorgestrel in the first 24 hours, 0.3 mcg in the second 24 hours, and 0.2 mcg in the third 24 hours after the dose.[13]

Maternal Levels, Inplant. One hundred women who received Norplant implants at an average of day 55 postpartum were compared to 100 women receiving a postpartum nonhormonal IUD. Milk levonorgestrel levels were measured at various times after insertion. During days 1 to 4 postinsertion, average milk levels were 0.079 mcg/L (n = 5); during days 9 to 14, average levels were 0.128 mcg/L (n = 22); during days 16 to 22, average levels were 0.163 mcg/L (n = 3); and during days 34 to 40, average levels were 0.116 mcg/L (n = 21). The authors estimated that a fully breastfed infant would receive a levonorgestrel dosage of 15 to 18 ng/kg daily in breastmilk during this time period.[19]

A study compared women who received Norplant-2 (n = 14), an IUD that released 20 mcg levonorgestrel daily (n = 14) or oral tablets containing 30 mcg of levonorgestrel (n = 10) at 4 to 6 weeks postpartum. Pooled fore- and hindmilk samples were measured several times on the first day of drug use and periodically thereafter until day 28. Norplant-2 users had milk levels that reached an average of 0.067 mcg/L by day 2 and maintained those levels throughout the 28 days. IUD users had milk levels that reached an average of 0.046 mcg/L by day 2 and maintained those levels throughout the 28 days. Oral tablet users had 2-hour peak milk levels that averaged 0.05 mcg/L throughout the 28 days.[20]

Maternal Levels, IUD. Ten women had IUDs that released either 10 mg or 30 mcg of levonorgestrel daily placed at 6 weeks postpartum. Milk was analyzed for levonorgestrel at various times over a 12-month period. All milk levels were less than 0.1 mcg/L, regardless of the dose that the mother was receiving.[21]

Infant Levels, Oral. Two 8-week old infants whose mothers were taking a combination oral contraceptive containing 250 mcg of levonorgestrel had plasma levels measured 5 hours after the maternal dose and 2 hours after nursing (i.e., nursed at the time of peak milk level). Plasma levels were 0.058 and 0.115 mcg/L in the 2 infants. A third infant whose mother was taking 30 mcg daily had undetectable (<0.005 mcg/L) in its plasma. The authors concluded that these results indicate that the infants are able to metabolize levonorgestrel and that no accumulation occurs in infant plasma.[15]

At 6 to 20 weeks postpartum, 10 women received single tablets containing 30 mcg of levonorgestrel and another 15 women received a single tablet of a combination oral contraceptive containing 250 mcg of levonorgestrel. At 2 to 2.5 hours after the dose, the mothers breastfed their infants; infant serum samples were taken 1.5 to 2 hours later at about 4 hours after the maternal dose. Infant serum levels after the 30 and 250 mcg doses averaged 0.019 and 0.078 mcg/L, respectively. These levels were 2% and 1%, respectively, of peak maternal serum levels drawn at 2 to 2.5 hours after the dose.[18]

Thirty mothers received 30 mcg oral levonorgestrel tablets daily for 5 weeks. Ten began at 4 weeks postpartum, 10 began at 12 weeks postpartum and 10 began at 24 weeks postpartum. Because of assay and serum sample size limitations, serum samples were obtained from some of the breastfed infants during the first and fifth weeks of maternal therapy as representative of the entire group. Based on infant serum levels, the authors concluded that absorption of the drug was not great until 12 weeks postpartum and metabolism was not well developed until 24 weeks postpartum.[22] The unusual and incomplete blood sampling scheme casts some doubt on the results of this study.

Infant Levels, Implant. Forty-two women received Norplant implants between days 30 and 40 postpartum. The women breastfed for 1 year and donated 1 blood sample from herself and her infant once during the year. Infant serum levels averaged 1.5 mcg/L during the first month postpartum (n = 10); 3.95 mcg/L during the third month postpartum (n = 3); 4.2 mcg/L during the sixth month postpartum (n = 12); 2.5 mcg/L during the ninth month postpartum (n = 8); and, 3.6 mcg/L during the twelfth month postpartum (n = 11). Overall, the infants' serum levonorgestrel levels averaged 9.9% (range 4.9 to 12.6%) of simultaneous maternal serum levels.[23]

A study compared women who received levonorgestrel as a contraceptive via Norplant-2 (n = 14), an IUD that released 20 mcg daily (n = 14) or oral tablets containing 30 mcg of levonorgestrel (n = 10) at 4 to 6 weeks postpartum. The serum levels of infants averaged 0.046 mcg/L and 0.03 mcg/L in infants whose mothers used Norplant-2 and the IUD, respectively. Infants whose mothers used oral levonorgestrel had peak serum levels (i.e., 2-hour postnursing and 4 hours after maternal ingestion) serum levels of 0.02 mcg/L. Infant serum levels averaged 2.9 to 4.6%, 6.7% and 2.2% of maternal serum levels for Norplant-2, the IUD and oral tablets, respectively.[20]

Effects in Breastfed Infants

Numerous studies have found no systematic differences in growth, development or illness rates between the infants of mothers who received Norplant as a contraceptive and those of other mothers receiving either no contraception or nonhormonal contraception.[19][24][25][26][27][28] One study found serum thyroid stimulating hormone levels to be lower in the infants exposed to levonorgestrel than in control infants.[29]

Oral and Implant. A nonrandomized trial compared 250 breastfed infants whose mothers received 30 mcg daily of oral levonorgestrel initiated 7 days postpartum to 250 infants whose mothers received nonhormonal contraception. No differences in height and weight gain were seen during the 9-month study period between the 2 groups.[30]

Ten women received Norplant-2 beginning at 4 weeks postpartum. Mothers collected 4-hour urine samples daily from weeks 4 to 11 postpartum from their infants. Urine samples were analyzed for follicle-stimulating hormone, luteinizing hormone and testosterone. No difference was found in these levels when compared to those of infants whose mothers were taking either no contraception or an oral progestin-only contraceptive containing 30 mcg of levonorgestrel.[31]

Multicenter, nonrandomized studies followed infants whose mothers received levonorgestrel contraception during breastfeeding, either as oral tablets of 37.5 mcg daily (n = 246) or as Norplant (n = 453). No adverse effects on infant growth through the first year were found in comparison to standard measurements.[32][33] In a continuation study, infants from these studies who were exposed to levonorgestrel via Norplant (total n = 220) were followed up to 6 years of age. Infants were fully breastfed for an average of 7.8 months and were breastfed at least once daily for an average of 16.5 months. No differences in growth, diseases, surgery or hospitalizations were found from years 2 though 6 between infants whose mothers used levonorgestrel implants or Copper T IUD. An increase in skin conditions occurred in the levonorgestrel group and an increase in urogenital conditions occurred in the Copper T group.[28]

In a cohort study of 71 women who took levonorgestrel as a postcoital contraceptive found no obvious decrease in milk supply after the drug was used according to maternal reports 75% of mothers re-initiated breastfeeding before 8 hours after the dose. None noticed any adverse effect in their infants.[14]

IUD IUDs that released levonorgestrel were inserted 6 weeks after delivery. IUDs released 10 mcg per day (n = 30) or 30 mcg per day (n = 40); copper-releasing IUDs (n = 40) were used as controls. No differences were seen in infant height, weight, development, respiratory infections or blood chemistries up to 12 months of age between the levonorgestrel and copper IUD groups.[34]

Three hundred twenty lactating women were randomized to either an IUD containing levonorgestrel (Mirena; n =163) or the copper-containing IUD Cu T380A group (n =157). Follow-up of infants for 1 year found no differences in growth and development or in duration of breastfeeding.[35]

Effects on Lactation and Breastmilk

Numerous studies of varying size and quality have found that the use of levonorgestrel implants (Norplant or Norplant-2) as a contraceptive beginning at 7 days postpartum or later either has no clinically important negative effect on the quality of breastmilk and results in either no effect or an increase in the milk supply and duration of lactation.[25][27][30][36][37][38][39]

In a nonrandomized study, 100 women who received Norplant implants at an average of day 55 postpartum were compared to 100 women receiving a postpartum IUD. No differences were found between the control and Norplant groups in the number of women nursing at days 10 and 20 and months 1 to 12 postinsertion except a slight decrease in the number of mothers using Norplant who were exclusively breastfeeding at 12 months. No difference since the time of weaning was noted between the groups.[19]

IUDs releasing levonorgestrel were inserted 6 weeks after delivery. IUDs released 10 mcg per day (n = 30) or 30 mcg per day (n = 40); copper-releasing IUDs (n = 40) were used as controls. The rate of breastfeeding discontinuation was higher with the levonorgestrel groups than in the copper IUD group at 75 days, but not at other times.[34]

In a nonrandomized, nonblinded study comparing women who were breastfeeding at discharge, 102 postpartum women received depot medroxyprogesterone acetate (dosage not stated) in the early postpartum period (average 51.9 hours postpartum; range 6.25 to 132 hours), 181 received another progestin-only contraceptive and 138 used nonhormonal contraception. No differences in breastfeeding rates were seen at 2 and 6 weeks, but women receiving any hormonal contraceptive were breastfeeding at a lower rate (72.1% vs 77.6%) at 4 weeks postpartum. The authors concluded that progestin-only contraception initiated in the early postpartum period had no adverse effects on breastfeeding rates.[40]

In a small prospective study, forty-six women were randomized to have an IUD containing levonorgestrel (Mirena) inserted either within 10 minutes after placental delivery (n = 15), between 10 minutes and 48 hours after placental delivery (n = 15), or after 6 weeks postpartum (n = 16). At 6 months postpartum, no statistical difference in the rates of continued breastfeeding (extent not stated) was found among the groups.[8]

Women who gave birth were offered contraception with a levonorgestrel-containing IUD and randomized to have the IUD placed immediately following delivery (n = 46) or at 6 to 8 weeks postpartum (n = 50). Women randomized to later IUD insertion were more likely to be nursing at 6 months postpartum (24% vs 6%) and tended to have a longer median duration of exclusive breastfeeding.[9]

Among a cohort study of 71 women who took levonorgestrel as a postcoital contraceptive during nursing, none reported any obvious decrease in milk supply after the drug was used.[14]

A study of 1158 postpartum randomized women using the lactational amenorrhea method (LAM) for birth control randomized to be given levonorgestrel as a postcoital contraceptive or given nothing. No difference in the duration of breastfeeding was found between women who used the levonorgestrel and those who did not.[41]

A prospective, nonrandomized trial compared 4 contraceptives in 10 women each to assess their effect on milk production. One of the following were begun on day 42 postpartum as chosen by the mother: combined ethinyl estradiol 30 mcg plus levonorgestrel 150 mcg (Microvlar), etonogestrel implant (Implanon), levonorgestrel intrauterine system (Myrena), or a copper IUD (Optima). Milk intake was measured using deuterium oxide given to the mother and measured in the infants' saliva as well as numbers of wet diapers per day. Infants were also weighed and measured to assess growth. No differences in milk intake or infant growth were observed between the methods from days 42 through 63.[42]

Alternate Drugs to Consider

Etonogestrel Implant, Intrauterine Copper Contraceptive, Medroxyprogesterone Acetate, Norethindrone

References

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2. Queenan JT. Contraception and breastfeeding. Clin Obstet Gynecol. 2004;47:734-9. PMID: 15326435

3. Anon. FFPRHC Guidance (July 2004): Contraceptive choices for breastfeeding women. J Fam Plann Reprod Health Care. 2004;30:181-9. PMID: 15222930

4. Caird LE, Reid-Thomas V, Hannan WJ et al. Oral progestogen-only contraception may protect against loss of bone mass in breast-feeding women. Clin Endocrinol (Oxf). 1994;41:739-45. PMID: 7889609

5. Diaz S, Reyes MV, Zepeda A et al. Norplant(R) implants and progesterone vaginal rings do not affect maternal bone turnover and density during lactation and after weaning. Hum Reprod. 1999;14:2499-505. PMID: 10527977

6. Costa ML, Cecatti JG, Krupa FG et al. Progestin-only contraception prevents bone loss in postpartum breastfeeding women. Contraception. 2012;85:374-80. PMID: 22036473

7. ACOG Practice Bulletin No. 121: Long-acting reversible contraception: Implants and intrauterine devices. Obstet Gynecol. 2011;118:184-96. PMID: 21691183

8. Dahlke JD, Terpstra ER, Ramseyer AM et al. Postpartum insertion of levonorgestrel--intrauterine system at three time periods: a prospective randomized pilot study. Contraception. 2011;84:244-8. PMID: 21843688

9. Chen BA, Reeves MF, Creinin MD, Schwarz EB. Postplacental or delayed levonorgestrel intrauterine device insertion and breast-feeding duration. Contraception. 2011;84:499-504. PMID: 22018124

10. Farr S, Folger SG, Paulen M L et al. U S. medical eligibility criteria for contraceptive use, 2010: adapted from the World Health Organization medical eligibility criteria for contraceptive use, 4th edition. MMWR Recomm Rep. 2010;59 (RR-4):1-86. PMID: 20559203

11. Heinemann K, Westhoff CL, Grimes DA, Moehner S. Intrauterine devices and the risk of uterine perforations: Final results from the EURAS-IUD Study. Obstet Gynecol. 2014;123 (Suppl 1):3S. Abstract. PMID: 24770184

12. Stuart GS, Lesko C, Stuebe A, Bryant A. Breastfeeding and postpartum insertion of the levonorgestrel intrauterine system: a randomized trial. Obstet Gynecol. 2014;123 (Suppl 1):15S. Abstract. PMID: 24770058

13. Gainer E, Massai R, Lillo S et al. Levonorgestrel pharmacokinetics in plasma and milk of lactating women who take 1.5 mg for emergency contraception. Hum Reprod. 2007. PMID: 17337471

14. Polakow-Farkash S, Gilad O, Merlob P et al. Levonorgestrel used for emergency contraception during lactation-A prospective observational cohort study on maternal and infant safety. J Matern Fetal Neonatal Med. 2013;26:219-11. PMID: 22928541

15. Nilsson S, Nygren K-G, Johansson EDB. d-Norgestrel concentrations in maternal plasma, milk, and child plasma during administration of oral contraceptives to nursing women. Am J Obstet Gynecol. 1977;129:178-84. PMID: 900181

16. Saxena BN, Shrimanker K, Grudzinskas JG. Levels of contraceptive steroids in breast milk and plasma of lactating women. Contraception. 1977;16:605-13. PMID: 606500

17. Toddywalla VS, Mehta S, Virkar KD et al. Release of 19-nor-testosterone type of contraceptive steroids through different drug delivery systems into serum and breast milk of lactating women. Contraception. 1980;21:217-22. PMID: 7389350

18. Betrabet SS, Shikary ZK, Toddywalla VS et al. ICMR Task Force Study on hormonal contraception. Transfer of norethisterone (NET) and levonorgestrel (LNG) from a single tablet into the infant's circulation through the mother's milk. Contraception. 1987;35:517-22. PMID: 3117488

19. Diaz S, Herreros C, Juez G et al. Fertility regulation in nursing women: VII. Influence of Norplant levonorgestrel implants upon lactation and infant growth. Contraception. 1985;32:53-74. PMID: 3931973

20. Shikary ZK, Betrabet SS, Patel ZM et al. ICMR task force study on hormonal contraception. Transfer of levonorgestrel (LNG) administered through different drug delivery systems from the maternal circulation into the newborn infant's circulation via breast milk. Contraception. 1987;35:477-86. PMID: 3113823

21. Heikkila M, Haukkamaa M, Luukkainen T. Levonorgestrel in milk and plasma of breast-feeding women with a levonorgestrel-releasing IUD. Contraception. 1982;25:41-9. PMID: 6800691

22. Patel SB, Toddywalla VS, Betrabet SS et al. At what 'infant-age' can levonorgestrel contraceptives be recommended to nursing mothers. Adv Contracept. 1994;10:249-55. PMID: 7740991

23. Shaaban MM, Odlind V, Salem HT et al. Levonorgestrel concentrations in maternal and infant serum during use of subdermal levonorgestrel contraceptive implants, Norplant by nursing mothers. Contraception. 1986;33:357-63. PMID: 3089681

24. Abdulla KA, Elwan SI, Salem HS et al. Effect of early postpartum use of the contraceptive implants, Norplant, on the serum levels on immunoglobulins of the mothers and their breastfed infants. Contraception. 1985;32:261-6. PMID: 3936675

25. Shaaban MM, Salem HT, Abdullah KA. Influence of levonorgestrel contraceptive implants, Norplant, initiated early postpartum upon lactation and infant growth. Contraception. 1985;32:623-35. PMID: 3937665

26. Affandi B, Karmadibrata S, Prihartono J et al. Effect of Norplant on mothers and infants in the postpartum period. Adv Contracept. 1986;2:371-80. PMID: 3105266

27. Diaz S, Zepeda A et al. Fertility regulation in nursing women IX. Contraceptive performance, duration of lactation, infant gowth, and bleeding patterns during use of progesterone vaginal rings, progestin-only pills, Norplant implants, and Copper T 380-A intrauterine devices. Contraception. 1997;56:223-32. PMID: 9408703

28. Schiappacasse V, Diaz S, Zepeda A et al. Health and growth of infants breastfed by Norplant contraceptive implants users: a six-year follow-up study. Contraception. 2002;66:57-65. PMID: 12169382

29. Bassol S, Nava-Hernandez MP, Hernandez-Morales C et al. Effects of levonorgestrel implant upon TSH and LH levels in male infants during lactation. Int J Gynaecol Obstet. 2002;76:273-7. PMID: 11880130

30. McCann MF, Moggia AV, Higgins JE et al. The effects of a progestin-only oral contraceptive (levonorgestrel 0.03 mg) on breast-feeding. Contraception. 1989;40:635-48. PMID: 2515939

31. Shikary ZK, Betrabet SS, Toddywala VS et al. Pharmacodynamic effects of levonorgestrel (LNG) administered either orally or subdermally to early postpartum lactating mothers on the urinary levels of follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) in their breast-fed male infants. Contraception. 1986;34:403-12. PMID: 3096635

32. Anon. Progestogen-only contraceptives during lactation: I. Infant growth. World Health Organization Task force for Epidemiological Research on Reproductive Health; Special Programme of Research, Development and Research Training in Human Reproduction. Contraception. 1994;50:35-53. PMID: 7924321

33. Anon. Progestogen-only contraceptives during lactation: II. Infant development. World Health Organization, Task Force for Epidemiological Research on Reproductive Health; Special Programme of Research, Development, and Research Training in Human Reproduction. Contraception. 1994;50:55-68. PMID: 7924322

34. Heikkila M, Luukkainen T. Duration of breast-feeding and development of children after insertion of a levonorgestrel-releasing intrauterine contraceptive device. Contraception. 1982;25:279-92. PMID: 6804164

35. Shaamash AH, Sayed GH, Hussien MM, Shaaban MM. A comparative study of the levonorgestrel-releasing intrauterine system Mirena(R) versus the Copper T380A intrauterine device during lactation: breast-feeding performance, infant growth and infant development. Contraception. 2005;72:346-51. PMID: 16246660

36. Sas M, Gellen JJ, Dusitsin N et al. An investigation on the influence of steroidal contraceptives on milk lipid and fatty acids in Hungary and Thailand. WHO Special Programme of Research, Development and Research Training in Human Reproduction. Task Force on oral contraceptives. Contraception. 1986;33:159-78. PMID: 2938886

37. Anon. Effects of hormonal contraceptives on breast milk composition and infant growth. World Health Organization (WHO) Task Force on Oral Contraceptives. Stud Fam Plann. 1988;19:361-9. PMID: 2906764

38. Costa TH, Dorea JG. Concentration of fat, protein, lactose and energy in milk of mothers using hormonal contraceptives. Ann Trop Paediatr. 1992;12:203-9. PMID: 1381897

39. Chi IC, Robbins M, Balogh S. The progestin-only oral contraceptive--its place in postpartum contraception. Adv Contracept. 1992;8:93-103. PMID: 1519499

40. Halderman LD, Nelson AL. Impact of early postpartum administration of progestin-only hormonal contraceptives compared with nonhormonal contraceptives on short-term breast-feeding patterns. Am J Obstet Gynecol. 2002;186:1250-8. PMID: 12066106

41. Shaaban OM , Hassen SG, Nour SA et al. Emergency contraceptive pills as a backup for lactational amenorrhea method (LAM) of contraception: a randomized controlled trial. Contraception. 2013;87:363-9. PMID: 22935323

42. Bahamondes L, Bahamondes MV, Modesto W et al. Effect of hormonal contraceptives during breastfeeding on infant's milk ingestion and growth. Fertil Steril. 2013;100:445-50. PMID: 23623474

Levonorgestrel Identification

Substance Name

Levonorgestrel

CAS Registry Number

797-63-7

Drug Class

Contraceptive Agents, Female

Contraceptives, Oral, Synthetic

Contraceptives, Postcoital

Administrative Information

LactMed Record Number

421

Last Revision Date

20140515

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