Is Intrauterine Levonorgestrel safe while breastfeeding?

Effects on the breastfed infant

One study found serum thyroid stimulating hormone levels to be lower in the infants exposed to levonorgestrel than in control infants.[ 20 ] 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.[ 21 ] 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.[ 22 ]

Effects on milk supply

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.[ 21 ] 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.[ 10 ] 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.[ 13 ] A noninferiority trial compared breastfeeding in women who received a levonorgestrel IUD (product and dose not specified) immediately postpartum (n = 132) or at 8 weeks postpartum (n = 127). At 8 weeks, women who received the IUD immediately postpartum had a 5% lower rate of any breastfeeding (79% vs 84%), which fell withing the predetermined 15% noninferiority margin. Exclusive breastfeeding was slightly lower at 8 weeks in the immediate group (33% vs 40%), but the difference was not statistically significant. The time to lactogenesis in the immediate group was noninferior to that of the delayed group (65.3 vs 63.6 hours). Twenty-four device expulsions occurred in the immediate group compared to 2 in the delayed group (19% vs 2%), which was statistically significant.[ 11 ]

Levels in milk

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. Maternal Levels. 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.[ 17 ] A study of levonorgestrel IUDs compared levonorgestrel milk levels in women who had the IUD placed either within 30 minutes of delivery (immediate: n = 12) or at 4 to 8 weeks postpartum (delayed: n = 10). At 4 to 8 weeks postpartum, the median milk levonorgestrel level in the immediate group was 32.5 ng/L and the median in the delayed group s milk levels was 17.5 ng/L before IUD placement. Four weeks later, the two groups had similar median levels: 26.2 ng/L in the immediate group and 28 ng/L in the delayed group. It was not clear why the delayed group had measurable levonorgestrel levels before having the IUD placed. Measurements of milk creamatocrit found no effect of levonorgestrel on milk fat.[ 18 ] Infant Levels. 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 levonorgestrel serum levels averaged 0.03 mcg/L in infants whose mothers used the IUD. Infant serum levels averaged 6.7% of maternal serum levels.[ 19 ]

Alternatives LactMed lists

• Etonogestrel
• Intrauterine Copper Contraceptive
• Medroxyprogesterone Acetate
• Norethindrone