Continuing metformin throughout pregnancy in women with polycystic ovary syndrome appears to safely reduce first-trimester spontaneous abortion: a pilot study.

Objective: To determine whether metformin would safely reduce the rate of first-trimester spontaneous abortion without teratogenicity in 19 women with the polycystic ovary syndrome (PCOS).

Methods: Prospective pilot study. Methods: Outpatient. Methods: Twenty-two previously oligoamenorrheic, nondiabetic women with PCOS; 125 women with PCOS who were not currently pregnant and who had > or = 1 previous pregnancy while they were not receiving metformin. Methods: Metformin, 1.5-2.55 g/day, throughout pregnancy. Methods: Rates of first-trimester spontaneous abortion and teratogenicity.

Results: Before metformin, 10 women had 22 previous pregnancies with 16 first-trimester spontaneous abortions (73%). While receiving metformin, these 10 women had 6 normal live births (60%), 1 spontaneous abortion (10%), and 3 normal ongoing pregnancies (30%) (all > or = 13 weeks; median gestation, 23 weeks). Among women receiving metformin, including those with live births and normal pregnancy for at least the first trimester, 1 of 10 (10%) had first-trimester spontaneous abortion compared with 73% in 22 previous pregnancies without metformin (P<.002). To date, the 19 women receiving metformin have had no adverse maternal side effects, and no birth defects have occurred; 9 (47%) had normal term live births, 2 (11%) had normal and appropriate for gestational age births (one at 33 and one at 35 weeks), 6 (32%) have ongoing normal pregnancies lasting longer than the first trimester, and 2 (10.5%) had first-trimester spontaneous abortions. Sonography showed normal fetal development without congenital defects in the 6 ongoing pregnancies (median gestation, 23 weeks). Among women who received metformin before conception, reductions in insulin and plasminogen activator inhibitor activity were correlated (r=0.65, P=.04).

Conclusions: Metformin therapy throughout pregnancy in women with PCOS reduces the otherwise high rate of first-trimester spontaneous abortion seen among women not receiving metformin and does not appear to be teratogenic.