ABSTRACT
Progesterone regulates uterine function during the luteal phase and is essential for the acquisition of endometrial receptivity. The objective of the present study was to identify endometrial transcripts whose expression is altered during the window of implantation after the administration of 200 mg of the antiprogestin mifepristone, 48 h after the LH peak (LH+2, LH+0=LH peak), and to determine the relationship of these transcripts with those regulated during the acquisition of receptivity. Endometrial samples were obtained in LH+7 from seven women of proven fertility, each one contributing with one cycle treated with placebo and another with mifepristone. Additionally, endometrial samples were obtained in LH+2 and LH+7 during a single untreated spontaneous cycle from seven normal fertile women as a reference. DNA microarrays were used to identify transcripts significantly regulated (defined as ≥ 2.0-fold change with false discovery rate below 1% using t-test) with the administration of mifepristone vs placebo, or during the transition from pre-receptive to receptive (LH+2 vs LH+7). Approximately 2000 transcripts were significantly regulated in both comparisons (mifepristone vs placebo and LH+2 vs LH+7), but only 777 of them were coincident and displayed opposite regulation except for 25. The mRNA level for eight selected genes regulated by mifepristone was confirmed by real-time RT-PCR. We conclude that not all changes in endometrial transcript levels occurring in the transition from LH+2 to LH+7 seem to be regulated by the progesterone receptor and â¼ 37% of the genes whose transcript levels changed by effect of mifepristone could be associated with the acquisition of receptivity.
Subject(s)
Biomarkers/metabolism , Endometrium/metabolism , Gene Expression Profiling , Hormone Antagonists/pharmacology , Menstrual Cycle/genetics , Mifepristone/pharmacology , Ovulation/genetics , Cross-Over Studies , Double-Blind Method , Endometrium/drug effects , Female , Humans , Luteal Phase/drug effects , Luteal Phase/genetics , Menstrual Cycle/drug effects , Oligonucleotide Array Sequence Analysis , Ovulation/drug effects , Real-Time Polymerase Chain ReactionABSTRACT
BACKGROUND: There is evidence that cyclooxygenase-2 (COX-2) inhibitors can prevent or delay follicular rupture. COX-2 inhibitors, such as meloxicam, may offer advantages over emergency contraception with levonorgestrel, such as extending the therapeutic window for up to 24 h. We assessed the effect of meloxicam administered in the late follicular phase upon ovulation in women. MATERIALS AND METHODS: This was a single center, double blind, crossover study designed to assess the effects in 27 eligible women (18-40 years old, surgically sterilized with regular menstrual cycles) of meloxicam, 15 or 30 mg/day, administered orally for five consecutive days during the late follicular phase, starting when the leading follicle reached 18 mm diameter. Volunteers underwent two treatment cycles separated by one resting cycle, with randomization to dose sequence. Main outcomes were follicular rupture; serum LH, progesterone and estradiol (E2) levels; and incidence of adverse events. RESULTS: Twenty-two volunteers completed the study. There were no differences between meloxicam doses in menstrual cycle length. Dysfunctional ovulation was observed in 11/22 (50%) cycles treated with 15 mg/day and 20/22 (90.9%) cycles with 30 mg/day (P = 0.0068). All women had normal luteal phase progesterone levels; mean maximal values +/- SEM were 42 +/- 4.1 and 46.8 +/- 2.6 nmol/l for 15 and 30 mg/day groups, respectively. There were no serious adverse events, and no changes in LH and E2 levels or in cycle length. CONCLUSIONS: Meloxicam 30 mg given for five consecutive days in the late follicular phase is safe, effective and may be an alternative form of emergency contraception.
Subject(s)
Cyclooxygenase 2 Inhibitors/pharmacology , Ovarian Follicle/drug effects , Ovulation/drug effects , Thiazines/pharmacology , Thiazoles/pharmacology , Adolescent , Adult , Contraception, Postcoital , Cross-Over Studies , Double-Blind Method , Estradiol/blood , Female , Follicular Phase/drug effects , Humans , Luteinizing Hormone/blood , Meloxicam , Ovarian Follicle/physiology , Progesterone/blood , Thiazines/adverse effects , Thiazoles/adverse effectsABSTRACT
BACKGROUND: Gene expression profiling of normal receptive endometrium has been characterized, but intrinsic defects in endometrial gene expression associated with implantation failure have not been reported. METHODS: Women who had previously participated as recipients in oocyte donation cycles and repeatedly exhibited implantation failure (Group A, study group) or had at least one successful cycle (Group B, control group) and spontaneously fertile women (Group C, normal fertility group) were recruited. All were treated with exogenous estradiol and progesterone to induce an endometrial cycle, and an endometrial biopsy was taken on the seventh day of progesterone administration. RNA from each sample was analysed by cDNA microarrays to identify differentially expressed genes between groups. RESULTS: 63 transcripts were differentially expressed (>or=2-fold) between Groups A and B, of which 16 were subjected to real time RT-PCR. Eleven of these were significantly decreased in Group A with regard to Groups B and C. Among the dysregulated genes were MMP-7, CXCR4, PAEP and C4BPA. CONCLUSIONS: Repeated implantation failure in some oocyte recipients is associated with an intrinsic defect in the expression of multiple genes in their endometrium. Significantly decreased levels of several transcripts in endometria without manifest abnormalities is demonstrated for the first time and shown to be associated with implantation failure.
Subject(s)
Embryo Implantation , Endometrium/metabolism , Gene Expression Profiling , Pregnancy , RNA, Messenger/metabolism , Adult , Complement C4b-Binding Protein , Female , Glycodelin , Glycoproteins/genetics , Histocompatibility Antigens/genetics , Humans , Matrix Metalloproteinase 7/genetics , Middle Aged , Oligonucleotide Array Sequence Analysis , Pregnancy Proteins/genetics , Receptors, CXCR4/genetics , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
OBJECTIVE: The study was conducted to assess levonorgestrel (LNG) serum levels achieved after a single administration of two different doses of Carraguard vaginal gel containing LNG (CARRA/LNG), designed for use as microbicide and contraceptive for potential dual protection. MATERIALS AND METHODS: This was a randomized double-blind pharmacokinetic study conducted in 12 subjects enrolled at two centers. Each subject received a single vaginal administration of CARRA/LNG containing either 0.75 or 1.5 mg LNG per 4 mL of gel on Days 10-12 of the menstrual cycle. LNG serum levels were measured at 0, 1, 2, 4, 8 and 12 h after administration and for the following 7 days. LH and progesterone (for a preliminary evaluation of effect on the ovarian function) as well as SHBG were measured in the daily samples. RESULTS: Serum LNG maximum concentrations (Cmax) were 14.1+/-2.1 and 11.7+/-2.7 nmol/L and Tmax was 12.0 and 6.0 h for the low and high dose, respectively, with large intersubject variability within the first 48 h. Mean levels at 96 h were 10% of Cmax. Differences in AUC between both doses were not statistically significant. SHBG levels decreased approximately 25% by Day 4 after administration. Luteal activity was observed in 3/6 and 5/6 of the subjects in the low- and high-dose group, respectively. CONCLUSION: This study demonstrates that the CARRA/LNG gel can sustain elevated serum levels of the contraceptive steroid for up to 96 h after a single application. The serum levels attained with the 0.75-mg formulation are in the range expected to perturb the ovulatory process as observed in some subjects. The lack of correlation between the administered dose and serum concentrations of the steroid may be related to a rate-limiting absorption of LNG from the vaginal mucosa. The results reported here suggest that the CARRA/LNG formulation has good potential to become a dual-protection method, possibly preventing conception and sexually transmitted infections.
Subject(s)
Anti-Infective Agents/pharmacokinetics , Levonorgestrel/pharmacokinetics , Administration, Intravaginal , Anti-Infective Agents/administration & dosage , Anti-Infective Agents/blood , Area Under Curve , Chemistry, Pharmaceutical , Chile , Contraceptives, Postcoital, Synthetic/administration & dosage , Contraceptives, Postcoital, Synthetic/blood , Contraceptives, Postcoital, Synthetic/pharmacokinetics , Dominican Republic , Double-Blind Method , Female , Humans , Intestinal Absorption , Levonorgestrel/administration & dosage , Levonorgestrel/blood , Vaginal Creams, Foams, and JelliesABSTRACT
OBJECTIVE: The study was conducted to evaluate the effect of Carraguard vaginal gel containing 0.75 mg of levonorgestrel (CARRA/LNG gel) administered in a single dose at different stages of follicle development over subsequent follicle rupture and hormonal levels. METHOD: Randomized, blinded, cross-over study comparing the effects of a single administration of CARRA/LNG gel or Carraguard (CARRA) gel. Twenty-four healthy women were enrolled in two centers. The gels were administered when the follicle had reached diameters of 12-14, 15-17 and > or =18 mm in eight women each. Volunteers were followed for one treatment, one washout cycle and a second treatment cycle. Follicle rupture or nonrupture was assessed by transvaginal ultrasound. Luteinizing hormone, estradiol and progesterone levels were measured daily for 5 days following treatment, and three times per week until menses. RESULTS: No follicular rupture within the 5-day period following administration was observed in 74% and 30% of the CARRA/LNG and CARRA gel treatment cycles, respectively, while ovulation was documented in 4% and 61%, respectively. The overall proportion of cycles with lack of follicular rupture or ovulatory dysfunction (follicle rupture preceded by an inadequate LH surge) was 96% for CARRA/LNG and 39% in the CARRA gel cycles. CONCLUSION: Single vaginal administration of 0.75 mg LNG in CARRA gel in the late follicular phase is effective for interfering with the ovulatory process.
Subject(s)
Contraceptive Agents, Female/administration & dosage , Levonorgestrel/administration & dosage , Ovarian Follicle/drug effects , Ovulation/drug effects , Administration, Intravaginal , Adult , Contraception, Postcoital , Contraceptive Agents, Female/adverse effects , Contraceptive Agents, Female/blood , Cross-Over Studies , Female , Humans , Levonorgestrel/adverse effects , Levonorgestrel/blood , Menstrual Cycle/drug effectsABSTRACT
OBJECTIVE: The Nestorone/ethinylestradiol (NES/EE) vaginal ring is being developed as a regular contraceptive method by the Population Council. This ring is designed to release NES 150 microg/day and EE 15 microg/day during 1 year. Here, we report a Phase I clinical trial to determine the usefulness of this ring for emergency contraception. To that end, we tested the ability of this ring to interfere with ovulation when it is inserted during the follicular phase. METHOD: Forty-eight women protected from the risk of pregnancy by nonhormonal methods were divided into three groups, which differed by the size of the dominant follicle at the time of ring insertion: 12-14 mm (n = 16), 15-17 mm (n = 18) and >or=18 mm (n = 14) diameter. The NES/EE ring was left in the vagina for 7 consecutive days, after which it was removed. The growth of the leading follicle and plasma levels of estradiol, progesterone (P), luteinizing hormone (LH) and follicle stimulating hormone (FSH) in the ensuing 5 days after ring insertion were determined. Afterwards, steroid hormones were measured twice a week, until menses took place. All women had a control cycle before the ring cycle, and the range of maximum follicular diameter assigned to each volunteer was the same for the control and the ring cycle at the time when placebo was ingested or the ring inserted. RESULTS: During the 5-day period after ring insertion with follicles 12-17 mm, ovulation was absent in 25 of 34 cycles (p < .01 vs. control), and ovulatory dysfunction (absent, blunted or mistimed LH peak) occurred in 8 of the 9 remaining cycles (33/34 ovulatory processes altered; p < .005 vs. control). After ring insertion with follicles >or=18 mm in diameter, ovulation did not occur in 2 of 14 cycles or was dysfunctional in 7 of the 12 remaining cycles (9/14 ovulatory processes altered; p<.025 vs. control). Altogether, 87.5% of ring cycles (42/48) had either no ovulation or ovulatory dysfunction in the 5-day study period, in contrast to 39.6% (19/48 cycles) in control cycles (p < .001). Among follicles that failed to rupture within the 5-day study period, none ruptured later on in the ring-treated cycles, while 9 of 16 did so in control cycles. Sixty-two percent of ring-treated cycles were shorter than 24 days. Nausea, vaginal discharge and abdominal pain were the most frequently reported adverse events during ring use. CONCLUSION: Interference with 87.5% of ovulatory processes, without ovulation occurring later in the cycle and shortening of cycle length, suggests the NES/EE ring may be used as an emergency contraceptive method, with the potential advantage of providing continuing contraception after it has performed its emergency function.
Subject(s)
Contraception, Postcoital/methods , Ethinyl Estradiol/administration & dosage , Norprogesterones/administration & dosage , Administration, Intravaginal , Adult , Estradiol/blood , Ethinyl Estradiol/adverse effects , Ethinyl Estradiol/blood , Female , Follicle Stimulating Hormone/blood , Humans , Luteinizing Hormone/blood , Menstrual Cycle , Norprogesterones/adverse effects , Norprogesterones/blood , Ovarian Follicle/diagnostic imaging , Ovulation , Progesterone/blood , Ultrasonography , Uterine Hemorrhage/epidemiologyABSTRACT
BACKGROUND: The contraceptive efficacy of emergency contraceptive pills containing levonorgestrel (LNG-EC) has been estimated in most previous studies by judging the day of ovulation from presumptive menstrual cycle data, thus providing poorly reliable estimates. METHODS: In the present study, the efficacy of LNG-EC was determined in 393 cycles by dating ovulation on the basis of reliable hormonal and ovarian parameters validated by a database constructed in a separate study. In addition, the efficacy was determined separately for cycles in which LNG-EC was given before or after ovulation. RESULTS: For the 148 women who had sexual intercourse during the fertile days, the overall accumulated probability of pregnancy was 24.7, while altogether 8 pregnancies were observed. Thus, the overall contraceptive efficacy of LNG-EC was 68%. Among the 103 women who took LNG-EC before ovulation (days -5 to -1), 16 pregnancies were expected and no pregnancy occurred (p<.0001). Among the 45 women who took LNG-EC on the day of ovulation (day 0) or thereafter, 8 pregnancies occurred and 8.7 were expected (p=1.00). These findings are incompatible with the inhibition of implantation by LNG-EC in women. The same cases were also analyzed using the presumptive menstrual cycle data, and important discrepancies were detected between the two methods. CONCLUSION: The efficacy of LNG-EC has been overestimated in studies using presumptive menstrual cycle data. Our results confirm previous similar studies and demonstrate that LNG-EC does not prevent embryo implantation and therefore cannot be labeled as abortifacient.
Subject(s)
Contraceptive Agents, Female/administration & dosage , Contraceptives, Oral, Synthetic/administration & dosage , Contraceptives, Postcoital/administration & dosage , Levonorgestrel/administration & dosage , Menstrual Cycle , Ovulation , Adolescent , Adult , Emergency Treatment , Female , Humans , Pregnancy , Pregnancy Outcome , Young AdultABSTRACT
BACKGROUND: We aimed to evaluate whether emergency contraception with levonorgestrel (LNG-EC) administered after ovulation is equally effective to LNG-EC administered before ovulation. STUDY DESIGN: We studied a cohort of women attending a family planning clinic for EC. From interview, we recorded menstrual history, time of intercourse and of intake of LNG-EC. On the day of intake of LNG-EC and during 5 days' follow-up, blood samples were taken for examination of luteinizing hormone, estradiol and progesterone concentrations, and vaginal ultrasound examinations were done for size of the leading follicle and/or corpus luteum. Thereafter women were not contacted until next menses or pregnancy occurred. RESULTS: Of 388 women attending for LNG-EC, 122 women had intercourse on fertile cycle days according to ultrasound and endocrine findings. At the time of LNG-EC intake, 87 women were in Days -5 to -1 and 35 women were in Day 0 (day of ovulation) or beyond. With the use of the probability of clinical pregnancy reported by Wilcox et al. [N Engl J Med 333 (1995) 1517-1521], expected numbers of pregnancies among the 87 and 35 women were 13 and 7, respectively, while 0 and 6 pregnancies, respectively, occurred. CONCLUSION: We conclude that LNG-EC prevents pregnancy only when taken before fertilization of the ovum has occurred.
Subject(s)
Contraception, Postcoital , Contraceptive Agents, Female/administration & dosage , Levonorgestrel/administration & dosage , Menstrual Cycle , Ovulation , Adolescent , Adult , Coitus , Female , Humans , Prospective Studies , Young AdultABSTRACT
La concentración de Osteocalcina (OC) es un buen marcador del remodelamiento óseo. La influencia del estradiol sobre la OC ha sido descrita en el embarazo, lactancia y postmenopausia. No existe acuerdo si los cambios en la concentración plasmática de estradiol del ciclo menstrual normal se relacionan con modificaciones de la OC. En este estudio la OC sérica fue medida seriadamente a lo largo de un ciclo mesntrual normal en 4 voluntarias sanas, libres de toda medicación (edad 33-38 años). Durante el estudio las mujeres mantuvieron su dieta y actividad física habitual. A partir del día 4 ó 5 del ciclo, se tomaron muestras de sangre entre las 09 y 11 am, cada 2 ó 3 días, para determinación de OC, FSH, LH, E2 y P. Se realizó seguimiento folicular ecográfico día por medio entre los días 7 y 18 del ciclo. Las determinaciones hormonales fueron realizadas por RIA utilizando reactivos aportados por la OMS. La OC fue determinada por RIA (incstar OC 125 I Kit, Incstar, Stillwater, MN) con límite de sensibilidad de 0,78 ng/ml y coeficiente de variación intraensayo de 4,6%. Todas las muestras fueron corridas en el mismo ensayo. El análisis estadístico incluyó la prueba de Kolmogorow-Smirnow (KS) y el coeficiente de correlación temporal de Sperman (S). Las concentraciones sanguíneas de FSH, LH, E2 y P cambiaron durante el estudio de acuerdo al caráter ovulatorio del ciclo. Como se muestra en la Tabla 1, las concentraciones de OC permanecieron estables a lo largo del ciclo en cada una de las 4 mujeres. Los valores de OC se expresan como promedio ñ ES de todas las muestras tomadas a lo largo del ciclo de cada mujer. d*: diferencia absoluta máxima entre el valor observado y la distribución teórica normal según la prueba de Kolmogorov. r**:, coeficiente de correlación temporal para los valores de OC. En conclusión, aparece como independiente de las variaciones de las gonadotrofinas y esteroides ováricos del ciclo menstrual normal. De este modo, la evaluación de la formación ósea no debería ser influenciada por el día o la fase del ciclo menstrual en el cual la muestra es obtenida
Subject(s)
Humans , Female , Adult , Menstrual Cycle , Osteocalcin/blood , Estradiol/blood , Follicle Stimulating Hormone/blood , Phosphorus/blood , Luteinizing Hormone/blood , RadioimmunoassayABSTRACT
La concentración de Osteocalcina (OC) es un buen marcador del remodelamiento óseo. La influencia del estradiol sobre la OC ha sido descrita en el embarazo, lactancia y postmenopausia. No existe acuerdo si los cambios en la concentración plasmática de estradiol del ciclo menstrual normal se relacionan con modificaciones de la OC. En este estudio la OC sérica fue medida seriadamente a lo largo de un ciclo mesntrual normal en 4 voluntarias sanas, libres de toda medicación (edad 33-38 años). Durante el estudio las mujeres mantuvieron su dieta y actividad física habitual. A partir del día 4 ó 5 del ciclo, se tomaron muestras de sangre entre las 09 y 11 am, cada 2 ó 3 días, para determinación de OC, FSH, LH, E2 y P. Se realizó seguimiento folicular ecográfico día por medio entre los días 7 y 18 del ciclo. Las determinaciones hormonales fueron realizadas por RIA utilizando reactivos aportados por la OMS. La OC fue determinada por RIA (incstar OC 125 I Kit, Incstar, Stillwater, MN) con límite de sensibilidad de 0,78 ng/ml y coeficiente de variación intraensayo de 4,6%. Todas las muestras fueron corridas en el mismo ensayo. El análisis estadístico incluyó la prueba de Kolmogorow-Smirnow (KS) y el coeficiente de correlación temporal de Sperman (S). Las concentraciones sanguíneas de FSH, LH, E2 y P cambiaron durante el estudio de acuerdo al caráter ovulatorio del ciclo. Como se muestra en la Tabla 1, las concentraciones de OC permanecieron estables a lo largo del ciclo en cada una de las 4 mujeres. Los valores de OC se expresan como promedio ñ ES de todas las muestras tomadas a lo largo del ciclo de cada mujer. d*: diferencia absoluta máxima entre el valor observado y la distribución teórica normal según la prueba de Kolmogorov. r**:, coeficiente de correlación temporal para los valores de OC. En conclusión, aparece como independiente de las variaciones de las gonadotrofinas y esteroides ováricos del ciclo menstrual normal. De este modo, la evaluación de la formación ósea no debería ser influenciada por el día o la fase del ciclo menstrual en el cual la muestra es obtenida (AU)
Subject(s)
Humans , Female , Adult , Osteocalcin/blood , Menstrual Cycle , Follicle Stimulating Hormone/blood , Luteinizing Hormone/blood , Estradiol/blood , Phosphorus/blood , RadioimmunoassayABSTRACT
El presente trabajo estudia la influencia de Norplant (R) sobre la lactancia y sobre el crecimiento del lactante durante el primer año post parto. 100 mujeres en lactancia exclusiva recibieron Norplant (R) el día 55 + ou - 3 post parto y a 100 mujeres con similares características se les insertó una T cobre. No hubo diferencias significativas en la evolución de la lactancia entre los dos grupos hasta el 12§ mes post parto en que el grupo Norplant observó un menor porcentaje de mujeres en lactancia exclusiva. Los niños presentaron un crecimiento ponderal normal en los dos grupos, aunque las hijas del grupo Norplant crecieron significativamente menos durante el 4§ mes de vida, al compararlas con las hijas de mujeres portadoras de DIU. No se diagnosticaron embarazos ni efectos colaterales relevantes. En la leche materna se detectaron concentraciones variables de levonorgestrel con valores que fluctuaron entre 23 y 311 pc/ml. La dosis recibida por el niño se estimó en 15 a 18 ng/Kg/día durante el primer mes de uso de Norplant (R), dosis baja que probablemente no representa riesgo para la salud de los niños, aunque se necesita más investigación sobre el tema. Hasta el momento, el uso de Norplant durante la lactancia debería limitarse a aquellos casos que necesitan protección efectiva y que otros métodos anticonceptivos no hormonales estén contraindicados o no sean aceptados
Subject(s)
Pregnancy , Infant, Newborn , Infant , Adolescent , Adult , Humans , Female , Child Development , Contraceptive Devices, Female , LactationABSTRACT
El objetivo de este ensayo fue investigar los niveles plasmáticos de progesterona y la eficacia anticonceptiva de anillos vaginales liberando progesterona durante la lactancia. Se probaron dos tipos de anillos, que liberaban un promedio aproximado de 5 ó 10 mg. diarios, respectivamente, en 165 mujeres sanas, en plena lactancia. Se constituyó un grupo control de 162 portadores de DIU - T/Cobre. Los anillos fueron insertados el día 60- posparto, y renovados cada tres meses por otros. Al comienzo del ensayo, los niveles plasmáticos de progesterona eran, aproximadamente, 10 nmol/L y 15 nmol/L para anillos que liberaban, respectivamente, 5 y 10 mg por día, y se reducían ligeramente después de 30 días. Los niveles en períodos de uso subsecuentes, observados, se acercaban a los del primer período o etapa. Estos niveles varían dentro de la amplitud eficaz para inhibir la fertilidad de mujeres en lactancia. Se diagnosticó un embarazo en 1005 meses-mujer de uso del anillo de progesterona, y no ocurrió ninguno en 1075 meses-mujer de uso de T/Cu. Esto contrasta con la alta incidencia de embarazos comprobada en un grupo de mujeres en lactancia, sin tratamiento, en quienes se gestaron 19 embarazos, o sea, una incidencia en 677 meses-mujer. No se detectaron efectos deletéreos sobre la lactancia ni sobre el crecimiento de los niños, como tampoco sobre la salud materna o infantil. La conclusión es que el anillo vaginal de progesterona es un método adecuado para el suministro de progesterona como anticonceptivo para madres en lactancia
Subject(s)
Adult , Humans , Female , Contraception/methods , Breast Feeding , Progesterone/blood , Chile , Clinical Trials as TopicABSTRACT
Se midió la influencia del amamantamiento sobre la duración de la amenorrea en un grupo de mujeres altamente motivadas para amamantar en libre demanda por un tiempo prolongado. Se calculó la probabilidad de presentar el primer sangrado en 676 mujeres en lactancia exclusiva al segundo mes postparto. El 52% presentó el primer sangrado estando en lactancia exclusiva, antes del término del sexto mes postparto. El tiempo transcurrido desde el parto y la suplementación influyeron negativamente en la duración de la amenorrea. Frecuencias de ocho o más mamadas en 24 hooras no lograron prolongar la amenorrea en todos los casos. El reinicio de los ciclos ovulatorios se estudió en 48 mujeres en amenorrea y lactancia exclusiva al tercer mes postparto. El 28% de las mujeres presentó el primer sangrado, y el 26% de los casos ovuló antes del término del sexto mes postparto. La probabilidad acumulada de embarazo fue de 9,4% al sexto mes postparto en las mujeres en lactancia exclusiva que no usaron métodos anticonceptivos. El riesgo fue menor del 2% en aquellos casos que permanecieron en amenorrea durante este período. En la población estudiada la lactancia no resultó un método eficaz para espaciar los nacimientos, con excepción de los casos que se mantuvieron con lactancia exclusiva y amenorrea