M.E. Casado

Fertility regulation in nursing women: IX. Contraceptive performance, duration of lactation, infant growth, and bleeding patterns during use of progesterone vaginal rings, progestin-only pills, Norplant® implants, and Copper T 380-A intrauterine devices

This study evaluated the performance of progesterone vaginal rings (n = 187), progestin-only pills (n = 117), Norplant implants (n = 120), and Copper T 380-A intrauterine devices (n = 122) in lactating women. Contraceptive efficacy, bleeding pattern, and influence of the method upon breastfeeding duration and infant growth were compared with those of untreated women (n = 236) who relied on lactational infertility. Participants were healthy, 18 to 38 years, had had a normal delivery, and were intending to breastfeed for as long as possible. Contraceptives were initiated at day 57 +/- 3 postpartum. Results are reported for the first year of use. All methods were highly effective, with pregnancy rates below 1%. None affected breastfeeding performance or the rate of infant growth. Users of the progestin-only methods experienced a period of lactational amenorrhea 4 to 5 months longer than did users of Copper T or untreated women. More than half of the women in each contraceptive group reported a bleeding in the first month after treatment initiation, which was not considered in the calculation of the duration of amenorrhea. Prolonged or frequent bleedings were infrequent. The proportion of bleedings lasting more than 10 days ranged from 0 in the progestin-only pills group to 7% in the Norplant implants group. The four methods, initiated around the eighth postpartum week, provided effective contraception with no negative effects upon lactation or infant growth and without the bleeding problems associated with their use in nonlactating women.

FERTILITY REGULATION IN NURSING WOMEN: IV. Long-Term Influence of a Low-Dose Combined Oral Contraceptive Initiated at Day 30 Postpartum Upon Lactation and Infant Growth

The study was designed to test the long-term influence of a low-dose combined oral contraceptive upon lactation and infant growth when treatment was initiated at day 30 postpartum. The contraceptive tested contained ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg. Two control groups were formed by women who received an injectable placebo or a Copper T at day 30 postpartum. Women in the injectable placebo group received non-hormonal contraceptives at day 90 postpartum. An exacting list of requirements for admission and continuation in the study was applied to all groups. The oral contraceptive group had a significantly lower percentage of cases in full nursing from the 4th through the 10th postpartum month when compared to both control groups. The average absolute weight of infants in the oral contraceptive group was significantly lower at several ages when compared to the placebo group but not when compared to the Copper T group. No adverse side effects upon infants health were detected. It was concluded that the oral contraceptive tested showed a moderate inhibitory influence upon lactation when treatment was initiated at the beginning of the second postpartum month.

Lactational amenorrhea and the recovery of ovulation and fertility in fully nursing Chilean women

The probability of experiencing the first postpartum bleeding, the first ovulation and the risk of pregnancy during exclusive breastfeeding was assessed in a selected group of urban Chilean women. Admission criteria included having had a normal pregnancy and a vaginal term delivery of a healthy infant and the desire to maintain breastfeeding for as long as possible. The risk of bleeding and the recovery of ovulation was assessed in 48 women selected for being amenorrheic and fully nursing at day 75 postpartum and their willingness to participate in the blood sampling protocol. The first bleeding and ovulation was experienced while fully nursing by 28% and 26% of these subjects, respectively, at day 180 postpartum. The probability of experiencing the first bleeding and the probability of pregnancy during full nursing were calculated for 236 women not contracepting who were enrolled during the first month postpartum. The cumulative probability of bleeding and of pregnancy was 52% and 9.4% at day 180 postpartum, respectively. The risk of pregnancy was less than 2% in the subset of amenorrheic cases. In this urban population selected for having the highest motivation and best breastfeeding performance, the association of breastfeeding with infertility was too weak to serve as an effective birth spacer, except for the period of lactational amenorrhea. When the first postpartum bleeding took place before the sixth postpartum month in fully nursing women, it had a good predictive value to indicate the onset of a higher risk period.

Contraceptive efficacy of lactational amenorrhea in urban Chilean women

The contraceptive efficacy of breastfeeding was assessed in 236 healthy urban women who were followed at monthly intervals during the first postpartum year. Proportional hazard models were used to evaluate the influence of time postpartum, menstrual status and breastfeeding pattern upon the risk of pregnancy. Time and menstrual status had a highly significant effect on this risk. Those women who remained in amenorrhea had cumulative probabilities of pregnancy of 0.9% and 17% at 6 and 12 months postpartum, respectively. In those who recovered menstrual cycles, the risk rose to 36% and 55% at 6 and 12 months, respectively. Milk supplementation also increased significantly the risk when considered alone but not when time and/or menstrual status were included in the analysis. However, amenorrheic women who introduced bottle feeding, had a higher risk of pregnancy after 6 months postpartum than those who remained fully nursing. The analysis was unable to detect a significant influence of the nursing frequency. The results confirm that lactational amenorrhea is an effective contraceptive during the first six months postpartum. The first postpartum bleeding marks a great increase in the risk of pregnancy. Supplementation also increases the risk, particularly in amenorrheic women.

Fertility regulation in nursing women: VIII. Progesterone plasma levels and contraceptive efficacy of a progesterone-releasing vaginal ring

The objectives of this trial were to test the contraceptive efficacy and measure progesterone plasma levels of women using progesterone-releasing rings during lactation. Two types of rings delivering an average of about 5 mg or 10 mg of progesterone per day were tested in 128 healthy nursing women. A control group was formed by 127 Copper T users. Rings were inserted at day 60 postpartum and replaced every 3 months with a new one. Initially progesterone plasma levels were around 10 nmol/l and 15 nmol/l for rings releasing 5 and 10 mg per day, respectively, and decreased slightly after 30 days. Levels observed in subsequent segments of use approximated those of the first segment. These levels are within the range shown to inhibit fertility in lactating women. One pregnancy was diagnosed in 739 woman-months of progesterone ring use, and none occurred in 794 woman-months of Copper T use, which contrasts with the high incidence of pregnancy in a group of untreated nursing women where 19 pregnancies resulted during 677 woman-months. No deleterious effects were detected lactation and infant growth or maternal and infant health. It is concluded that the vaginal rings releasing progesterone are a suitable contraceptive method for lactating women.

Fertility regulation in nursing women: VII. Influence of NORPLANTR: Levonorgestrel implants upon lactation and infant growth

The objective of this study was to test the influence of NORPLANT implants upon lactation and infant growth. The results obtained during the first postpartum year are reported. One-hundred women were enrolled in the implant group. The control group was formed by 100 women who received a Copper T IUD. Treatments were administered at day 55 +/- 3. At admission all subjects were in exclusive breastfeeding with an adequate weight increase of the infant. No significant differences were found between the treated and control groups in the percentage of women in full nursing at different postpartum intervals, except for the 12th month postpartum where a lower percentage of cases from the NORPLANT group was in the full nursing category. No difference was found in the time of weaning. The infants showed a normal weight gain rate in both groups although the girls from the NORPLANT group showed a significantly lower daily weight increase during the 4th month than the girls from the IUD group. No pregnancies were diagnosed. No women asked for implant removal during the first year. No serious side effects related to treatment were detected. Bleeding irregularities were rare during breastfeeding which is in contrast with what occurs in non-nursing women treated with NORPLANT implants. Levonorgestrel concentrations found in milk were variable and individual values ranged from 23 to 311 pg/ml. The dose received by the infant can be estimated around 15 to 18 ng/Kg/day during the first month of treatment when the higher plasma values of levonorgestrel are observed. These levels is conjunction with the clinical observations reported here minimize the potential problems associated with levonorgestrel transference through maternal milk. Nevertheless, long-term studies are required to settle this matter and until more information is available, NORPLANT implant use in lactating women should be limited to cases who require a highly effective contraceptive method and where non-hormonal methods of similar effectiveness are contraindicated or unacceptable.

Fertility regulation in nursing women: III. Short-term influence of a low-dose combined oral contraceptive upon lactation and infant growth

The study was designed to test the short-term influence of a low-dose combined oral contraceptive upon lactation and infant growth when treatment was initiated at day 30 postpartum. The contraceptive tested contained ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg. Two control groups were formed by women who received either an oral placebo or an injectable placebo at day 30 postpartum. An exacting list of requirements for admission and continuation in the study was applied to all groups. The oral contraceptive group had a lower percentage of cases in exclusive breastfeeding at day 91 postpartum when compared to both control groups. Infants in the oral contraceptive group showed a significantly lower average absolute weight at days 61 and 91 postpartum and a significantly lower average daily weight increase during the first month of treatment when compared to both control groups. It was concluded that the oral contraceptive tested had a negative influence upon lactation and child growth.

BREASTFEEDING PATTERN AND THE DURATION OF LACTATIONAL AMENORRHEA IN URBAN CHILEAN WOMEN

The influence of the breastfeeding pattern and several clinical variables upon the duration of postpartum amenorrhea was assessed in a group of healthy women selected for having had a normal pregnancy and delivery and being highly motivated for prolonged breastfeeding on demand. 676 women who were fully nursing at the second month postpartum entered the study. Supplements were administered to 11% and 48% of the infants by the end of the 3rd and 6th month, respectively. The first bleeding was experienced before the end of the sixth month postpartum by 57% of the cases. Supplementation had a strong negative influence while nursing frequency had a significant positive influence upon the length of amenorrhea. Notwithstanding, a frequency of 8+ suckling episodes per 24 h could not maintain amenorrhea in around half of the subjects. Age and parity had a moderate negative influence upon the risk of experiencing the first postpartum bleeding. Maternal weight and ponderal index, infant sex, birth weight and growth rate showed no significant influence upon the length of amenorrhea. In this urban population selected for having the highest motivation and best breastfeeding performance, the association of breastfeeding with amenorrhea was weak in comparison with what has been described for other populations. The risk of experiencing the first bleeding was reduced while fully breastfeeding with a high number of nursing episodes per day and night, particularly in older women with higher parity. But even in such situation 25% and 50% of the women had started to cycle by the end of the fifth and eight postpartum month.

Fertility regulation in nursing women. VI. Contraceptive effectiveness of a subdermal progesterone implant.

Six progesterone pellets implanted subdermally were tested as contraceptive method for lactating women. One pregnancy was diagnosed in 1614 woman-months of observation, a failure rate which was similar to that observed in a contemporary group of Copper T users. Nineteen pregnancies were diagnosed in the 677 woman-months observed in untreated lactating women. The progesterone implants were effective when administered either at 30, 60 or 240 days after delivery. The duration of the effective life was 5 months and fertility was quickly restored afterwards. There were no deleterious effects upon maternal or infant health or upon lactation and the rate of child growth. The main problem encountered was the occurrence of pellet expulsion at a variable rate which appeared related to the manufacturing procedure.