PREGNANCY OUTCOME IN NATURAL FAMILY-PLANNING USERS - COHORT AND CASE-CONTROL STUDIES EVALUATING SAFETY

Conceptions involving aging gametes are of relevance to natural family planning (NFP) because women using NFP to avoid pregnancy abstain fro m intercourse during the fertile time of the cycle. To help verify the safety of pregnancies occurring among NFP practitioners, our group ha s, since 1986, conducted a large cohort study involving six experience d NFP centers. Timing of conception was determined from NFP charts, in which women recorded days on which intercourse occurred. The number o f days from the most probable conception intercourse to probable day o f ovulation was first determined, and used as an estimate of the time gametes remained in the genital tract before fertilization. Several st udies have already been completed, cohort as well as case-control in n ature. 1. Spontaneous abortions. Three hundred and sixty-one conceptio ns occurred during the optimal time (day -1 or 0 relative to ovulation ), and of these 33 resulted in spontaneous abortion (9.1%). Five hundr ed and seven conceptions occurred at non-optimal times during the cycl e, and of these 55 resulted in spontaneous abortions (10.9%). These di fferences were not statistically significant (relative risk 1.19, 95% CI, 0.79-1.80) [1]. 2. Anomalies. Among 780 singleton births in 868 co hort pregnancies, 24 infants had major anomalies (3.1%) as of the pres ent analysis [2]. This frequency is comparable to the general populati on. To further assess anomalies we employed a case-control approach. A ll consecutive births (live and stillborn) weighing 500 g or more taki ng place in 18 participating South American hospitals were examined fo r minor and major congential anomalies. Mothers of malformed and contr ol infants did not differ with respect to the reported frequency of NF P use, which overall was 6.3% of the 10 642 mothers interviewed (5277 having a malformed infant; 5371 controls). Of 262 discordant pairs, th ere were 28 or 10.69% mothers within the Down syndrome case group vs. 16/262 or 6.11% among matched controls [3,4]. The odds ratio was 1.84; 95% CI, 0.99-3.96; however, even this non-significant difference narr owed substantially when adjusted for maternal age (OR, 1.78; 95% CI, 0 .84-3.75); parity (OR, 1.68; 95% CI, 0.87-3.24); maternal educational level (OR, 1.71; 95% CI, 0.86-3.44); or all three together (OR, 1.74; 95% CI, 0.83-3.64). Conclusions. Our findings should be reassuring to natural family planning users. The overall rate of spontaneous abortio n was not increased in NFP users who became pregnant, nor to date was the rate of anomalies. Any contribution to Down syndrome or abortion d ue to aging gametes would have to be small.