Conception control

Published on 10/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 10/03/2015

Print this page

This article have been viewed 5540 times

Chapter 31 Conception control

The availability of safe modern contraceptives has enabled women to avoid unwanted pregnancy, and couples to space their children. Spacing children to intervals of 2 or more years improves a woman’s health.

Contraceptive choices now available permit the woman, or the couple, to choose the most appropriate contraceptive for their particular circumstances. Younger women usually prefer oral contraceptives or expect their male partners to use condoms, whereas older women are more inclined to choose the intrauterine device (IUCD) or a permanent method of birth control, such as tubal ligation or a vasectomy in her partner (Fig. 31.1).

Fig. 31.1 Methods of fertility control in Britain.

Before choosing a particular contraceptive most people want to know its effectiveness in preventing pregnancy, its safety, and the side-effects associated with its use. A method of evaluating the effectiveness of the various contraceptive methods is the Pearl Index, which calculates the unintended pregnancy rate from the formula:

The result is expressed as the failure rate per 100 woman years (HWY).

Table 31.1 shows the effectiveness of various contraceptive methods in preventing pregnancy.

Table 31.1 Ranking of contraceptive methods by rate of effectiveness

		Failure Rates per 100 HWY
Group A	Most effective
	Tubal ligation/ vasectomyCombined oralContinuous progesterone	0.005–0.04
	Combined oral	0.005–0.30
	Continuous progesterone	0.07
Group B	Highly effective
	IUCD	0.5–3.5
	Depot progestogen	1.5–2.3
	Diaphragm or comdom	1.5–2.3
	All users	4.0–7.0
	Highly motivated	1.5–3.0
	Periodic abstinence	1.5–3.0
	All users	10.0–30.0
	Highly motivated	2.5–5.0
Group C	Less effective
	Coitus interruptus	30.0–40.0
	Vaginal foam or cream	30.0–40.0
Group D	Least effective
	Postcoital douche	45.0
	Prolonged breastfeeding	45.0

Some women find it embarrassing to consult a medical practitioner about contraception and a sensitive doctor will do everything possible to diminish that embarrassment. The ability to listen to and to talk with the woman is of great importance.

The doctor should take a general history, a menstrual history and a sexual history in a non-judgemental way. With this information, the doctor will be better able to help the woman decide which method of contraception she would prefer.

A gynaecological examination should be made, although if the woman is teenaged and has not previously had a vaginal examination it can be deferred to a subsequent visit. If she has not had a Pap smear taken in the previous 2 years, the doctor should suggest that this be done, explaining how the smear is taken and the reason for it.

REVERSIBLE METHODS OF CONTRACEPTION USED BY THE COUPLE

Periodic abstinence

It is known that if a woman has a menstrual cycle of normal duration, ovulation occurs 14 ± 3 days before the start of her next menstruation. It is also known that pregnancy is most likely to occur if intercourse takes place in the 5 days before ovulation or on the day of ovulation. This interval is called the fertile period. This has led to the idea of periodic abstinence during the fertile period as a method of birth control.

The woman is taught to detect the presence of mucus at the vaginal entrance each morning (before any sexual arousal). Three types of mucus can be detected and, from this, the days on which sexual intercourse can take place can be calculated while to some extent avoiding the chance of an unwanted pregnancy (Fig. 31.2). The compliance of the man is essential if pregnancy is to be avoided.

Fig. 31.2 Periodic abstinence: the mucus (ovulation) method.

Because of the difficulties in assessing the mucus and the need for the man to cooperate fully, the pregnancy rate varies from 10 to 30 per HWY for all couples, but for motivated couples it is 2.5–5.0 per HWY.

Coitus interruptus

Withdrawal, or coitus interruptus, is the oldest form of birth control apart from induced abortion. With the development of more modern contraceptives its frequency has declined, but it is still the preferred method in some sections of society. Its reliability for preventing pregnancy depends on the ability of the man to recognize the pre-ejaculatory phase and his agility in withdrawing his penis from the woman’s vagina before ejaculation. Because of these constraints, the efficacy of coitus interruptus in preventing an unwanted pregnancy is rather low (see Table 31.1).

REVERSIBLE METHODS OF CONTRACEPTION USED BY MEN

Condom

Modern condoms, which are made of latex, prelubricated, and supplied in hermetically sealed aluminium sachets, are cheap, efficient and hardly noticeable to either partner. Their advantages are that they can be obtained from a variety of outlets without a doctor’s prescription, and that they offer some protection against sexually transmitted diseases, including the human papilloma virus, chlamydia and the human immunodeficiency virus (HIV). The disadvantage of condoms is that many younger men refuse to use them in the belief that they reduce sexual pleasure and may burst during use.

The pregnancy rate following condom use relates to usage, to the way the condom is put on the penis, and how it is held on after penile detumescence. If consulted by a woman or her partner the doctor should explain how a condom should be used (Fig. 31.3).

Fig. 31.3 Information for patients: how to use a condom, (A) Open the packet carefully, and do not unroll the condom before putting it on. (B) Semen can leak out soon after the penis becomes erect, prior to ejaculation. To prevent pregnancy or infection, the condom must be put on before any sexual contact takes place. (C) Ensure that the condom is the right way up. Squeeze the teat on the tip of the condom and hold it against the tip of the penis, (D), unroll the condom all the way to the base of the penis. (E) After ejaculation, the penis should be withdrawn before the erection is totally lost. When withdrawing, hold on to the condom. (F) Do not allow the condom or penis to come into contact with the woman’s genital area, and carefully dispose of the condom.

REVERSIBLE METHODS OF CONTRACEPTION USED BY WOMEN

Women have more choices of reversible or temporary contraception than men. They may choose:

• Barrier methods – the vaginal diaphragm, the cervical cap

• Hormonal contraceptives – the pill, patches, injectables and implants

• The intra-uterine device (IUCD).

Barrier methods

Vaginal diaphragm and the cervical cap

The vaginal diaphragm and the cervical cap consist of a thin plastic or latex dome attached to a circular flat, coiled or arching spring rim. The vaginal diaphragm is easier to use than the cervical cap, as it fits diagonally across the vagina. The correct size of the diaphragm is determined by a medical practitioner examining the woman vaginally, by inserting the index and middle fingers as far as they will go into the posterior vaginal fornix and noting how far the index finger reaches behind the symphysis pubis. The diaphragm is made in sizes from 50 mm to 100 mm, in 5 mm steps. After measuring the vagina, the doctor inserts a series of diaphragms or fitting rings until the most appropriate size is found.

Using a diaphragm or a cervical cap requires practice, and after teaching a woman how to use it (Fig. 31.4) many doctors ask the woman to learn the technique at home and return with the diaphragm or cap in place for checking.

Fig. 31.4 The use of the vaginal diaphragm.

When the woman is confident about the technique, she inserts the diaphragm each day or at any convenient time before sexual intercourse is anticipated. It should not be removed for cleaning until at least 6 hours after the last ejaculation. Some women choose to smear a nonoxynol-9 spermicidal cream around the rim, but whether this adds to the effectiveness of the diaphragm in preventing pregnancy is uncertain. It is known to destroy HIV to some extent, which is a benefit.

If a woman chooses a cervical cap she must have a healthy, short cervix. Fitting is carried out by a medical practitioner. The technique of insertion and removal is the same as that for the vaginal diaphragm.

Hormonal contraceptives

Hormonal contraceptives contain oestrogen and a progestogen (combined oral contraceptives) or progestogen alone. Oestrogen suppresses follicle-stimulating hormone (FSH) secretion and reduces luteinizing hormone (LH) secretion, and in this way prevents ovulation. The progestogen further suppresses LH release, alters the quality of the cervical mucus, rendering it less penetrable to sperm, and produces endometrial changes culminating in glandular exhaustion. Importantly, the progestogen also permits a withdrawal bleed, which is regular in onset, short in duration and light in amount.

Combined oral contraceptive (COC)

These formulations are chosen by most contraceptive users as they are effective in preventing pregnancy and are easy to take. Most types of currently available COCs contain less than 50 µg of ethinyl oestradiol per dose (one type contains mestranol, which is rapidly converted into ethinyl oestradiol), and one of several progestogens. These are called low-dose COCs.

Buy Membership for Obstetrics & Gynecology Category to continue reading. Learn more here

Related

Llewellyn-Jones Fundamentals of Obstetrics and Gynaecology